io_uring: synchronise ev_posted() with waitqueues

[linux.git] / fs / io_uring.c

// SPDX-License-Identifier: GPL-2.0
/*
 * Shared application/kernel submission and completion ring pairs, for
 * supporting fast/efficient IO.
 *
 * A note on the read/write ordering memory barriers that are matched between
 * the application and kernel side.
 *
 * After the application reads the CQ ring tail, it must use an
 * appropriate smp_rmb() to pair with the smp_wmb() the kernel uses
 * before writing the tail (using smp_load_acquire to read the tail will
 * do). It also needs a smp_mb() before updating CQ head (ordering the
 * entry load(s) with the head store), pairing with an implicit barrier
 * through a control-dependency in io_get_cqring (smp_store_release to
 * store head will do). Failure to do so could lead to reading invalid
 * CQ entries.
 *
 * Likewise, the application must use an appropriate smp_wmb() before
 * writing the SQ tail (ordering SQ entry stores with the tail store),
 * which pairs with smp_load_acquire in io_get_sqring (smp_store_release
 * to store the tail will do). And it needs a barrier ordering the SQ
 * head load before writing new SQ entries (smp_load_acquire to read
 * head will do).
 *
 * When using the SQ poll thread (IORING_SETUP_SQPOLL), the application
 * needs to check the SQ flags for IORING_SQ_NEED_WAKEUP *after*
 * updating the SQ tail; a full memory barrier smp_mb() is needed
 * between.
 *
 * Also see the examples in the liburing library:
 *
 *      git://git.kernel.dk/liburing
 *
 * io_uring also uses READ/WRITE_ONCE() for _any_ store or load that happens
 * from data shared between the kernel and application. This is done both
 * for ordering purposes, but also to ensure that once a value is loaded from
 * data that the application could potentially modify, it remains stable.
 *
 * Copyright (C) 2018-2019 Jens Axboe
 * Copyright (c) 2018-2019 Christoph Hellwig
 */
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/errno.h>
#include <linux/syscalls.h>
#include <linux/compat.h>
#include <net/compat.h>
#include <linux/refcount.h>
#include <linux/uio.h>
#include <linux/bits.h>

#include <linux/sched/signal.h>
#include <linux/fs.h>
#include <linux/file.h>
#include <linux/fdtable.h>
#include <linux/mm.h>
#include <linux/mman.h>
#include <linux/percpu.h>
#include <linux/slab.h>
#include <linux/kthread.h>
#include <linux/blkdev.h>
#include <linux/bvec.h>
#include <linux/net.h>
#include <net/sock.h>
#include <net/af_unix.h>
#include <net/scm.h>
#include <linux/anon_inodes.h>
#include <linux/sched/mm.h>
#include <linux/uaccess.h>
#include <linux/nospec.h>
#include <linux/sizes.h>
#include <linux/hugetlb.h>
#include <linux/highmem.h>
#include <linux/namei.h>
#include <linux/fsnotify.h>
#include <linux/fadvise.h>
#include <linux/eventpoll.h>
#include <linux/fs_struct.h>
#include <linux/splice.h>
#include <linux/task_work.h>
#include <linux/pagemap.h>
#include <linux/io_uring.h>
#include <linux/blk-cgroup.h>
#include <linux/audit.h>

#define CREATE_TRACE_POINTS
#include <trace/events/io_uring.h>

#include <uapi/linux/io_uring.h>

#include "internal.h"
#include "io-wq.h"

#define IORING_MAX_ENTRIES      32768
#define IORING_MAX_CQ_ENTRIES   (2 * IORING_MAX_ENTRIES)

/*
 * Shift of 9 is 512 entries, or exactly one page on 64-bit archs
 */
#define IORING_FILE_TABLE_SHIFT 9
#define IORING_MAX_FILES_TABLE  (1U << IORING_FILE_TABLE_SHIFT)
#define IORING_FILE_TABLE_MASK  (IORING_MAX_FILES_TABLE - 1)
#define IORING_MAX_FIXED_FILES  (64 * IORING_MAX_FILES_TABLE)
#define IORING_MAX_RESTRICTIONS (IORING_RESTRICTION_LAST + \
                                 IORING_REGISTER_LAST + IORING_OP_LAST)

struct io_uring {
        u32 head ____cacheline_aligned_in_smp;
        u32 tail ____cacheline_aligned_in_smp;
};

/*
 * This data is shared with the application through the mmap at offsets
 * IORING_OFF_SQ_RING and IORING_OFF_CQ_RING.
 *
 * The offsets to the member fields are published through struct
 * io_sqring_offsets when calling io_uring_setup.
 */
struct io_rings {
        /*
         * Head and tail offsets into the ring; the offsets need to be
         * masked to get valid indices.
         *
         * The kernel controls head of the sq ring and the tail of the cq ring,
         * and the application controls tail of the sq ring and the head of the
         * cq ring.
         */
        struct io_uring         sq, cq;
        /*
         * Bitmasks to apply to head and tail offsets (constant, equals
         * ring_entries - 1)
         */
        u32                     sq_ring_mask, cq_ring_mask;
        /* Ring sizes (constant, power of 2) */
        u32                     sq_ring_entries, cq_ring_entries;
        /*
         * Number of invalid entries dropped by the kernel due to
         * invalid index stored in array
         *
         * Written by the kernel, shouldn't be modified by the
         * application (i.e. get number of "new events" by comparing to
         * cached value).
         *
         * After a new SQ head value was read by the application this
         * counter includes all submissions that were dropped reaching
         * the new SQ head (and possibly more).
         */
        u32                     sq_dropped;
        /*
         * Runtime SQ flags
         *
         * Written by the kernel, shouldn't be modified by the
         * application.
         *
         * The application needs a full memory barrier before checking
         * for IORING_SQ_NEED_WAKEUP after updating the sq tail.
         */
        u32                     sq_flags;
        /*
         * Runtime CQ flags
         *
         * Written by the application, shouldn't be modified by the
         * kernel.
         */
        u32                     cq_flags;
        /*
         * Number of completion events lost because the queue was full;
         * this should be avoided by the application by making sure
         * there are not more requests pending than there is space in
         * the completion queue.
         *
         * Written by the kernel, shouldn't be modified by the
         * application (i.e. get number of "new events" by comparing to
         * cached value).
         *
         * As completion events come in out of order this counter is not
         * ordered with any other data.
         */
        u32                     cq_overflow;
        /*
         * Ring buffer of completion events.
         *
         * The kernel writes completion events fresh every time they are
         * produced, so the application is allowed to modify pending
         * entries.
         */
        struct io_uring_cqe     cqes[] ____cacheline_aligned_in_smp;
};

struct io_mapped_ubuf {
        u64             ubuf;
        size_t          len;
        struct          bio_vec *bvec;
        unsigned int    nr_bvecs;
        unsigned long   acct_pages;
};

struct fixed_file_table {
        struct file             **files;
};

struct fixed_file_ref_node {
        struct percpu_ref               refs;
        struct list_head                node;
        struct list_head                file_list;
        struct fixed_file_data          *file_data;
        struct llist_node               llist;
        bool                            done;
};

struct fixed_file_data {
        struct fixed_file_table         *table;
        struct io_ring_ctx              *ctx;

        struct fixed_file_ref_node      *node;
        struct percpu_ref               refs;
        struct completion               done;
        struct list_head                ref_list;
        spinlock_t                      lock;
};

struct io_buffer {
        struct list_head list;
        __u64 addr;
        __s32 len;
        __u16 bid;
};

struct io_restriction {
        DECLARE_BITMAP(register_op, IORING_REGISTER_LAST);
        DECLARE_BITMAP(sqe_op, IORING_OP_LAST);
        u8 sqe_flags_allowed;
        u8 sqe_flags_required;
        bool registered;
};

struct io_sq_data {
        refcount_t              refs;
        struct mutex            lock;

        /* ctx's that are using this sqd */
        struct list_head        ctx_list;
        struct list_head        ctx_new_list;
        struct mutex            ctx_lock;

        struct task_struct      *thread;
        struct wait_queue_head  wait;

        unsigned                sq_thread_idle;
};

struct io_ring_ctx {
        struct {
                struct percpu_ref       refs;
        } ____cacheline_aligned_in_smp;

        struct {
                unsigned int            flags;
                unsigned int            compat: 1;
                unsigned int            limit_mem: 1;
                unsigned int            cq_overflow_flushed: 1;
                unsigned int            drain_next: 1;
                unsigned int            eventfd_async: 1;
                unsigned int            restricted: 1;

                /*
                 * Ring buffer of indices into array of io_uring_sqe, which is
                 * mmapped by the application using the IORING_OFF_SQES offset.
                 *
                 * This indirection could e.g. be used to assign fixed
                 * io_uring_sqe entries to operations and only submit them to
                 * the queue when needed.
                 *
                 * The kernel modifies neither the indices array nor the entries
                 * array.
                 */
                u32                     *sq_array;
                unsigned                cached_sq_head;
                unsigned                sq_entries;
                unsigned                sq_mask;
                unsigned                sq_thread_idle;
                unsigned                cached_sq_dropped;
                unsigned                cached_cq_overflow;
                unsigned long           sq_check_overflow;

                struct list_head        defer_list;
                struct list_head        timeout_list;
                struct list_head        cq_overflow_list;

                struct io_uring_sqe     *sq_sqes;
        } ____cacheline_aligned_in_smp;

        struct io_rings *rings;

        /* IO offload */
        struct io_wq            *io_wq;

        /*
         * For SQPOLL usage - we hold a reference to the parent task, so we
         * have access to the ->files
         */
        struct task_struct      *sqo_task;

        /* Only used for accounting purposes */
        struct mm_struct        *mm_account;

#ifdef CONFIG_BLK_CGROUP
        struct cgroup_subsys_state      *sqo_blkcg_css;
#endif

        struct io_sq_data       *sq_data;       /* if using sq thread polling */

        struct wait_queue_head  sqo_sq_wait;
        struct list_head        sqd_list;

        /*
         * If used, fixed file set. Writers must ensure that ->refs is dead,
         * readers must ensure that ->refs is alive as long as the file* is
         * used. Only updated through io_uring_register(2).
         */
        struct fixed_file_data  *file_data;
        unsigned                nr_user_files;

        /* if used, fixed mapped user buffers */
        unsigned                nr_user_bufs;
        struct io_mapped_ubuf   *user_bufs;

        struct user_struct      *user;

        const struct cred       *creds;

#ifdef CONFIG_AUDIT
        kuid_t                  loginuid;
        unsigned int            sessionid;
#endif

        struct completion       ref_comp;
        struct completion       sq_thread_comp;

        /* if all else fails... */
        struct io_kiocb         *fallback_req;

#if defined(CONFIG_UNIX)
        struct socket           *ring_sock;
#endif

        struct idr              io_buffer_idr;

        struct idr              personality_idr;

        struct {
                unsigned                cached_cq_tail;
                unsigned                cq_entries;
                unsigned                cq_mask;
                atomic_t                cq_timeouts;
                unsigned long           cq_check_overflow;
                struct wait_queue_head  cq_wait;
                struct fasync_struct    *cq_fasync;
                struct eventfd_ctx      *cq_ev_fd;
        } ____cacheline_aligned_in_smp;

        struct {
                struct mutex            uring_lock;
                wait_queue_head_t       wait;
        } ____cacheline_aligned_in_smp;

        struct {
                spinlock_t              completion_lock;

                /*
                 * ->iopoll_list is protected by the ctx->uring_lock for
                 * io_uring instances that don't use IORING_SETUP_SQPOLL.
                 * For SQPOLL, only the single threaded io_sq_thread() will
                 * manipulate the list, hence no extra locking is needed there.
                 */
                struct list_head        iopoll_list;
                struct hlist_head       *cancel_hash;
                unsigned                cancel_hash_bits;
                bool                    poll_multi_file;

                spinlock_t              inflight_lock;
                struct list_head        inflight_list;
        } ____cacheline_aligned_in_smp;

        struct delayed_work             file_put_work;
        struct llist_head               file_put_llist;

        struct work_struct              exit_work;
        struct io_restriction           restrictions;
};

/*
 * First field must be the file pointer in all the
 * iocb unions! See also 'struct kiocb' in <linux/fs.h>
 */
struct io_poll_iocb {
        struct file                     *file;
        struct wait_queue_head          *head;
        __poll_t                        events;
        bool                            done;
        bool                            canceled;
        struct wait_queue_entry         wait;
};

struct io_poll_remove {
        struct file                     *file;
        u64                             addr;
};

struct io_close {
        struct file                     *file;
        struct file                     *put_file;
        int                             fd;
};

struct io_timeout_data {
        struct io_kiocb                 *req;
        struct hrtimer                  timer;
        struct timespec64               ts;
        enum hrtimer_mode               mode;
};

struct io_accept {
        struct file                     *file;
        struct sockaddr __user          *addr;
        int __user                      *addr_len;
        int                             flags;
        unsigned long                   nofile;
};

struct io_sync {
        struct file                     *file;
        loff_t                          len;
        loff_t                          off;
        int                             flags;
        int                             mode;
};

struct io_cancel {
        struct file                     *file;
        u64                             addr;
};

struct io_timeout {
        struct file                     *file;
        u32                             off;
        u32                             target_seq;
        struct list_head                list;
        /* head of the link, used by linked timeouts only */
        struct io_kiocb                 *head;
};

struct io_timeout_rem {
        struct file                     *file;
        u64                             addr;

        /* timeout update */
        struct timespec64               ts;
        u32                             flags;
};

struct io_rw {
        /* NOTE: kiocb has the file as the first member, so don't do it here */
        struct kiocb                    kiocb;
        u64                             addr;
        u64                             len;
};

struct io_connect {
        struct file                     *file;
        struct sockaddr __user          *addr;
        int                             addr_len;
};

struct io_sr_msg {
        struct file                     *file;
        union {
                struct user_msghdr __user *umsg;
                void __user             *buf;
        };
        int                             msg_flags;
        int                             bgid;
        size_t                          len;
        struct io_buffer                *kbuf;
};

struct io_open {
        struct file                     *file;
        int                             dfd;
        bool                            ignore_nonblock;
        struct filename                 *filename;
        struct open_how                 how;
        unsigned long                   nofile;
};

struct io_files_update {
        struct file                     *file;
        u64                             arg;
        u32                             nr_args;
        u32                             offset;
};

struct io_fadvise {
        struct file                     *file;
        u64                             offset;
        u32                             len;
        u32                             advice;
};

struct io_madvise {
        struct file                     *file;
        u64                             addr;
        u32                             len;
        u32                             advice;
};

struct io_epoll {
        struct file                     *file;
        int                             epfd;
        int                             op;
        int                             fd;
        struct epoll_event              event;
};

struct io_splice {
        struct file                     *file_out;
        struct file                     *file_in;
        loff_t                          off_out;
        loff_t                          off_in;
        u64                             len;
        unsigned int                    flags;
};

struct io_provide_buf {
        struct file                     *file;
        __u64                           addr;
        __s32                           len;
        __u32                           bgid;
        __u16                           nbufs;
        __u16                           bid;
};

struct io_statx {
        struct file                     *file;
        int                             dfd;
        unsigned int                    mask;
        unsigned int                    flags;
        const char __user               *filename;
        struct statx __user             *buffer;
};

struct io_shutdown {
        struct file                     *file;
        int                             how;
};

struct io_rename {
        struct file                     *file;
        int                             old_dfd;
        int                             new_dfd;
        struct filename                 *oldpath;
        struct filename                 *newpath;
        int                             flags;
};

struct io_unlink {
        struct file                     *file;
        int                             dfd;
        int                             flags;
        struct filename                 *filename;
};

struct io_completion {
        struct file                     *file;
        struct list_head                list;
        int                             cflags;
};

struct io_async_connect {
        struct sockaddr_storage         address;
};

struct io_async_msghdr {
        struct iovec                    fast_iov[UIO_FASTIOV];
        struct iovec                    *iov;
        struct sockaddr __user          *uaddr;
        struct msghdr                   msg;
        struct sockaddr_storage         addr;
};

struct io_async_rw {
        struct iovec                    fast_iov[UIO_FASTIOV];
        const struct iovec              *free_iovec;
        struct iov_iter                 iter;
        size_t                          bytes_done;
        struct wait_page_queue          wpq;
};

enum {
        REQ_F_FIXED_FILE_BIT    = IOSQE_FIXED_FILE_BIT,
        REQ_F_IO_DRAIN_BIT      = IOSQE_IO_DRAIN_BIT,
        REQ_F_LINK_BIT          = IOSQE_IO_LINK_BIT,
        REQ_F_HARDLINK_BIT      = IOSQE_IO_HARDLINK_BIT,
        REQ_F_FORCE_ASYNC_BIT   = IOSQE_ASYNC_BIT,
        REQ_F_BUFFER_SELECT_BIT = IOSQE_BUFFER_SELECT_BIT,

        REQ_F_FAIL_LINK_BIT,
        REQ_F_INFLIGHT_BIT,
        REQ_F_CUR_POS_BIT,
        REQ_F_NOWAIT_BIT,
        REQ_F_LINK_TIMEOUT_BIT,
        REQ_F_ISREG_BIT,
        REQ_F_NEED_CLEANUP_BIT,
        REQ_F_POLLED_BIT,
        REQ_F_BUFFER_SELECTED_BIT,
        REQ_F_NO_FILE_TABLE_BIT,
        REQ_F_WORK_INITIALIZED_BIT,
        REQ_F_LTIMEOUT_ACTIVE_BIT,

        /* not a real bit, just to check we're not overflowing the space */
        __REQ_F_LAST_BIT,
};

enum {
        /* ctx owns file */
        REQ_F_FIXED_FILE        = BIT(REQ_F_FIXED_FILE_BIT),
        /* drain existing IO first */
        REQ_F_IO_DRAIN          = BIT(REQ_F_IO_DRAIN_BIT),
        /* linked sqes */
        REQ_F_LINK              = BIT(REQ_F_LINK_BIT),
        /* doesn't sever on completion < 0 */
        REQ_F_HARDLINK          = BIT(REQ_F_HARDLINK_BIT),
        /* IOSQE_ASYNC */
        REQ_F_FORCE_ASYNC       = BIT(REQ_F_FORCE_ASYNC_BIT),
        /* IOSQE_BUFFER_SELECT */
        REQ_F_BUFFER_SELECT     = BIT(REQ_F_BUFFER_SELECT_BIT),

        /* fail rest of links */
        REQ_F_FAIL_LINK         = BIT(REQ_F_FAIL_LINK_BIT),
        /* on inflight list */
        REQ_F_INFLIGHT          = BIT(REQ_F_INFLIGHT_BIT),
        /* read/write uses file position */
        REQ_F_CUR_POS           = BIT(REQ_F_CUR_POS_BIT),
        /* must not punt to workers */
        REQ_F_NOWAIT            = BIT(REQ_F_NOWAIT_BIT),
        /* has or had linked timeout */
        REQ_F_LINK_TIMEOUT      = BIT(REQ_F_LINK_TIMEOUT_BIT),
        /* regular file */
        REQ_F_ISREG             = BIT(REQ_F_ISREG_BIT),
        /* needs cleanup */
        REQ_F_NEED_CLEANUP      = BIT(REQ_F_NEED_CLEANUP_BIT),
        /* already went through poll handler */
        REQ_F_POLLED            = BIT(REQ_F_POLLED_BIT),
        /* buffer already selected */
        REQ_F_BUFFER_SELECTED   = BIT(REQ_F_BUFFER_SELECTED_BIT),
        /* doesn't need file table for this request */
        REQ_F_NO_FILE_TABLE     = BIT(REQ_F_NO_FILE_TABLE_BIT),
        /* io_wq_work is initialized */
        REQ_F_WORK_INITIALIZED  = BIT(REQ_F_WORK_INITIALIZED_BIT),
        /* linked timeout is active, i.e. prepared by link's head */
        REQ_F_LTIMEOUT_ACTIVE   = BIT(REQ_F_LTIMEOUT_ACTIVE_BIT),
};

struct async_poll {
        struct io_poll_iocb     poll;
        struct io_poll_iocb     *double_poll;
};

/*
 * NOTE! Each of the iocb union members has the file pointer
 * as the first entry in their struct definition. So you can
 * access the file pointer through any of the sub-structs,
 * or directly as just 'ki_filp' in this struct.
 */
struct io_kiocb {
        union {
                struct file             *file;
                struct io_rw            rw;
                struct io_poll_iocb     poll;
                struct io_poll_remove   poll_remove;
                struct io_accept        accept;
                struct io_sync          sync;
                struct io_cancel        cancel;
                struct io_timeout       timeout;
                struct io_timeout_rem   timeout_rem;
                struct io_connect       connect;
                struct io_sr_msg        sr_msg;
                struct io_open          open;
                struct io_close         close;
                struct io_files_update  files_update;
                struct io_fadvise       fadvise;
                struct io_madvise       madvise;
                struct io_epoll         epoll;
                struct io_splice        splice;
                struct io_provide_buf   pbuf;
                struct io_statx         statx;
                struct io_shutdown      shutdown;
                struct io_rename        rename;
                struct io_unlink        unlink;
                /* use only after cleaning per-op data, see io_clean_op() */
                struct io_completion    compl;
        };

        /* opcode allocated if it needs to store data for async defer */
        void                            *async_data;
        u8                              opcode;
        /* polled IO has completed */
        u8                              iopoll_completed;

        u16                             buf_index;
        u32                             result;

        struct io_ring_ctx              *ctx;
        unsigned int                    flags;
        refcount_t                      refs;
        struct task_struct              *task;
        u64                             user_data;

        struct io_kiocb                 *link;
        struct percpu_ref               *fixed_file_refs;

        /*
         * 1. used with ctx->iopoll_list with reads/writes
         * 2. to track reqs with ->files (see io_op_def::file_table)
         */
        struct list_head                inflight_entry;
        struct callback_head            task_work;
        /* for polled requests, i.e. IORING_OP_POLL_ADD and async armed poll */
        struct hlist_node               hash_node;
        struct async_poll               *apoll;
        struct io_wq_work               work;
};

struct io_defer_entry {
        struct list_head        list;
        struct io_kiocb         *req;
        u32                     seq;
};

#define IO_IOPOLL_BATCH                 8

struct io_comp_state {
        unsigned int            nr;
        struct list_head        list;
        struct io_ring_ctx      *ctx;
};

struct io_submit_state {
        struct blk_plug         plug;

        /*
         * io_kiocb alloc cache
         */
        void                    *reqs[IO_IOPOLL_BATCH];
        unsigned int            free_reqs;

        bool                    plug_started;

        /*
         * Batch completion logic
         */
        struct io_comp_state    comp;

        /*
         * File reference cache
         */
        struct file             *file;
        unsigned int            fd;
        unsigned int            file_refs;
        unsigned int            ios_left;
};

struct io_op_def {
        /* needs req->file assigned */
        unsigned                needs_file : 1;
        /* don't fail if file grab fails */
        unsigned                needs_file_no_error : 1;
        /* hash wq insertion if file is a regular file */
        unsigned                hash_reg_file : 1;
        /* unbound wq insertion if file is a non-regular file */
        unsigned                unbound_nonreg_file : 1;
        /* opcode is not supported by this kernel */
        unsigned                not_supported : 1;
        /* set if opcode supports polled "wait" */
        unsigned                pollin : 1;
        unsigned                pollout : 1;
        /* op supports buffer selection */
        unsigned                buffer_select : 1;
        /* must always have async data allocated */
        unsigned                needs_async_data : 1;
        /* should block plug */
        unsigned                plug : 1;
        /* size of async data needed, if any */
        unsigned short          async_size;
        unsigned                work_flags;
};

static const struct io_op_def io_op_defs[] = {
        [IORING_OP_NOP] = {},
        [IORING_OP_READV] = {
                .needs_file             = 1,
                .unbound_nonreg_file    = 1,
                .pollin                 = 1,
                .buffer_select          = 1,
                .needs_async_data       = 1,
                .plug                   = 1,
                .async_size             = sizeof(struct io_async_rw),
                .work_flags             = IO_WQ_WORK_MM | IO_WQ_WORK_BLKCG,
        },
        [IORING_OP_WRITEV] = {
                .needs_file             = 1,
                .hash_reg_file          = 1,
                .unbound_nonreg_file    = 1,
                .pollout                = 1,
                .needs_async_data       = 1,
                .plug                   = 1,
                .async_size             = sizeof(struct io_async_rw),
                .work_flags             = IO_WQ_WORK_MM | IO_WQ_WORK_BLKCG |
                                                IO_WQ_WORK_FSIZE,
        },
        [IORING_OP_FSYNC] = {
                .needs_file             = 1,
                .work_flags             = IO_WQ_WORK_BLKCG,
        },
        [IORING_OP_READ_FIXED] = {
                .needs_file             = 1,
                .unbound_nonreg_file    = 1,
                .pollin                 = 1,
                .plug                   = 1,
                .async_size             = sizeof(struct io_async_rw),
                .work_flags             = IO_WQ_WORK_BLKCG | IO_WQ_WORK_MM,
        },
        [IORING_OP_WRITE_FIXED] = {
                .needs_file             = 1,
                .hash_reg_file          = 1,
                .unbound_nonreg_file    = 1,
                .pollout                = 1,
                .plug                   = 1,
                .async_size             = sizeof(struct io_async_rw),
                .work_flags             = IO_WQ_WORK_BLKCG | IO_WQ_WORK_FSIZE |
                                                IO_WQ_WORK_MM,
        },
        [IORING_OP_POLL_ADD] = {
                .needs_file             = 1,
                .unbound_nonreg_file    = 1,
        },
        [IORING_OP_POLL_REMOVE] = {},
        [IORING_OP_SYNC_FILE_RANGE] = {
                .needs_file             = 1,
                .work_flags             = IO_WQ_WORK_BLKCG,
        },
        [IORING_OP_SENDMSG] = {
                .needs_file             = 1,
                .unbound_nonreg_file    = 1,
                .pollout                = 1,
                .needs_async_data       = 1,
                .async_size             = sizeof(struct io_async_msghdr),
                .work_flags             = IO_WQ_WORK_MM | IO_WQ_WORK_BLKCG,
        },
        [IORING_OP_RECVMSG] = {
                .needs_file             = 1,
                .unbound_nonreg_file    = 1,
                .pollin                 = 1,
                .buffer_select          = 1,
                .needs_async_data       = 1,
                .async_size             = sizeof(struct io_async_msghdr),
                .work_flags             = IO_WQ_WORK_MM | IO_WQ_WORK_BLKCG,
        },
        [IORING_OP_TIMEOUT] = {
                .needs_async_data       = 1,
                .async_size             = sizeof(struct io_timeout_data),
                .work_flags             = IO_WQ_WORK_MM,
        },
        [IORING_OP_TIMEOUT_REMOVE] = {
                /* used by timeout updates' prep() */
                .work_flags             = IO_WQ_WORK_MM,
        },
        [IORING_OP_ACCEPT] = {
                .needs_file             = 1,
                .unbound_nonreg_file    = 1,
                .pollin                 = 1,
                .work_flags             = IO_WQ_WORK_MM | IO_WQ_WORK_FILES,
        },
        [IORING_OP_ASYNC_CANCEL] = {},
        [IORING_OP_LINK_TIMEOUT] = {
                .needs_async_data       = 1,
                .async_size             = sizeof(struct io_timeout_data),
                .work_flags             = IO_WQ_WORK_MM,
        },
        [IORING_OP_CONNECT] = {
                .needs_file             = 1,
                .unbound_nonreg_file    = 1,
                .pollout                = 1,
                .needs_async_data       = 1,
                .async_size             = sizeof(struct io_async_connect),
                .work_flags             = IO_WQ_WORK_MM,
        },
        [IORING_OP_FALLOCATE] = {
                .needs_file             = 1,
                .work_flags             = IO_WQ_WORK_BLKCG | IO_WQ_WORK_FSIZE,
        },
        [IORING_OP_OPENAT] = {
                .work_flags             = IO_WQ_WORK_FILES | IO_WQ_WORK_BLKCG |
                                                IO_WQ_WORK_FS | IO_WQ_WORK_MM,
        },
        [IORING_OP_CLOSE] = {
                .needs_file             = 1,
                .needs_file_no_error    = 1,
                .work_flags             = IO_WQ_WORK_FILES | IO_WQ_WORK_BLKCG,
        },
        [IORING_OP_FILES_UPDATE] = {
                .work_flags             = IO_WQ_WORK_FILES | IO_WQ_WORK_MM,
        },
        [IORING_OP_STATX] = {
                .work_flags             = IO_WQ_WORK_FILES | IO_WQ_WORK_MM |
                                                IO_WQ_WORK_FS | IO_WQ_WORK_BLKCG,
        },
        [IORING_OP_READ] = {
                .needs_file             = 1,
                .unbound_nonreg_file    = 1,
                .pollin                 = 1,
                .buffer_select          = 1,
                .plug                   = 1,
                .async_size             = sizeof(struct io_async_rw),
                .work_flags             = IO_WQ_WORK_MM | IO_WQ_WORK_BLKCG,
        },
        [IORING_OP_WRITE] = {
                .needs_file             = 1,
                .unbound_nonreg_file    = 1,
                .pollout                = 1,
                .plug                   = 1,
                .async_size             = sizeof(struct io_async_rw),
                .work_flags             = IO_WQ_WORK_MM | IO_WQ_WORK_BLKCG |
                                                IO_WQ_WORK_FSIZE,
        },
        [IORING_OP_FADVISE] = {
                .needs_file             = 1,
                .work_flags             = IO_WQ_WORK_BLKCG,
        },
        [IORING_OP_MADVISE] = {
                .work_flags             = IO_WQ_WORK_MM | IO_WQ_WORK_BLKCG,
        },
        [IORING_OP_SEND] = {
                .needs_file             = 1,
                .unbound_nonreg_file    = 1,
                .pollout                = 1,
                .work_flags             = IO_WQ_WORK_MM | IO_WQ_WORK_BLKCG,
        },
        [IORING_OP_RECV] = {
                .needs_file             = 1,
                .unbound_nonreg_file    = 1,
                .pollin                 = 1,
                .buffer_select          = 1,
                .work_flags             = IO_WQ_WORK_MM | IO_WQ_WORK_BLKCG,
        },
        [IORING_OP_OPENAT2] = {
                .work_flags             = IO_WQ_WORK_FILES | IO_WQ_WORK_FS |
                                                IO_WQ_WORK_BLKCG | IO_WQ_WORK_MM,
        },
        [IORING_OP_EPOLL_CTL] = {
                .unbound_nonreg_file    = 1,
                .work_flags             = IO_WQ_WORK_FILES,
        },
        [IORING_OP_SPLICE] = {
                .needs_file             = 1,
                .hash_reg_file          = 1,
                .unbound_nonreg_file    = 1,
                .work_flags             = IO_WQ_WORK_BLKCG,
        },
        [IORING_OP_PROVIDE_BUFFERS] = {},
        [IORING_OP_REMOVE_BUFFERS] = {},
        [IORING_OP_TEE] = {
                .needs_file             = 1,
                .hash_reg_file          = 1,
                .unbound_nonreg_file    = 1,
        },
        [IORING_OP_SHUTDOWN] = {
                .needs_file             = 1,
        },
        [IORING_OP_RENAMEAT] = {
                .work_flags             = IO_WQ_WORK_MM | IO_WQ_WORK_FILES |
                                                IO_WQ_WORK_FS | IO_WQ_WORK_BLKCG,
        },
        [IORING_OP_UNLINKAT] = {
                .work_flags             = IO_WQ_WORK_MM | IO_WQ_WORK_FILES |
                                                IO_WQ_WORK_FS | IO_WQ_WORK_BLKCG,
        },
};

enum io_mem_account {
        ACCT_LOCKED,
        ACCT_PINNED,
};

static void __io_uring_cancel_task_requests(struct io_ring_ctx *ctx,
                                            struct task_struct *task);

static void destroy_fixed_file_ref_node(struct fixed_file_ref_node *ref_node);
static struct fixed_file_ref_node *alloc_fixed_file_ref_node(
                        struct io_ring_ctx *ctx);

static void __io_complete_rw(struct io_kiocb *req, long res, long res2,
                             struct io_comp_state *cs);
static void io_cqring_fill_event(struct io_kiocb *req, long res);
static void io_put_req(struct io_kiocb *req);
static void io_put_req_deferred(struct io_kiocb *req, int nr);
static void io_double_put_req(struct io_kiocb *req);
static struct io_kiocb *io_prep_linked_timeout(struct io_kiocb *req);
static void __io_queue_linked_timeout(struct io_kiocb *req);
static void io_queue_linked_timeout(struct io_kiocb *req);
static int __io_sqe_files_update(struct io_ring_ctx *ctx,
                                 struct io_uring_files_update *ip,
                                 unsigned nr_args);
static void __io_clean_op(struct io_kiocb *req);
static struct file *io_file_get(struct io_submit_state *state,
                                struct io_kiocb *req, int fd, bool fixed);
static void __io_queue_sqe(struct io_kiocb *req, struct io_comp_state *cs);
static void io_file_put_work(struct work_struct *work);

static ssize_t io_import_iovec(int rw, struct io_kiocb *req,
                               struct iovec **iovec, struct iov_iter *iter,
                               bool needs_lock);
static int io_setup_async_rw(struct io_kiocb *req, const struct iovec *iovec,
                             const struct iovec *fast_iov,
                             struct iov_iter *iter, bool force);

static struct kmem_cache *req_cachep;

static const struct file_operations io_uring_fops;

struct sock *io_uring_get_socket(struct file *file)
{
#if defined(CONFIG_UNIX)
        if (file->f_op == &io_uring_fops) {
                struct io_ring_ctx *ctx = file->private_data;

                return ctx->ring_sock->sk;
        }
#endif
        return NULL;
}
EXPORT_SYMBOL(io_uring_get_socket);

#define io_for_each_link(pos, head) \
        for (pos = (head); pos; pos = pos->link)

static inline void io_clean_op(struct io_kiocb *req)
{
        if (req->flags & (REQ_F_NEED_CLEANUP | REQ_F_BUFFER_SELECTED |
                          REQ_F_INFLIGHT))
                __io_clean_op(req);
}

static inline void io_set_resource_node(struct io_kiocb *req)
{
        struct io_ring_ctx *ctx = req->ctx;

        if (!req->fixed_file_refs) {
                req->fixed_file_refs = &ctx->file_data->node->refs;
                percpu_ref_get(req->fixed_file_refs);
        }
}

static bool io_match_task(struct io_kiocb *head,
                          struct task_struct *task,
                          struct files_struct *files)
{
        struct io_kiocb *req;

        if (task && head->task != task)
                return false;
        if (!files)
                return true;

        io_for_each_link(req, head) {
                if ((req->flags & REQ_F_WORK_INITIALIZED) &&
                    (req->work.flags & IO_WQ_WORK_FILES) &&
                    req->work.identity->files == files)
                        return true;
        }
        return false;
}

static void io_sq_thread_drop_mm_files(void)
{
        struct files_struct *files = current->files;
        struct mm_struct *mm = current->mm;

        if (mm) {
                kthread_unuse_mm(mm);
                mmput(mm);
                current->mm = NULL;
        }
        if (files) {
                struct nsproxy *nsproxy = current->nsproxy;

                task_lock(current);
                current->files = NULL;
                current->nsproxy = NULL;
                task_unlock(current);
                put_files_struct(files);
                put_nsproxy(nsproxy);
        }
}

static int __io_sq_thread_acquire_files(struct io_ring_ctx *ctx)
{
        if (!current->files) {
                struct files_struct *files;
                struct nsproxy *nsproxy;

                task_lock(ctx->sqo_task);
                files = ctx->sqo_task->files;
                if (!files) {
                        task_unlock(ctx->sqo_task);
                        return -EOWNERDEAD;
                }
                atomic_inc(&files->count);
                get_nsproxy(ctx->sqo_task->nsproxy);
                nsproxy = ctx->sqo_task->nsproxy;
                task_unlock(ctx->sqo_task);

                task_lock(current);
                current->files = files;
                current->nsproxy = nsproxy;
                task_unlock(current);
        }
        return 0;
}

static int __io_sq_thread_acquire_mm(struct io_ring_ctx *ctx)
{
        struct mm_struct *mm;

        if (current->mm)
                return 0;

        /* Should never happen */
        if (unlikely(!(ctx->flags & IORING_SETUP_SQPOLL)))
                return -EFAULT;

        task_lock(ctx->sqo_task);
        mm = ctx->sqo_task->mm;
        if (unlikely(!mm || !mmget_not_zero(mm)))
                mm = NULL;
        task_unlock(ctx->sqo_task);

        if (mm) {
                kthread_use_mm(mm);
                return 0;
        }

        return -EFAULT;
}

static int io_sq_thread_acquire_mm_files(struct io_ring_ctx *ctx,
                                         struct io_kiocb *req)
{
        const struct io_op_def *def = &io_op_defs[req->opcode];
        int ret;

        if (def->work_flags & IO_WQ_WORK_MM) {
                ret = __io_sq_thread_acquire_mm(ctx);
                if (unlikely(ret))
                        return ret;
        }

        if (def->needs_file || (def->work_flags & IO_WQ_WORK_FILES)) {
                ret = __io_sq_thread_acquire_files(ctx);
                if (unlikely(ret))
                        return ret;
        }

        return 0;
}

static void io_sq_thread_associate_blkcg(struct io_ring_ctx *ctx,
                                         struct cgroup_subsys_state **cur_css)

{
#ifdef CONFIG_BLK_CGROUP
        /* puts the old one when swapping */
        if (*cur_css != ctx->sqo_blkcg_css) {
                kthread_associate_blkcg(ctx->sqo_blkcg_css);
                *cur_css = ctx->sqo_blkcg_css;
        }
#endif
}

static void io_sq_thread_unassociate_blkcg(void)
{
#ifdef CONFIG_BLK_CGROUP
        kthread_associate_blkcg(NULL);
#endif
}

static inline void req_set_fail_links(struct io_kiocb *req)
{
        if ((req->flags & (REQ_F_LINK | REQ_F_HARDLINK)) == REQ_F_LINK)
                req->flags |= REQ_F_FAIL_LINK;
}

/*
 * None of these are dereferenced, they are simply used to check if any of
 * them have changed. If we're under current and check they are still the
 * same, we're fine to grab references to them for actual out-of-line use.
 */
static void io_init_identity(struct io_identity *id)
{
        id->files = current->files;
        id->mm = current->mm;
#ifdef CONFIG_BLK_CGROUP
        rcu_read_lock();
        id->blkcg_css = blkcg_css();
        rcu_read_unlock();
#endif
        id->creds = current_cred();
        id->nsproxy = current->nsproxy;
        id->fs = current->fs;
        id->fsize = rlimit(RLIMIT_FSIZE);
#ifdef CONFIG_AUDIT
        id->loginuid = current->loginuid;
        id->sessionid = current->sessionid;
#endif
        refcount_set(&id->count, 1);
}

static inline void __io_req_init_async(struct io_kiocb *req)
{
        memset(&req->work, 0, sizeof(req->work));
        req->flags |= REQ_F_WORK_INITIALIZED;
}

/*
 * Note: must call io_req_init_async() for the first time you
 * touch any members of io_wq_work.
 */
static inline void io_req_init_async(struct io_kiocb *req)
{
        struct io_uring_task *tctx = current->io_uring;

        if (req->flags & REQ_F_WORK_INITIALIZED)
                return;

        __io_req_init_async(req);

        /* Grab a ref if this isn't our static identity */
        req->work.identity = tctx->identity;
        if (tctx->identity != &tctx->__identity)
                refcount_inc(&req->work.identity->count);
}

static inline bool io_async_submit(struct io_ring_ctx *ctx)
{
        return ctx->flags & IORING_SETUP_SQPOLL;
}

static void io_ring_ctx_ref_free(struct percpu_ref *ref)
{
        struct io_ring_ctx *ctx = container_of(ref, struct io_ring_ctx, refs);

        complete(&ctx->ref_comp);
}

static inline bool io_is_timeout_noseq(struct io_kiocb *req)
{
        return !req->timeout.off;
}

static struct io_ring_ctx *io_ring_ctx_alloc(struct io_uring_params *p)
{
        struct io_ring_ctx *ctx;
        int hash_bits;

        ctx = kzalloc(sizeof(*ctx), GFP_KERNEL);
        if (!ctx)
                return NULL;

        ctx->fallback_req = kmem_cache_alloc(req_cachep, GFP_KERNEL);
        if (!ctx->fallback_req)
                goto err;

        /*
         * Use 5 bits less than the max cq entries, that should give us around
         * 32 entries per hash list if totally full and uniformly spread.
         */
        hash_bits = ilog2(p->cq_entries);
        hash_bits -= 5;
        if (hash_bits <= 0)
                hash_bits = 1;
        ctx->cancel_hash_bits = hash_bits;
        ctx->cancel_hash = kmalloc((1U << hash_bits) * sizeof(struct hlist_head),
                                        GFP_KERNEL);
        if (!ctx->cancel_hash)
                goto err;
        __hash_init(ctx->cancel_hash, 1U << hash_bits);

        if (percpu_ref_init(&ctx->refs, io_ring_ctx_ref_free,
                            PERCPU_REF_ALLOW_REINIT, GFP_KERNEL))
                goto err;

        ctx->flags = p->flags;
        init_waitqueue_head(&ctx->sqo_sq_wait);
        INIT_LIST_HEAD(&ctx->sqd_list);
        init_waitqueue_head(&ctx->cq_wait);
        INIT_LIST_HEAD(&ctx->cq_overflow_list);
        init_completion(&ctx->ref_comp);
        init_completion(&ctx->sq_thread_comp);
        idr_init(&ctx->io_buffer_idr);
        idr_init(&ctx->personality_idr);
        mutex_init(&ctx->uring_lock);
        init_waitqueue_head(&ctx->wait);
        spin_lock_init(&ctx->completion_lock);
        INIT_LIST_HEAD(&ctx->iopoll_list);
        INIT_LIST_HEAD(&ctx->defer_list);
        INIT_LIST_HEAD(&ctx->timeout_list);
        spin_lock_init(&ctx->inflight_lock);
        INIT_LIST_HEAD(&ctx->inflight_list);
        INIT_DELAYED_WORK(&ctx->file_put_work, io_file_put_work);
        init_llist_head(&ctx->file_put_llist);
        return ctx;
err:
        if (ctx->fallback_req)
                kmem_cache_free(req_cachep, ctx->fallback_req);
        kfree(ctx->cancel_hash);
        kfree(ctx);
        return NULL;
}

static bool req_need_defer(struct io_kiocb *req, u32 seq)
{
        if (unlikely(req->flags & REQ_F_IO_DRAIN)) {
                struct io_ring_ctx *ctx = req->ctx;

                return seq != ctx->cached_cq_tail
                                + READ_ONCE(ctx->cached_cq_overflow);
        }

        return false;
}

static void __io_commit_cqring(struct io_ring_ctx *ctx)
{
        struct io_rings *rings = ctx->rings;

        /* order cqe stores with ring update */
        smp_store_release(&rings->cq.tail, ctx->cached_cq_tail);
}

static void io_put_identity(struct io_uring_task *tctx, struct io_kiocb *req)
{
        if (req->work.identity == &tctx->__identity)
                return;
        if (refcount_dec_and_test(&req->work.identity->count))
                kfree(req->work.identity);
}

static void io_req_clean_work(struct io_kiocb *req)
{
        if (!(req->flags & REQ_F_WORK_INITIALIZED))
                return;

        req->flags &= ~REQ_F_WORK_INITIALIZED;

        if (req->work.flags & IO_WQ_WORK_MM) {
                mmdrop(req->work.identity->mm);
                req->work.flags &= ~IO_WQ_WORK_MM;
        }
#ifdef CONFIG_BLK_CGROUP
        if (req->work.flags & IO_WQ_WORK_BLKCG) {
                css_put(req->work.identity->blkcg_css);
                req->work.flags &= ~IO_WQ_WORK_BLKCG;
        }
#endif
        if (req->work.flags & IO_WQ_WORK_CREDS) {
                put_cred(req->work.identity->creds);
                req->work.flags &= ~IO_WQ_WORK_CREDS;
        }
        if (req->work.flags & IO_WQ_WORK_FS) {
                struct fs_struct *fs = req->work.identity->fs;

                spin_lock(&req->work.identity->fs->lock);
                if (--fs->users)
                        fs = NULL;
                spin_unlock(&req->work.identity->fs->lock);
                if (fs)
                        free_fs_struct(fs);
                req->work.flags &= ~IO_WQ_WORK_FS;
        }

        io_put_identity(req->task->io_uring, req);
}

/*
 * Create a private copy of io_identity, since some fields don't match
 * the current context.
 */
static bool io_identity_cow(struct io_kiocb *req)
{
        struct io_uring_task *tctx = current->io_uring;
        const struct cred *creds = NULL;
        struct io_identity *id;

        if (req->work.flags & IO_WQ_WORK_CREDS)
                creds = req->work.identity->creds;

        id = kmemdup(req->work.identity, sizeof(*id), GFP_KERNEL);
        if (unlikely(!id)) {
                req->work.flags |= IO_WQ_WORK_CANCEL;
                return false;
        }

        /*
         * We can safely just re-init the creds we copied  Either the field
         * matches the current one, or we haven't grabbed it yet. The only
         * exception is ->creds, through registered personalities, so handle
         * that one separately.
         */
        io_init_identity(id);
        if (creds)
                id->creds = creds;

        /* add one for this request */
        refcount_inc(&id->count);

        /* drop tctx and req identity references, if needed */
        if (tctx->identity != &tctx->__identity &&
            refcount_dec_and_test(&tctx->identity->count))
                kfree(tctx->identity);
        if (req->work.identity != &tctx->__identity &&
            refcount_dec_and_test(&req->work.identity->count))
                kfree(req->work.identity);

        req->work.identity = id;
        tctx->identity = id;
        return true;
}

static bool io_grab_identity(struct io_kiocb *req)
{
        const struct io_op_def *def = &io_op_defs[req->opcode];
        struct io_identity *id = req->work.identity;
        struct io_ring_ctx *ctx = req->ctx;

        if (def->work_flags & IO_WQ_WORK_FSIZE) {
                if (id->fsize != rlimit(RLIMIT_FSIZE))
                        return false;
                req->work.flags |= IO_WQ_WORK_FSIZE;
        }
#ifdef CONFIG_BLK_CGROUP
        if (!(req->work.flags & IO_WQ_WORK_BLKCG) &&
            (def->work_flags & IO_WQ_WORK_BLKCG)) {
                rcu_read_lock();
                if (id->blkcg_css != blkcg_css()) {
                        rcu_read_unlock();
                        return false;
                }
                /*
                 * This should be rare, either the cgroup is dying or the task
                 * is moving cgroups. Just punt to root for the handful of ios.
                 */
                if (css_tryget_online(id->blkcg_css))
                        req->work.flags |= IO_WQ_WORK_BLKCG;
                rcu_read_unlock();
        }
#endif
        if (!(req->work.flags & IO_WQ_WORK_CREDS)) {
                if (id->creds != current_cred())
                        return false;
                get_cred(id->creds);
                req->work.flags |= IO_WQ_WORK_CREDS;
        }
#ifdef CONFIG_AUDIT
        if (!uid_eq(current->loginuid, id->loginuid) ||
            current->sessionid != id->sessionid)
                return false;
#endif
        if (!(req->work.flags & IO_WQ_WORK_FS) &&
            (def->work_flags & IO_WQ_WORK_FS)) {
                if (current->fs != id->fs)
                        return false;
                spin_lock(&id->fs->lock);
                if (!id->fs->in_exec) {
                        id->fs->users++;
                        req->work.flags |= IO_WQ_WORK_FS;
                } else {
                        req->work.flags |= IO_WQ_WORK_CANCEL;
                }
                spin_unlock(&current->fs->lock);
        }
        if (!(req->work.flags & IO_WQ_WORK_FILES) &&
            (def->work_flags & IO_WQ_WORK_FILES) &&
            !(req->flags & REQ_F_NO_FILE_TABLE)) {
                if (id->files != current->files ||
                    id->nsproxy != current->nsproxy)
                        return false;
                atomic_inc(&id->files->count);
                get_nsproxy(id->nsproxy);
                req->flags |= REQ_F_INFLIGHT;

                spin_lock_irq(&ctx->inflight_lock);
                list_add(&req->inflight_entry, &ctx->inflight_list);
                spin_unlock_irq(&ctx->inflight_lock);
                req->work.flags |= IO_WQ_WORK_FILES;
        }
        if (!(req->work.flags & IO_WQ_WORK_MM) &&
            (def->work_flags & IO_WQ_WORK_MM)) {
                if (id->mm != current->mm)
                        return false;
                mmgrab(id->mm);
                req->work.flags |= IO_WQ_WORK_MM;
        }

        return true;
}

static void io_prep_async_work(struct io_kiocb *req)
{
        const struct io_op_def *def = &io_op_defs[req->opcode];
        struct io_ring_ctx *ctx = req->ctx;

        io_req_init_async(req);

        if (req->flags & REQ_F_FORCE_ASYNC)
                req->work.flags |= IO_WQ_WORK_CONCURRENT;

        if (req->flags & REQ_F_ISREG) {
                if (def->hash_reg_file || (ctx->flags & IORING_SETUP_IOPOLL))
                        io_wq_hash_work(&req->work, file_inode(req->file));
        } else {
                if (def->unbound_nonreg_file)
                        req->work.flags |= IO_WQ_WORK_UNBOUND;
        }

        /* if we fail grabbing identity, we must COW, regrab, and retry */
        if (io_grab_identity(req))
                return;

        if (!io_identity_cow(req))
                return;

        /* can't fail at this point */
        if (!io_grab_identity(req))
                WARN_ON(1);
}

static void io_prep_async_link(struct io_kiocb *req)
{
        struct io_kiocb *cur;

        io_for_each_link(cur, req)
                io_prep_async_work(cur);
}

static struct io_kiocb *__io_queue_async_work(struct io_kiocb *req)
{
        struct io_ring_ctx *ctx = req->ctx;
        struct io_kiocb *link = io_prep_linked_timeout(req);

        trace_io_uring_queue_async_work(ctx, io_wq_is_hashed(&req->work), req,
                                        &req->work, req->flags);
        io_wq_enqueue(ctx->io_wq, &req->work);
        return link;
}

static void io_queue_async_work(struct io_kiocb *req)
{
        struct io_kiocb *link;

        /* init ->work of the whole link before punting */
        io_prep_async_link(req);
        link = __io_queue_async_work(req);

        if (link)
                io_queue_linked_timeout(link);
}

static void io_kill_timeout(struct io_kiocb *req)
{
        struct io_timeout_data *io = req->async_data;
        int ret;

        ret = hrtimer_try_to_cancel(&io->timer);
        if (ret != -1) {
                atomic_set(&req->ctx->cq_timeouts,
                        atomic_read(&req->ctx->cq_timeouts) + 1);
                list_del_init(&req->timeout.list);
                io_cqring_fill_event(req, 0);
                io_put_req_deferred(req, 1);
        }
}

/*
 * Returns true if we found and killed one or more timeouts
 */
static bool io_kill_timeouts(struct io_ring_ctx *ctx, struct task_struct *tsk,
                             struct files_struct *files)
{
        struct io_kiocb *req, *tmp;
        int canceled = 0;

        spin_lock_irq(&ctx->completion_lock);
        list_for_each_entry_safe(req, tmp, &ctx->timeout_list, timeout.list) {
                if (io_match_task(req, tsk, files)) {
                        io_kill_timeout(req);
                        canceled++;
                }
        }
        spin_unlock_irq(&ctx->completion_lock);
        return canceled != 0;
}

static void __io_queue_deferred(struct io_ring_ctx *ctx)
{
        do {
                struct io_defer_entry *de = list_first_entry(&ctx->defer_list,
                                                struct io_defer_entry, list);
                struct io_kiocb *link;

                if (req_need_defer(de->req, de->seq))
                        break;
                list_del_init(&de->list);
                /* punt-init is done before queueing for defer */
                link = __io_queue_async_work(de->req);
                if (link) {
                        __io_queue_linked_timeout(link);
                        /* drop submission reference */
                        io_put_req_deferred(link, 1);
                }
                kfree(de);
        } while (!list_empty(&ctx->defer_list));
}

static void io_flush_timeouts(struct io_ring_ctx *ctx)
{
        while (!list_empty(&ctx->timeout_list)) {
                struct io_kiocb *req = list_first_entry(&ctx->timeout_list,
                                                struct io_kiocb, timeout.list);

                if (io_is_timeout_noseq(req))
                        break;
                if (req->timeout.target_seq != ctx->cached_cq_tail
                                        - atomic_read(&ctx->cq_timeouts))
                        break;

                list_del_init(&req->timeout.list);
                io_kill_timeout(req);
        }
}

static void io_commit_cqring(struct io_ring_ctx *ctx)
{
        io_flush_timeouts(ctx);
        __io_commit_cqring(ctx);

        if (unlikely(!list_empty(&ctx->defer_list)))
                __io_queue_deferred(ctx);
}

static inline bool io_sqring_full(struct io_ring_ctx *ctx)
{
        struct io_rings *r = ctx->rings;

        return READ_ONCE(r->sq.tail) - ctx->cached_sq_head == r->sq_ring_entries;
}

static struct io_uring_cqe *io_get_cqring(struct io_ring_ctx *ctx)
{
        struct io_rings *rings = ctx->rings;
        unsigned tail;

        tail = ctx->cached_cq_tail;
        /*
         * writes to the cq entry need to come after reading head; the
         * control dependency is enough as we're using WRITE_ONCE to
         * fill the cq entry
         */
        if (tail - READ_ONCE(rings->cq.head) == rings->cq_ring_entries)
                return NULL;

        ctx->cached_cq_tail++;
        return &rings->cqes[tail & ctx->cq_mask];
}

static inline bool io_should_trigger_evfd(struct io_ring_ctx *ctx)
{
        if (!ctx->cq_ev_fd)
                return false;
        if (READ_ONCE(ctx->rings->cq_flags) & IORING_CQ_EVENTFD_DISABLED)
                return false;
        if (!ctx->eventfd_async)
                return true;
        return io_wq_current_is_worker();
}

static inline unsigned __io_cqring_events(struct io_ring_ctx *ctx)
{
        return ctx->cached_cq_tail - READ_ONCE(ctx->rings->cq.head);
}

static void io_cqring_ev_posted(struct io_ring_ctx *ctx)
{
        /* see waitqueue_active() comment */
        smp_mb();

        if (waitqueue_active(&ctx->wait))
                wake_up(&ctx->wait);
        if (ctx->sq_data && waitqueue_active(&ctx->sq_data->wait))
                wake_up(&ctx->sq_data->wait);
        if (io_should_trigger_evfd(ctx))
                eventfd_signal(ctx->cq_ev_fd, 1);
        if (waitqueue_active(&ctx->cq_wait)) {
                wake_up_interruptible(&ctx->cq_wait);
                kill_fasync(&ctx->cq_fasync, SIGIO, POLL_IN);
        }
}

static void io_cqring_ev_posted_iopoll(struct io_ring_ctx *ctx)
{
        /* see waitqueue_active() comment */
        smp_mb();

        if (ctx->flags & IORING_SETUP_SQPOLL) {
                if (waitqueue_active(&ctx->wait))
                        wake_up(&ctx->wait);
        }
        if (io_should_trigger_evfd(ctx))
                eventfd_signal(ctx->cq_ev_fd, 1);
        if (waitqueue_active(&ctx->cq_wait)) {
                wake_up_interruptible(&ctx->cq_wait);
                kill_fasync(&ctx->cq_fasync, SIGIO, POLL_IN);
        }
}

/* Returns true if there are no backlogged entries after the flush */
static bool __io_cqring_overflow_flush(struct io_ring_ctx *ctx, bool force,
                                       struct task_struct *tsk,
                                       struct files_struct *files)
{
        struct io_rings *rings = ctx->rings;
        struct io_kiocb *req, *tmp;
        struct io_uring_cqe *cqe;
        unsigned long flags;
        bool all_flushed;
        LIST_HEAD(list);

        if (!force && __io_cqring_events(ctx) == rings->cq_ring_entries)
                return false;

        spin_lock_irqsave(&ctx->completion_lock, flags);
        list_for_each_entry_safe(req, tmp, &ctx->cq_overflow_list, compl.list) {
                if (!io_match_task(req, tsk, files))
                        continue;

                cqe = io_get_cqring(ctx);
                if (!cqe && !force)
                        break;

                list_move(&req->compl.list, &list);
                if (cqe) {
                        WRITE_ONCE(cqe->user_data, req->user_data);
                        WRITE_ONCE(cqe->res, req->result);
                        WRITE_ONCE(cqe->flags, req->compl.cflags);
                } else {
                        ctx->cached_cq_overflow++;
                        WRITE_ONCE(ctx->rings->cq_overflow,
                                   ctx->cached_cq_overflow);
                }
        }

        all_flushed = list_empty(&ctx->cq_overflow_list);
        if (all_flushed) {
                clear_bit(0, &ctx->sq_check_overflow);
                clear_bit(0, &ctx->cq_check_overflow);
                ctx->rings->sq_flags &= ~IORING_SQ_CQ_OVERFLOW;
        }

        io_commit_cqring(ctx);
        spin_unlock_irqrestore(&ctx->completion_lock, flags);
        io_cqring_ev_posted(ctx);

        while (!list_empty(&list)) {
                req = list_first_entry(&list, struct io_kiocb, compl.list);
                list_del(&req->compl.list);
                io_put_req(req);
        }

        return all_flushed;
}

static void io_cqring_overflow_flush(struct io_ring_ctx *ctx, bool force,
                                     struct task_struct *tsk,
                                     struct files_struct *files)
{
        if (test_bit(0, &ctx->cq_check_overflow)) {
                /* iopoll syncs against uring_lock, not completion_lock */
                if (ctx->flags & IORING_SETUP_IOPOLL)
                        mutex_lock(&ctx->uring_lock);
                __io_cqring_overflow_flush(ctx, force, tsk, files);
                if (ctx->flags & IORING_SETUP_IOPOLL)
                        mutex_unlock(&ctx->uring_lock);
        }
}

static void __io_cqring_fill_event(struct io_kiocb *req, long res, long cflags)
{
        struct io_ring_ctx *ctx = req->ctx;
        struct io_uring_cqe *cqe;

        trace_io_uring_complete(ctx, req->user_data, res);

        /*
         * If we can't get a cq entry, userspace overflowed the
         * submission (by quite a lot). Increment the overflow count in
         * the ring.
         */
        cqe = io_get_cqring(ctx);
        if (likely(cqe)) {
                WRITE_ONCE(cqe->user_data, req->user_data);
                WRITE_ONCE(cqe->res, res);
                WRITE_ONCE(cqe->flags, cflags);
        } else if (ctx->cq_overflow_flushed ||
                   atomic_read(&req->task->io_uring->in_idle)) {
                /*
                 * If we're in ring overflow flush mode, or in task cancel mode,
                 * then we cannot store the request for later flushing, we need
                 * to drop it on the floor.
                 */
                ctx->cached_cq_overflow++;
                WRITE_ONCE(ctx->rings->cq_overflow, ctx->cached_cq_overflow);
        } else {
                if (list_empty(&ctx->cq_overflow_list)) {
                        set_bit(0, &ctx->sq_check_overflow);
                        set_bit(0, &ctx->cq_check_overflow);
                        ctx->rings->sq_flags |= IORING_SQ_CQ_OVERFLOW;
                }
                io_clean_op(req);
                req->result = res;
                req->compl.cflags = cflags;
                refcount_inc(&req->refs);
                list_add_tail(&req->compl.list, &ctx->cq_overflow_list);
        }
}

static void io_cqring_fill_event(struct io_kiocb *req, long res)
{
        __io_cqring_fill_event(req, res, 0);
}

static void io_cqring_add_event(struct io_kiocb *req, long res, long cflags)
{
        struct io_ring_ctx *ctx = req->ctx;
        unsigned long flags;

        spin_lock_irqsave(&ctx->completion_lock, flags);
        __io_cqring_fill_event(req, res, cflags);
        io_commit_cqring(ctx);
        spin_unlock_irqrestore(&ctx->completion_lock, flags);

        io_cqring_ev_posted(ctx);
}

static void io_submit_flush_completions(struct io_comp_state *cs)
{
        struct io_ring_ctx *ctx = cs->ctx;

        spin_lock_irq(&ctx->completion_lock);
        while (!list_empty(&cs->list)) {
                struct io_kiocb *req;

                req = list_first_entry(&cs->list, struct io_kiocb, compl.list);
                list_del(&req->compl.list);
                __io_cqring_fill_event(req, req->result, req->compl.cflags);

                /*
                 * io_free_req() doesn't care about completion_lock unless one
                 * of these flags is set. REQ_F_WORK_INITIALIZED is in the list
                 * because of a potential deadlock with req->work.fs->lock
                 */
                if (req->flags & (REQ_F_FAIL_LINK|REQ_F_LINK_TIMEOUT
                                 |REQ_F_WORK_INITIALIZED)) {
                        spin_unlock_irq(&ctx->completion_lock);
                        io_put_req(req);
                        spin_lock_irq(&ctx->completion_lock);
                } else {
                        io_put_req(req);
                }
        }
        io_commit_cqring(ctx);
        spin_unlock_irq(&ctx->completion_lock);

        io_cqring_ev_posted(ctx);
        cs->nr = 0;
}

static void __io_req_complete(struct io_kiocb *req, long res, unsigned cflags,
                              struct io_comp_state *cs)
{
        if (!cs) {
                io_cqring_add_event(req, res, cflags);
                io_put_req(req);
        } else {
                io_clean_op(req);
                req->result = res;
                req->compl.cflags = cflags;
                list_add_tail(&req->compl.list, &cs->list);
                if (++cs->nr >= 32)
                        io_submit_flush_completions(cs);
        }
}

static void io_req_complete(struct io_kiocb *req, long res)
{
        __io_req_complete(req, res, 0, NULL);
}

static inline bool io_is_fallback_req(struct io_kiocb *req)
{
        return req == (struct io_kiocb *)
                        ((unsigned long) req->ctx->fallback_req & ~1UL);
}

static struct io_kiocb *io_get_fallback_req(struct io_ring_ctx *ctx)
{
        struct io_kiocb *req;

        req = ctx->fallback_req;
        if (!test_and_set_bit_lock(0, (unsigned long *) &ctx->fallback_req))
                return req;

        return NULL;
}

static struct io_kiocb *io_alloc_req(struct io_ring_ctx *ctx,
                                     struct io_submit_state *state)
{
        if (!state->free_reqs) {
                gfp_t gfp = GFP_KERNEL | __GFP_NOWARN;
                size_t sz;
                int ret;

                sz = min_t(size_t, state->ios_left, ARRAY_SIZE(state->reqs));
                ret = kmem_cache_alloc_bulk(req_cachep, gfp, sz, state->reqs);

                /*
                 * Bulk alloc is all-or-nothing. If we fail to get a batch,
                 * retry single alloc to be on the safe side.
                 */
                if (unlikely(ret <= 0)) {
                        state->reqs[0] = kmem_cache_alloc(req_cachep, gfp);
                        if (!state->reqs[0])
                                goto fallback;
                        ret = 1;
                }
                state->free_reqs = ret;
        }

        state->free_reqs--;
        return state->reqs[state->free_reqs];
fallback:
        return io_get_fallback_req(ctx);
}

static inline void io_put_file(struct io_kiocb *req, struct file *file,
                          bool fixed)
{
        if (!fixed)
                fput(file);
}

static void io_dismantle_req(struct io_kiocb *req)
{
        io_clean_op(req);

        if (req->async_data)
                kfree(req->async_data);
        if (req->file)
                io_put_file(req, req->file, (req->flags & REQ_F_FIXED_FILE));
        if (req->fixed_file_refs)
                percpu_ref_put(req->fixed_file_refs);
        io_req_clean_work(req);
}

static void __io_free_req(struct io_kiocb *req)
{
        struct io_uring_task *tctx = req->task->io_uring;
        struct io_ring_ctx *ctx = req->ctx;

        io_dismantle_req(req);

        percpu_counter_dec(&tctx->inflight);
        if (atomic_read(&tctx->in_idle))
                wake_up(&tctx->wait);
        put_task_struct(req->task);

        if (likely(!io_is_fallback_req(req)))
                kmem_cache_free(req_cachep, req);
        else
                clear_bit_unlock(0, (unsigned long *) &ctx->fallback_req);
        percpu_ref_put(&ctx->refs);
}

static inline void io_remove_next_linked(struct io_kiocb *req)
{
        struct io_kiocb *nxt = req->link;

        req->link = nxt->link;
        nxt->link = NULL;
}

static void io_kill_linked_timeout(struct io_kiocb *req)
{
        struct io_ring_ctx *ctx = req->ctx;
        struct io_kiocb *link;
        bool cancelled = false;
        unsigned long flags;

        spin_lock_irqsave(&ctx->completion_lock, flags);
        link = req->link;

        /*
         * Can happen if a linked timeout fired and link had been like
         * req -> link t-out -> link t-out [-> ...]
         */
        if (link && (link->flags & REQ_F_LTIMEOUT_ACTIVE)) {
                struct io_timeout_data *io = link->async_data;
                int ret;

                io_remove_next_linked(req);
                link->timeout.head = NULL;
                ret = hrtimer_try_to_cancel(&io->timer);
                if (ret != -1) {
                        io_cqring_fill_event(link, -ECANCELED);
                        io_commit_cqring(ctx);
                        cancelled = true;
                }
        }
        req->flags &= ~REQ_F_LINK_TIMEOUT;
        spin_unlock_irqrestore(&ctx->completion_lock, flags);

        if (cancelled) {
                io_cqring_ev_posted(ctx);
                io_put_req(link);
        }
}


static void io_fail_links(struct io_kiocb *req)
{
        struct io_kiocb *link, *nxt;
        struct io_ring_ctx *ctx = req->ctx;
        unsigned long flags;

        spin_lock_irqsave(&ctx->completion_lock, flags);
        link = req->link;
        req->link = NULL;

        while (link) {
                nxt = link->link;
                link->link = NULL;

                trace_io_uring_fail_link(req, link);
                io_cqring_fill_event(link, -ECANCELED);

                /*
                 * It's ok to free under spinlock as they're not linked anymore,
                 * but avoid REQ_F_WORK_INITIALIZED because it may deadlock on
                 * work.fs->lock.
                 */
                if (link->flags & REQ_F_WORK_INITIALIZED)
                        io_put_req_deferred(link, 2);
                else
                        io_double_put_req(link);
                link = nxt;
        }
        io_commit_cqring(ctx);
        spin_unlock_irqrestore(&ctx->completion_lock, flags);

        io_cqring_ev_posted(ctx);
}

static struct io_kiocb *__io_req_find_next(struct io_kiocb *req)
{
        if (req->flags & REQ_F_LINK_TIMEOUT)
                io_kill_linked_timeout(req);

        /*
         * If LINK is set, we have dependent requests in this chain. If we
         * didn't fail this request, queue the first one up, moving any other
         * dependencies to the next request. In case of failure, fail the rest
         * of the chain.
         */
        if (likely(!(req->flags & REQ_F_FAIL_LINK))) {
                struct io_kiocb *nxt = req->link;

                req->link = NULL;
                return nxt;
        }
        io_fail_links(req);
        return NULL;
}

static inline struct io_kiocb *io_req_find_next(struct io_kiocb *req)
{
        if (likely(!(req->link) && !(req->flags & REQ_F_LINK_TIMEOUT)))
                return NULL;
        return __io_req_find_next(req);
}

static int io_req_task_work_add(struct io_kiocb *req)
{
        struct task_struct *tsk = req->task;
        struct io_ring_ctx *ctx = req->ctx;
        enum task_work_notify_mode notify;
        int ret;

        if (tsk->flags & PF_EXITING)
                return -ESRCH;

        /*
         * SQPOLL kernel thread doesn't need notification, just a wakeup. For
         * all other cases, use TWA_SIGNAL unconditionally to ensure we're
         * processing task_work. There's no reliable way to tell if TWA_RESUME
         * will do the job.
         */
        notify = TWA_NONE;
        if (!(ctx->flags & IORING_SETUP_SQPOLL))
                notify = TWA_SIGNAL;

        ret = task_work_add(tsk, &req->task_work, notify);
        if (!ret)
                wake_up_process(tsk);

        return ret;
}

static void __io_req_task_cancel(struct io_kiocb *req, int error)
{
        struct io_ring_ctx *ctx = req->ctx;

        spin_lock_irq(&ctx->completion_lock);
        io_cqring_fill_event(req, error);
        io_commit_cqring(ctx);
        spin_unlock_irq(&ctx->completion_lock);

        io_cqring_ev_posted(ctx);
        req_set_fail_links(req);
        io_double_put_req(req);
}

static void io_req_task_cancel(struct callback_head *cb)
{
        struct io_kiocb *req = container_of(cb, struct io_kiocb, task_work);
        struct io_ring_ctx *ctx = req->ctx;

        __io_req_task_cancel(req, -ECANCELED);
        percpu_ref_put(&ctx->refs);
}

static void __io_req_task_submit(struct io_kiocb *req)
{
        struct io_ring_ctx *ctx = req->ctx;
        bool fail;

        fail = __io_sq_thread_acquire_mm(ctx) ||
                __io_sq_thread_acquire_files(ctx);
        mutex_lock(&ctx->uring_lock);
        if (!fail)
                __io_queue_sqe(req, NULL);
        else
                __io_req_task_cancel(req, -EFAULT);
        mutex_unlock(&ctx->uring_lock);
}

static void io_req_task_submit(struct callback_head *cb)
{
        struct io_kiocb *req = container_of(cb, struct io_kiocb, task_work);
        struct io_ring_ctx *ctx = req->ctx;

        __io_req_task_submit(req);
        percpu_ref_put(&ctx->refs);
}

static void io_req_task_queue(struct io_kiocb *req)
{
        int ret;

        init_task_work(&req->task_work, io_req_task_submit);
        percpu_ref_get(&req->ctx->refs);

        ret = io_req_task_work_add(req);
        if (unlikely(ret)) {
                struct task_struct *tsk;

                init_task_work(&req->task_work, io_req_task_cancel);
                tsk = io_wq_get_task(req->ctx->io_wq);
                task_work_add(tsk, &req->task_work, TWA_NONE);
                wake_up_process(tsk);
        }
}

static inline void io_queue_next(struct io_kiocb *req)
{
        struct io_kiocb *nxt = io_req_find_next(req);

        if (nxt)
                io_req_task_queue(nxt);
}

static void io_free_req(struct io_kiocb *req)
{
        io_queue_next(req);
        __io_free_req(req);
}

struct req_batch {
        void *reqs[IO_IOPOLL_BATCH];
        int to_free;

        struct task_struct      *task;
        int                     task_refs;
};

static inline void io_init_req_batch(struct req_batch *rb)
{
        rb->to_free = 0;
        rb->task_refs = 0;
        rb->task = NULL;
}

static void __io_req_free_batch_flush(struct io_ring_ctx *ctx,
                                      struct req_batch *rb)
{
        kmem_cache_free_bulk(req_cachep, rb->to_free, rb->reqs);
        percpu_ref_put_many(&ctx->refs, rb->to_free);
        rb->to_free = 0;
}

static void io_req_free_batch_finish(struct io_ring_ctx *ctx,
                                     struct req_batch *rb)
{
        if (rb->to_free)
                __io_req_free_batch_flush(ctx, rb);
        if (rb->task) {
                struct io_uring_task *tctx = rb->task->io_uring;

                percpu_counter_sub(&tctx->inflight, rb->task_refs);
                put_task_struct_many(rb->task, rb->task_refs);
                rb->task = NULL;
        }
}

static void io_req_free_batch(struct req_batch *rb, struct io_kiocb *req)
{
        if (unlikely(io_is_fallback_req(req))) {
                io_free_req(req);
                return;
        }
        io_queue_next(req);

        if (req->task != rb->task) {
                if (rb->task) {
                        struct io_uring_task *tctx = rb->task->io_uring;

                        percpu_counter_sub(&tctx->inflight, rb->task_refs);
                        put_task_struct_many(rb->task, rb->task_refs);
                }
                rb->task = req->task;
                rb->task_refs = 0;
        }
        rb->task_refs++;

        io_dismantle_req(req);
        rb->reqs[rb->to_free++] = req;
        if (unlikely(rb->to_free == ARRAY_SIZE(rb->reqs)))
                __io_req_free_batch_flush(req->ctx, rb);
}

/*
 * Drop reference to request, return next in chain (if there is one) if this
 * was the last reference to this request.
 */
static struct io_kiocb *io_put_req_find_next(struct io_kiocb *req)
{
        struct io_kiocb *nxt = NULL;

        if (refcount_dec_and_test(&req->refs)) {
                nxt = io_req_find_next(req);
                __io_free_req(req);
        }
        return nxt;
}

static void io_put_req(struct io_kiocb *req)
{
        if (refcount_dec_and_test(&req->refs))
                io_free_req(req);
}

static void io_put_req_deferred_cb(struct callback_head *cb)
{
        struct io_kiocb *req = container_of(cb, struct io_kiocb, task_work);

        io_free_req(req);
}

static void io_free_req_deferred(struct io_kiocb *req)
{
        int ret;

        init_task_work(&req->task_work, io_put_req_deferred_cb);
        ret = io_req_task_work_add(req);
        if (unlikely(ret)) {
                struct task_struct *tsk;

                tsk = io_wq_get_task(req->ctx->io_wq);
                task_work_add(tsk, &req->task_work, TWA_NONE);
                wake_up_process(tsk);
        }
}

static inline void io_put_req_deferred(struct io_kiocb *req, int refs)
{
        if (refcount_sub_and_test(refs, &req->refs))
                io_free_req_deferred(req);
}

static struct io_wq_work *io_steal_work(struct io_kiocb *req)
{
        struct io_kiocb *nxt;

        /*
         * A ref is owned by io-wq in which context we're. So, if that's the
         * last one, it's safe to steal next work. False negatives are Ok,
         * it just will be re-punted async in io_put_work()
         */
        if (refcount_read(&req->refs) != 1)
                return NULL;

        nxt = io_req_find_next(req);
        return nxt ? &nxt->work : NULL;
}

static void io_double_put_req(struct io_kiocb *req)
{
        /* drop both submit and complete references */
        if (refcount_sub_and_test(2, &req->refs))
                io_free_req(req);
}

static unsigned io_cqring_events(struct io_ring_ctx *ctx)
{
        /* See comment at the top of this file */
        smp_rmb();
        return __io_cqring_events(ctx);
}

static inline unsigned int io_sqring_entries(struct io_ring_ctx *ctx)
{
        struct io_rings *rings = ctx->rings;

        /* make sure SQ entry isn't read before tail */
        return smp_load_acquire(&rings->sq.tail) - ctx->cached_sq_head;
}

static unsigned int io_put_kbuf(struct io_kiocb *req, struct io_buffer *kbuf)
{
        unsigned int cflags;

        cflags = kbuf->bid << IORING_CQE_BUFFER_SHIFT;
        cflags |= IORING_CQE_F_BUFFER;
        req->flags &= ~REQ_F_BUFFER_SELECTED;
        kfree(kbuf);
        return cflags;
}

static inline unsigned int io_put_rw_kbuf(struct io_kiocb *req)
{
        struct io_buffer *kbuf;

        kbuf = (struct io_buffer *) (unsigned long) req->rw.addr;
        return io_put_kbuf(req, kbuf);
}

static inline bool io_run_task_work(void)
{
        /*
         * Not safe to run on exiting task, and the task_work handling will
         * not add work to such a task.
         */
        if (unlikely(current->flags & PF_EXITING))
                return false;
        if (current->task_works) {
                __set_current_state(TASK_RUNNING);
                task_work_run();
                return true;
        }

        return false;
}

static void io_iopoll_queue(struct list_head *again)
{
        struct io_kiocb *req;

        do {
                req = list_first_entry(again, struct io_kiocb, inflight_entry);
                list_del(&req->inflight_entry);
                __io_complete_rw(req, -EAGAIN, 0, NULL);
        } while (!list_empty(again));
}

/*
 * Find and free completed poll iocbs
 */
static void io_iopoll_complete(struct io_ring_ctx *ctx, unsigned int *nr_events,
                               struct list_head *done)
{
        struct req_batch rb;
        struct io_kiocb *req;
        LIST_HEAD(again);

        /* order with ->result store in io_complete_rw_iopoll() */
        smp_rmb();

        io_init_req_batch(&rb);
        while (!list_empty(done)) {
                int cflags = 0;

                req = list_first_entry(done, struct io_kiocb, inflight_entry);
                if (READ_ONCE(req->result) == -EAGAIN) {
                        req->result = 0;
                        req->iopoll_completed = 0;
                        list_move_tail(&req->inflight_entry, &again);
                        continue;
                }
                list_del(&req->inflight_entry);

                if (req->flags & REQ_F_BUFFER_SELECTED)
                        cflags = io_put_rw_kbuf(req);

                __io_cqring_fill_event(req, req->result, cflags);
                (*nr_events)++;

                if (refcount_dec_and_test(&req->refs))
                        io_req_free_batch(&rb, req);
        }

        io_commit_cqring(ctx);
        io_cqring_ev_posted_iopoll(ctx);
        io_req_free_batch_finish(ctx, &rb);

        if (!list_empty(&again))
                io_iopoll_queue(&again);
}

static int io_do_iopoll(struct io_ring_ctx *ctx, unsigned int *nr_events,
                        long min)
{
        struct io_kiocb *req, *tmp;
        LIST_HEAD(done);
        bool spin;
        int ret;

        /*
         * Only spin for completions if we don't have multiple devices hanging
         * off our complete list, and we're under the requested amount.
         */
        spin = !ctx->poll_multi_file && *nr_events < min;

        ret = 0;
        list_for_each_entry_safe(req, tmp, &ctx->iopoll_list, inflight_entry) {
                struct kiocb *kiocb = &req->rw.kiocb;

                /*
                 * Move completed and retryable entries to our local lists.
                 * If we find a request that requires polling, break out
                 * and complete those lists first, if we have entries there.
                 */
                if (READ_ONCE(req->iopoll_completed)) {
                        list_move_tail(&req->inflight_entry, &done);
                        continue;
                }
                if (!list_empty(&done))
                        break;

                ret = kiocb->ki_filp->f_op->iopoll(kiocb, spin);
                if (ret < 0)
                        break;

                /* iopoll may have completed current req */
                if (READ_ONCE(req->iopoll_completed))
                        list_move_tail(&req->inflight_entry, &done);

                if (ret && spin)
                        spin = false;
                ret = 0;
        }

        if (!list_empty(&done))
                io_iopoll_complete(ctx, nr_events, &done);

        return ret;
}

/*
 * Poll for a minimum of 'min' events. Note that if min == 0 we consider that a
 * non-spinning poll check - we'll still enter the driver poll loop, but only
 * as a non-spinning completion check.
 */
static int io_iopoll_getevents(struct io_ring_ctx *ctx, unsigned int *nr_events,
                                long min)
{
        while (!list_empty(&ctx->iopoll_list) && !need_resched()) {
                int ret;

                ret = io_do_iopoll(ctx, nr_events, min);
                if (ret < 0)
                        return ret;
                if (*nr_events >= min)
                        return 0;
        }

        return 1;
}

/*
 * We can't just wait for polled events to come to us, we have to actively
 * find and complete them.
 */
static void io_iopoll_try_reap_events(struct io_ring_ctx *ctx)
{
        if (!(ctx->flags & IORING_SETUP_IOPOLL))
                return;

        mutex_lock(&ctx->uring_lock);
        while (!list_empty(&ctx->iopoll_list)) {
                unsigned int nr_events = 0;

                io_do_iopoll(ctx, &nr_events, 0);

                /* let it sleep and repeat later if can't complete a request */
                if (nr_events == 0)
                        break;
                /*
                 * Ensure we allow local-to-the-cpu processing to take place,
                 * in this case we need to ensure that we reap all events.
                 * Also let task_work, etc. to progress by releasing the mutex
                 */
                if (need_resched()) {
                        mutex_unlock(&ctx->uring_lock);
                        cond_resched();
                        mutex_lock(&ctx->uring_lock);
                }
        }
        mutex_unlock(&ctx->uring_lock);
}

static int io_iopoll_check(struct io_ring_ctx *ctx, long min)
{
        unsigned int nr_events = 0;
        int iters = 0, ret = 0;

        /*
         * We disallow the app entering submit/complete with polling, but we
         * still need to lock the ring to prevent racing with polled issue
         * that got punted to a workqueue.
         */
        mutex_lock(&ctx->uring_lock);
        do {
                /*
                 * Don't enter poll loop if we already have events pending.
                 * If we do, we can potentially be spinning for commands that
                 * already triggered a CQE (eg in error).
                 */
                if (test_bit(0, &ctx->cq_check_overflow))
                        __io_cqring_overflow_flush(ctx, false, NULL, NULL);
                if (io_cqring_events(ctx))
                        break;

                /*
                 * If a submit got punted to a workqueue, we can have the
                 * application entering polling for a command before it gets
                 * issued. That app will hold the uring_lock for the duration
                 * of the poll right here, so we need to take a breather every
                 * now and then to ensure that the issue has a chance to add
                 * the poll to the issued list. Otherwise we can spin here
                 * forever, while the workqueue is stuck trying to acquire the
                 * very same mutex.
                 */
                if (!(++iters & 7)) {
                        mutex_unlock(&ctx->uring_lock);
                        io_run_task_work();
                        mutex_lock(&ctx->uring_lock);
                }

                ret = io_iopoll_getevents(ctx, &nr_events, min);
                if (ret <= 0)
                        break;
                ret = 0;
        } while (min && !nr_events && !need_resched());

        mutex_unlock(&ctx->uring_lock);
        return ret;
}

static void kiocb_end_write(struct io_kiocb *req)
{
        /*
         * Tell lockdep we inherited freeze protection from submission
         * thread.
         */
        if (req->flags & REQ_F_ISREG) {
                struct inode *inode = file_inode(req->file);

                __sb_writers_acquired(inode->i_sb, SB_FREEZE_WRITE);
        }
        file_end_write(req->file);
}

static void io_complete_rw_common(struct kiocb *kiocb, long res,
                                  struct io_comp_state *cs)
{
        struct io_kiocb *req = container_of(kiocb, struct io_kiocb, rw.kiocb);
        int cflags = 0;

        if (kiocb->ki_flags & IOCB_WRITE)
                kiocb_end_write(req);

        if (res != req->result)
                req_set_fail_links(req);
        if (req->flags & REQ_F_BUFFER_SELECTED)
                cflags = io_put_rw_kbuf(req);
        __io_req_complete(req, res, cflags, cs);
}

#ifdef CONFIG_BLOCK
static bool io_resubmit_prep(struct io_kiocb *req, int error)
{
        struct iovec inline_vecs[UIO_FASTIOV], *iovec = inline_vecs;
        ssize_t ret = -ECANCELED;
        struct iov_iter iter;
        int rw;

        if (error) {
                ret = error;
                goto end_req;
        }

        switch (req->opcode) {
        case IORING_OP_READV:
        case IORING_OP_READ_FIXED:
        case IORING_OP_READ:
                rw = READ;
                break;
        case IORING_OP_WRITEV:
        case IORING_OP_WRITE_FIXED:
        case IORING_OP_WRITE:
                rw = WRITE;
                break;
        default:
                printk_once(KERN_WARNING "io_uring: bad opcode in resubmit %d\n",
                                req->opcode);
                goto end_req;
        }

        if (!req->async_data) {
                ret = io_import_iovec(rw, req, &iovec, &iter, false);
                if (ret < 0)
                        goto end_req;
                ret = io_setup_async_rw(req, iovec, inline_vecs, &iter, false);
                if (!ret)
                        return true;
                kfree(iovec);
        } else {
                return true;
        }
end_req:
        req_set_fail_links(req);
        return false;
}
#endif

static bool io_rw_reissue(struct io_kiocb *req, long res)
{
#ifdef CONFIG_BLOCK
        umode_t mode = file_inode(req->file)->i_mode;
        int ret;

        if (!S_ISBLK(mode) && !S_ISREG(mode))
                return false;
        if ((res != -EAGAIN && res != -EOPNOTSUPP) || io_wq_current_is_worker())
                return false;

        ret = io_sq_thread_acquire_mm_files(req->ctx, req);

        if (io_resubmit_prep(req, ret)) {
                refcount_inc(&req->refs);
                io_queue_async_work(req);
                return true;
        }

#endif
        return false;
}

static void __io_complete_rw(struct io_kiocb *req, long res, long res2,
                             struct io_comp_state *cs)
{
        if (!io_rw_reissue(req, res))
                io_complete_rw_common(&req->rw.kiocb, res, cs);
}

static void io_complete_rw(struct kiocb *kiocb, long res, long res2)
{
        struct io_kiocb *req = container_of(kiocb, struct io_kiocb, rw.kiocb);

        __io_complete_rw(req, res, res2, NULL);
}

static void io_complete_rw_iopoll(struct kiocb *kiocb, long res, long res2)
{
        struct io_kiocb *req = container_of(kiocb, struct io_kiocb, rw.kiocb);

        if (kiocb->ki_flags & IOCB_WRITE)
                kiocb_end_write(req);

        if (res != -EAGAIN && res != req->result)
                req_set_fail_links(req);

        WRITE_ONCE(req->result, res);
        /* order with io_poll_complete() checking ->result */
        smp_wmb();
        WRITE_ONCE(req->iopoll_completed, 1);
}

/*
 * After the iocb has been issued, it's safe to be found on the poll list.
 * Adding the kiocb to the list AFTER submission ensures that we don't
 * find it from a io_iopoll_getevents() thread before the issuer is done
 * accessing the kiocb cookie.
 */
static void io_iopoll_req_issued(struct io_kiocb *req, bool in_async)
{
        struct io_ring_ctx *ctx = req->ctx;

        /*
         * Track whether we have multiple files in our lists. This will impact
         * how we do polling eventually, not spinning if we're on potentially
         * different devices.
         */
        if (list_empty(&ctx->iopoll_list)) {
                ctx->poll_multi_file = false;
        } else if (!ctx->poll_multi_file) {
                struct io_kiocb *list_req;

                list_req = list_first_entry(&ctx->iopoll_list, struct io_kiocb,
                                                inflight_entry);
                if (list_req->file != req->file)
                        ctx->poll_multi_file = true;
        }

        /*
         * For fast devices, IO may have already completed. If it has, add
         * it to the front so we find it first.
         */
        if (READ_ONCE(req->iopoll_completed))
                list_add(&req->inflight_entry, &ctx->iopoll_list);
        else
                list_add_tail(&req->inflight_entry, &ctx->iopoll_list);

        /*
         * If IORING_SETUP_SQPOLL is enabled, sqes are either handled in sq thread
         * task context or in io worker task context. If current task context is
         * sq thread, we don't need to check whether should wake up sq thread.
         */
        if (in_async && (ctx->flags & IORING_SETUP_SQPOLL) &&
            wq_has_sleeper(&ctx->sq_data->wait))
                wake_up(&ctx->sq_data->wait);
}

static inline void __io_state_file_put(struct io_submit_state *state)
{
        fput_many(state->file, state->file_refs);
        state->file_refs = 0;
}

static inline void io_state_file_put(struct io_submit_state *state)
{
        if (state->file_refs)
                __io_state_file_put(state);
}

/*
 * Get as many references to a file as we have IOs left in this submission,
 * assuming most submissions are for one file, or at least that each file
 * has more than one submission.
 */
static struct file *__io_file_get(struct io_submit_state *state, int fd)
{
        if (!state)
                return fget(fd);

        if (state->file_refs) {
                if (state->fd == fd) {
                        state->file_refs--;
                        return state->file;
                }
                __io_state_file_put(state);
        }
        state->file = fget_many(fd, state->ios_left);
        if (unlikely(!state->file))
                return NULL;

        state->fd = fd;
        state->file_refs = state->ios_left - 1;
        return state->file;
}

static bool io_bdev_nowait(struct block_device *bdev)
{
        return !bdev || blk_queue_nowait(bdev_get_queue(bdev));
}

/*
 * If we tracked the file through the SCM inflight mechanism, we could support
 * any file. For now, just ensure that anything potentially problematic is done
 * inline.
 */
static bool io_file_supports_async(struct file *file, int rw)
{
        umode_t mode = file_inode(file)->i_mode;

        if (S_ISBLK(mode)) {
                if (IS_ENABLED(CONFIG_BLOCK) &&
                    io_bdev_nowait(I_BDEV(file->f_mapping->host)))
                        return true;
                return false;
        }
        if (S_ISCHR(mode) || S_ISSOCK(mode))
                return true;
        if (S_ISREG(mode)) {
                if (IS_ENABLED(CONFIG_BLOCK) &&
                    io_bdev_nowait(file->f_inode->i_sb->s_bdev) &&
                    file->f_op != &io_uring_fops)
                        return true;
                return false;
        }

        /* any ->read/write should understand O_NONBLOCK */
        if (file->f_flags & O_NONBLOCK)
                return true;

        if (!(file->f_mode & FMODE_NOWAIT))
                return false;

        if (rw == READ)
                return file->f_op->read_iter != NULL;

        return file->f_op->write_iter != NULL;
}

static int io_prep_rw(struct io_kiocb *req, const struct io_uring_sqe *sqe)
{
        struct io_ring_ctx *ctx = req->ctx;
        struct kiocb *kiocb = &req->rw.kiocb;
        unsigned ioprio;
        int ret;

        if (S_ISREG(file_inode(req->file)->i_mode))
                req->flags |= REQ_F_ISREG;

        kiocb->ki_pos = READ_ONCE(sqe->off);
        if (kiocb->ki_pos == -1 && !(req->file->f_mode & FMODE_STREAM)) {
                req->flags |= REQ_F_CUR_POS;
                kiocb->ki_pos = req->file->f_pos;
        }
        kiocb->ki_hint = ki_hint_validate(file_write_hint(kiocb->ki_filp));
        kiocb->ki_flags = iocb_flags(kiocb->ki_filp);
        ret = kiocb_set_rw_flags(kiocb, READ_ONCE(sqe->rw_flags));
        if (unlikely(ret))
                return ret;

        ioprio = READ_ONCE(sqe->ioprio);
        if (ioprio) {
                ret = ioprio_check_cap(ioprio);
                if (ret)
                        return ret;

                kiocb->ki_ioprio = ioprio;
        } else
                kiocb->ki_ioprio = get_current_ioprio();

        /* don't allow async punt if RWF_NOWAIT was requested */
        if (kiocb->ki_flags & IOCB_NOWAIT)
                req->flags |= REQ_F_NOWAIT;

        if (ctx->flags & IORING_SETUP_IOPOLL) {
                if (!(kiocb->ki_flags & IOCB_DIRECT) ||
                    !kiocb->ki_filp->f_op->iopoll)
                        return -EOPNOTSUPP;

                kiocb->ki_flags |= IOCB_HIPRI;
                kiocb->ki_complete = io_complete_rw_iopoll;
                req->iopoll_completed = 0;
        } else {
                if (kiocb->ki_flags & IOCB_HIPRI)
                        return -EINVAL;
                kiocb->ki_complete = io_complete_rw;
        }

        req->rw.addr = READ_ONCE(sqe->addr);
        req->rw.len = READ_ONCE(sqe->len);
        req->buf_index = READ_ONCE(sqe->buf_index);
        return 0;
}

static inline void io_rw_done(struct kiocb *kiocb, ssize_t ret)
{
        switch (ret) {
        case -EIOCBQUEUED:
                break;
        case -ERESTARTSYS:
        case -ERESTARTNOINTR:
        case -ERESTARTNOHAND:
        case -ERESTART_RESTARTBLOCK:
                /*
                 * We can't just restart the syscall, since previously
                 * submitted sqes may already be in progress. Just fail this
                 * IO with EINTR.
                 */
                ret = -EINTR;
                fallthrough;
        default:
                kiocb->ki_complete(kiocb, ret, 0);
        }
}

static void kiocb_done(struct kiocb *kiocb, ssize_t ret,
                       struct io_comp_state *cs)
{
        struct io_kiocb *req = container_of(kiocb, struct io_kiocb, rw.kiocb);
        struct io_async_rw *io = req->async_data;

        /* add previously done IO, if any */
        if (io && io->bytes_done > 0) {
                if (ret < 0)
                        ret = io->bytes_done;
                else
                        ret += io->bytes_done;
        }

        if (req->flags & REQ_F_CUR_POS)
                req->file->f_pos = kiocb->ki_pos;
        if (ret >= 0 && kiocb->ki_complete == io_complete_rw)
                __io_complete_rw(req, ret, 0, cs);
        else
                io_rw_done(kiocb, ret);
}

static ssize_t io_import_fixed(struct io_kiocb *req, int rw,
                               struct iov_iter *iter)
{
        struct io_ring_ctx *ctx = req->ctx;
        size_t len = req->rw.len;
        struct io_mapped_ubuf *imu;
        u16 index, buf_index = req->buf_index;
        size_t offset;
        u64 buf_addr;

        if (unlikely(buf_index >= ctx->nr_user_bufs))
                return -EFAULT;
        index = array_index_nospec(buf_index, ctx->nr_user_bufs);
        imu = &ctx->user_bufs[index];
        buf_addr = req->rw.addr;

        /* overflow */
        if (buf_addr + len < buf_addr)
                return -EFAULT;
        /* not inside the mapped region */
        if (buf_addr < imu->ubuf || buf_addr + len > imu->ubuf + imu->len)
                return -EFAULT;

        /*
         * May not be a start of buffer, set size appropriately
         * and advance us to the beginning.
         */
        offset = buf_addr - imu->ubuf;
        iov_iter_bvec(iter, rw, imu->bvec, imu->nr_bvecs, offset + len);

        if (offset) {
                /*
                 * Don't use iov_iter_advance() here, as it's really slow for
                 * using the latter parts of a big fixed buffer - it iterates
                 * over each segment manually. We can cheat a bit here, because
                 * we know that:
                 *
                 * 1) it's a BVEC iter, we set it up
                 * 2) all bvecs are PAGE_SIZE in size, except potentially the
                 *    first and last bvec
                 *
                 * So just find our index, and adjust the iterator afterwards.
                 * If the offset is within the first bvec (or the whole first
                 * bvec, just use iov_iter_advance(). This makes it easier
                 * since we can just skip the first segment, which may not
                 * be PAGE_SIZE aligned.
                 */
                const struct bio_vec *bvec = imu->bvec;

                if (offset <= bvec->bv_len) {
                        iov_iter_advance(iter, offset);
                } else {
                        unsigned long seg_skip;

                        /* skip first vec */
                        offset -= bvec->bv_len;
                        seg_skip = 1 + (offset >> PAGE_SHIFT);

                        iter->bvec = bvec + seg_skip;
                        iter->nr_segs -= seg_skip;
                        iter->count -= bvec->bv_len + offset;
                        iter->iov_offset = offset & ~PAGE_MASK;
                }
        }

        return len;
}

static void io_ring_submit_unlock(struct io_ring_ctx *ctx, bool needs_lock)
{
        if (needs_lock)
                mutex_unlock(&ctx->uring_lock);
}

static void io_ring_submit_lock(struct io_ring_ctx *ctx, bool needs_lock)
{
        /*
         * "Normal" inline submissions always hold the uring_lock, since we
         * grab it from the system call. Same is true for the SQPOLL offload.
         * The only exception is when we've detached the request and issue it
         * from an async worker thread, grab the lock for that case.
         */
        if (needs_lock)
                mutex_lock(&ctx->uring_lock);
}

static struct io_buffer *io_buffer_select(struct io_kiocb *req, size_t *len,
                                          int bgid, struct io_buffer *kbuf,
                                          bool needs_lock)
{
        struct io_buffer *head;

        if (req->flags & REQ_F_BUFFER_SELECTED)
                return kbuf;

        io_ring_submit_lock(req->ctx, needs_lock);

        lockdep_assert_held(&req->ctx->uring_lock);

        head = idr_find(&req->ctx->io_buffer_idr, bgid);
        if (head) {
                if (!list_empty(&head->list)) {
                        kbuf = list_last_entry(&head->list, struct io_buffer,
                                                        list);
                        list_del(&kbuf->list);
                } else {
                        kbuf = head;
                        idr_remove(&req->ctx->io_buffer_idr, bgid);
                }
                if (*len > kbuf->len)
                        *len = kbuf->len;
        } else {
                kbuf = ERR_PTR(-ENOBUFS);
        }

        io_ring_submit_unlock(req->ctx, needs_lock);

        return kbuf;
}

static void __user *io_rw_buffer_select(struct io_kiocb *req, size_t *len,
                                        bool needs_lock)
{
        struct io_buffer *kbuf;
        u16 bgid;

        kbuf = (struct io_buffer *) (unsigned long) req->rw.addr;
        bgid = req->buf_index;
        kbuf = io_buffer_select(req, len, bgid, kbuf, needs_lock);
        if (IS_ERR(kbuf))
                return kbuf;
        req->rw.addr = (u64) (unsigned long) kbuf;
        req->flags |= REQ_F_BUFFER_SELECTED;
        return u64_to_user_ptr(kbuf->addr);
}

#ifdef CONFIG_COMPAT
static ssize_t io_compat_import(struct io_kiocb *req, struct iovec *iov,
                                bool needs_lock)
{
        struct compat_iovec __user *uiov;
        compat_ssize_t clen;
        void __user *buf;
        ssize_t len;

        uiov = u64_to_user_ptr(req->rw.addr);
        if (!access_ok(uiov, sizeof(*uiov)))
                return -EFAULT;
        if (__get_user(clen, &uiov->iov_len))
                return -EFAULT;
        if (clen < 0)
                return -EINVAL;

        len = clen;
        buf = io_rw_buffer_select(req, &len, needs_lock);
        if (IS_ERR(buf))
                return PTR_ERR(buf);
        iov[0].iov_base = buf;
        iov[0].iov_len = (compat_size_t) len;
        return 0;
}
#endif

static ssize_t __io_iov_buffer_select(struct io_kiocb *req, struct iovec *iov,
                                      bool needs_lock)
{
        struct iovec __user *uiov = u64_to_user_ptr(req->rw.addr);
        void __user *buf;
        ssize_t len;

        if (copy_from_user(iov, uiov, sizeof(*uiov)))
                return -EFAULT;

        len = iov[0].iov_len;
        if (len < 0)
                return -EINVAL;
        buf = io_rw_buffer_select(req, &len, needs_lock);
        if (IS_ERR(buf))
                return PTR_ERR(buf);
        iov[0].iov_base = buf;
        iov[0].iov_len = len;
        return 0;
}

static ssize_t io_iov_buffer_select(struct io_kiocb *req, struct iovec *iov,
                                    bool needs_lock)
{
        if (req->flags & REQ_F_BUFFER_SELECTED) {
                struct io_buffer *kbuf;

                kbuf = (struct io_buffer *) (unsigned long) req->rw.addr;
                iov[0].iov_base = u64_to_user_ptr(kbuf->addr);
                iov[0].iov_len = kbuf->len;
                return 0;
        }
        if (req->rw.len != 1)
                return -EINVAL;

#ifdef CONFIG_COMPAT
        if (req->ctx->compat)
                return io_compat_import(req, iov, needs_lock);
#endif

        return __io_iov_buffer_select(req, iov, needs_lock);
}

static ssize_t io_import_iovec(int rw, struct io_kiocb *req,
                                 struct iovec **iovec, struct iov_iter *iter,
                                 bool needs_lock)
{
        void __user *buf = u64_to_user_ptr(req->rw.addr);
        size_t sqe_len = req->rw.len;
        ssize_t ret;
        u8 opcode;

        opcode = req->opcode;
        if (opcode == IORING_OP_READ_FIXED || opcode == IORING_OP_WRITE_FIXED) {
                *iovec = NULL;
                return io_import_fixed(req, rw, iter);
        }

        /* buffer index only valid with fixed read/write, or buffer select  */
        if (req->buf_index && !(req->flags & REQ_F_BUFFER_SELECT))
                return -EINVAL;

        if (opcode == IORING_OP_READ || opcode == IORING_OP_WRITE) {
                if (req->flags & REQ_F_BUFFER_SELECT) {
                        buf = io_rw_buffer_select(req, &sqe_len, needs_lock);
                        if (IS_ERR(buf))
                                return PTR_ERR(buf);
                        req->rw.len = sqe_len;
                }

                ret = import_single_range(rw, buf, sqe_len, *iovec, iter);
                *iovec = NULL;
                return ret;
        }

        if (req->flags & REQ_F_BUFFER_SELECT) {
                ret = io_iov_buffer_select(req, *iovec, needs_lock);
                if (!ret) {
                        ret = (*iovec)->iov_len;
                        iov_iter_init(iter, rw, *iovec, 1, ret);
                }
                *iovec = NULL;
                return ret;
        }

        return __import_iovec(rw, buf, sqe_len, UIO_FASTIOV, iovec, iter,
                              req->ctx->compat);
}

static inline loff_t *io_kiocb_ppos(struct kiocb *kiocb)
{
        return (kiocb->ki_filp->f_mode & FMODE_STREAM) ? NULL : &kiocb->ki_pos;
}

/*
 * For files that don't have ->read_iter() and ->write_iter(), handle them
 * by looping over ->read() or ->write() manually.
 */
static ssize_t loop_rw_iter(int rw, struct io_kiocb *req, struct iov_iter *iter)
{
        struct kiocb *kiocb = &req->rw.kiocb;
        struct file *file = req->file;
        ssize_t ret = 0;

        /*
         * Don't support polled IO through this interface, and we can't
         * support non-blocking either. For the latter, this just causes
         * the kiocb to be handled from an async context.
         */
        if (kiocb->ki_flags & IOCB_HIPRI)
                return -EOPNOTSUPP;
        if (kiocb->ki_flags & IOCB_NOWAIT)
                return -EAGAIN;

        while (iov_iter_count(iter)) {
                struct iovec iovec;
                ssize_t nr;

                if (!iov_iter_is_bvec(iter)) {
                        iovec = iov_iter_iovec(iter);
                } else {
                        iovec.iov_base = u64_to_user_ptr(req->rw.addr);
                        iovec.iov_len = req->rw.len;
                }

                if (rw == READ) {
                        nr = file->f_op->read(file, iovec.iov_base,
                                              iovec.iov_len, io_kiocb_ppos(kiocb));
                } else {
                        nr = file->f_op->write(file, iovec.iov_base,
                                               iovec.iov_len, io_kiocb_ppos(kiocb));
                }

                if (nr < 0) {
                        if (!ret)
                                ret = nr;
                        break;
                }
                ret += nr;
                if (nr != iovec.iov_len)
                        break;
                req->rw.len -= nr;
                req->rw.addr += nr;
                iov_iter_advance(iter, nr);
        }

        return ret;
}

static void io_req_map_rw(struct io_kiocb *req, const struct iovec *iovec,
                          const struct iovec *fast_iov, struct iov_iter *iter)
{
        struct io_async_rw *rw = req->async_data;

        memcpy(&rw->iter, iter, sizeof(*iter));
        rw->free_iovec = iovec;
        rw->bytes_done = 0;
        /* can only be fixed buffers, no need to do anything */
        if (iov_iter_is_bvec(iter))
                return;
        if (!iovec) {
                unsigned iov_off = 0;

                rw->iter.iov = rw->fast_iov;
                if (iter->iov != fast_iov) {
                        iov_off = iter->iov - fast_iov;
                        rw->iter.iov += iov_off;
                }
                if (rw->fast_iov != fast_iov)
                        memcpy(rw->fast_iov + iov_off, fast_iov + iov_off,
                               sizeof(struct iovec) * iter->nr_segs);
        } else {
                req->flags |= REQ_F_NEED_CLEANUP;
        }
}

static inline int __io_alloc_async_data(struct io_kiocb *req)
{
        WARN_ON_ONCE(!io_op_defs[req->opcode].async_size);
        req->async_data = kmalloc(io_op_defs[req->opcode].async_size, GFP_KERNEL);
        return req->async_data == NULL;
}

static int io_alloc_async_data(struct io_kiocb *req)
{
        if (!io_op_defs[req->opcode].needs_async_data)
                return 0;

        return  __io_alloc_async_data(req);
}

static int io_setup_async_rw(struct io_kiocb *req, const struct iovec *iovec,
                             const struct iovec *fast_iov,
                             struct iov_iter *iter, bool force)
{
        if (!force && !io_op_defs[req->opcode].needs_async_data)
                return 0;
        if (!req->async_data) {
                if (__io_alloc_async_data(req))
                        return -ENOMEM;

                io_req_map_rw(req, iovec, fast_iov, iter);
        }
        return 0;
}

static inline int io_rw_prep_async(struct io_kiocb *req, int rw)
{
        struct io_async_rw *iorw = req->async_data;
        struct iovec *iov = iorw->fast_iov;
        ssize_t ret;

        ret = io_import_iovec(rw, req, &iov, &iorw->iter, false);
        if (unlikely(ret < 0))
                return ret;

        iorw->bytes_done = 0;
        iorw->free_iovec = iov;
        if (iov)
                req->flags |= REQ_F_NEED_CLEANUP;
        return 0;
}

static int io_read_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
{
        ssize_t ret;

        ret = io_prep_rw(req, sqe);
        if (ret)
                return ret;

        if (unlikely(!(req->file->f_mode & FMODE_READ)))
                return -EBADF;

        /* either don't need iovec imported or already have it */
        if (!req->async_data)
                return 0;
        return io_rw_prep_async(req, READ);
}

/*
 * This is our waitqueue callback handler, registered through lock_page_async()
 * when we initially tried to do the IO with the iocb armed our waitqueue.
 * This gets called when the page is unlocked, and we generally expect that to
 * happen when the page IO is completed and the page is now uptodate. This will
 * queue a task_work based retry of the operation, attempting to copy the data
 * again. If the latter fails because the page was NOT uptodate, then we will
 * do a thread based blocking retry of the operation. That's the unexpected
 * slow path.
 */
static int io_async_buf_func(struct wait_queue_entry *wait, unsigned mode,
                             int sync, void *arg)
{
        struct wait_page_queue *wpq;
        struct io_kiocb *req = wait->private;
        struct wait_page_key *key = arg;
        int ret;

        wpq = container_of(wait, struct wait_page_queue, wait);

        if (!wake_page_match(wpq, key))
                return 0;

        req->rw.kiocb.ki_flags &= ~IOCB_WAITQ;
        list_del_init(&wait->entry);

        init_task_work(&req->task_work, io_req_task_submit);
        percpu_ref_get(&req->ctx->refs);

        /* submit ref gets dropped, acquire a new one */
        refcount_inc(&req->refs);
        ret = io_req_task_work_add(req);
        if (unlikely(ret)) {
                struct task_struct *tsk;

                /* queue just for cancelation */
                init_task_work(&req->task_work, io_req_task_cancel);
                tsk = io_wq_get_task(req->ctx->io_wq);
                task_work_add(tsk, &req->task_work, TWA_NONE);
                wake_up_process(tsk);
        }
        return 1;
}

/*
 * This controls whether a given IO request should be armed for async page
 * based retry. If we return false here, the request is handed to the async
 * worker threads for retry. If we're doing buffered reads on a regular file,
 * we prepare a private wait_page_queue entry and retry the operation. This
 * will either succeed because the page is now uptodate and unlocked, or it
 * will register a callback when the page is unlocked at IO completion. Through
 * that callback, io_uring uses task_work to setup a retry of the operation.
 * That retry will attempt the buffered read again. The retry will generally
 * succeed, or in rare cases where it fails, we then fall back to using the
 * async worker threads for a blocking retry.
 */
static bool io_rw_should_retry(struct io_kiocb *req)
{
        struct io_async_rw *rw = req->async_data;
        struct wait_page_queue *wait = &rw->wpq;
        struct kiocb *kiocb = &req->rw.kiocb;

        /* never retry for NOWAIT, we just complete with -EAGAIN */
        if (req->flags & REQ_F_NOWAIT)
                return false;

        /* Only for buffered IO */
        if (kiocb->ki_flags & (IOCB_DIRECT | IOCB_HIPRI))
                return false;

        /*
         * just use poll if we can, and don't attempt if the fs doesn't
         * support callback based unlocks
         */
        if (file_can_poll(req->file) || !(req->file->f_mode & FMODE_BUF_RASYNC))
                return false;

        wait->wait.func = io_async_buf_func;
        wait->wait.private = req;
        wait->wait.flags = 0;
        INIT_LIST_HEAD(&wait->wait.entry);
        kiocb->ki_flags |= IOCB_WAITQ;
        kiocb->ki_flags &= ~IOCB_NOWAIT;
        kiocb->ki_waitq = wait;
        return true;
}

static int io_iter_do_read(struct io_kiocb *req, struct iov_iter *iter)
{
        if (req->file->f_op->read_iter)
                return call_read_iter(req->file, &req->rw.kiocb, iter);
        else if (req->file->f_op->read)
                return loop_rw_iter(READ, req, iter);
        else
                return -EINVAL;
}

static int io_read(struct io_kiocb *req, bool force_nonblock,
                   struct io_comp_state *cs)
{
        struct iovec inline_vecs[UIO_FASTIOV], *iovec = inline_vecs;
        struct kiocb *kiocb = &req->rw.kiocb;
        struct iov_iter __iter, *iter = &__iter;
        struct io_async_rw *rw = req->async_data;
        ssize_t io_size, ret, ret2;
        bool no_async;

        if (rw) {
                iter = &rw->iter;
                iovec = NULL;
        } else {
                ret = io_import_iovec(READ, req, &iovec, iter, !force_nonblock);
                if (ret < 0)
                        return ret;
        }
        io_size = iov_iter_count(iter);
        req->result = io_size;
        ret = 0;

        /* Ensure we clear previously set non-block flag */
        if (!force_nonblock)
                kiocb->ki_flags &= ~IOCB_NOWAIT;
        else
                kiocb->ki_flags |= IOCB_NOWAIT;


        /* If the file doesn't support async, just async punt */
        no_async = force_nonblock && !io_file_supports_async(req->file, READ);
        if (no_async)
                goto copy_iov;

        ret = rw_verify_area(READ, req->file, io_kiocb_ppos(kiocb), io_size);
        if (unlikely(ret))
                goto out_free;

        ret = io_iter_do_read(req, iter);

        if (!ret) {
                goto done;
        } else if (ret == -EIOCBQUEUED) {
                ret = 0;
                goto out_free;
        } else if (ret == -EAGAIN) {
                /* IOPOLL retry should happen for io-wq threads */
                if (!force_nonblock && !(req->ctx->flags & IORING_SETUP_IOPOLL))
                        goto done;
                /* no retry on NONBLOCK marked file */
                if (req->file->f_flags & O_NONBLOCK)
                        goto done;
                /* some cases will consume bytes even on error returns */
                iov_iter_revert(iter, io_size - iov_iter_count(iter));
                ret = 0;
                goto copy_iov;
        } else if (ret < 0) {
                /* make sure -ERESTARTSYS -> -EINTR is done */
                goto done;
        }

        /* read it all, or we did blocking attempt. no retry. */
        if (!iov_iter_count(iter) || !force_nonblock ||
            (req->file->f_flags & O_NONBLOCK))
                goto done;

        io_size -= ret;
copy_iov:
        ret2 = io_setup_async_rw(req, iovec, inline_vecs, iter, true);
        if (ret2) {
                ret = ret2;
                goto out_free;
        }
        if (no_async)
                return -EAGAIN;
        rw = req->async_data;
        /* it's copied and will be cleaned with ->io */
        iovec = NULL;
        /* now use our persistent iterator, if we aren't already */
        iter = &rw->iter;
retry:
        rw->bytes_done += ret;
        /* if we can retry, do so with the callbacks armed */
        if (!io_rw_should_retry(req)) {
                kiocb->ki_flags &= ~IOCB_WAITQ;
                return -EAGAIN;
        }

        /*
         * Now retry read with the IOCB_WAITQ parts set in the iocb. If we
         * get -EIOCBQUEUED, then we'll get a notification when the desired
         * page gets unlocked. We can also get a partial read here, and if we
         * do, then just retry at the new offset.
         */
        ret = io_iter_do_read(req, iter);
        if (ret == -EIOCBQUEUED) {
                ret = 0;
                goto out_free;
        } else if (ret > 0 && ret < io_size) {
                /* we got some bytes, but not all. retry. */
                goto retry;
        }
done:
        kiocb_done(kiocb, ret, cs);
        ret = 0;
out_free:
        /* it's reportedly faster than delegating the null check to kfree() */
        if (iovec)
                kfree(iovec);
        return ret;
}

static int io_write_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
{
        ssize_t ret;

        ret = io_prep_rw(req, sqe);
        if (ret)
                return ret;

        if (unlikely(!(req->file->f_mode & FMODE_WRITE)))
                return -EBADF;

        /* either don't need iovec imported or already have it */
        if (!req->async_data)
                return 0;
        return io_rw_prep_async(req, WRITE);
}

static int io_write(struct io_kiocb *req, bool force_nonblock,
                    struct io_comp_state *cs)
{
        struct iovec inline_vecs[UIO_FASTIOV], *iovec = inline_vecs;
        struct kiocb *kiocb = &req->rw.kiocb;
        struct iov_iter __iter, *iter = &__iter;
        struct io_async_rw *rw = req->async_data;
        ssize_t ret, ret2, io_size;

        if (rw) {
                iter = &rw->iter;
                iovec = NULL;
        } else {
                ret = io_import_iovec(WRITE, req, &iovec, iter, !force_nonblock);
                if (ret < 0)
                        return ret;
        }
        io_size = iov_iter_count(iter);
        req->result = io_size;

        /* Ensure we clear previously set non-block flag */
        if (!force_nonblock)
                kiocb->ki_flags &= ~IOCB_NOWAIT;
        else
                kiocb->ki_flags |= IOCB_NOWAIT;

        /* If the file doesn't support async, just async punt */
        if (force_nonblock && !io_file_supports_async(req->file, WRITE))
                goto copy_iov;

        /* file path doesn't support NOWAIT for non-direct_IO */
        if (force_nonblock && !(kiocb->ki_flags & IOCB_DIRECT) &&
            (req->flags & REQ_F_ISREG))
                goto copy_iov;

        ret = rw_verify_area(WRITE, req->file, io_kiocb_ppos(kiocb), io_size);
        if (unlikely(ret))
                goto out_free;

        /*
         * Open-code file_start_write here to grab freeze protection,
         * which will be released by another thread in
         * io_complete_rw().  Fool lockdep by telling it the lock got
         * released so that it doesn't complain about the held lock when
         * we return to userspace.
         */
        if (req->flags & REQ_F_ISREG) {
                sb_start_write(file_inode(req->file)->i_sb);
                __sb_writers_release(file_inode(req->file)->i_sb,
                                        SB_FREEZE_WRITE);
        }
        kiocb->ki_flags |= IOCB_WRITE;

        if (req->file->f_op->write_iter)
                ret2 = call_write_iter(req->file, kiocb, iter);
        else if (req->file->f_op->write)
                ret2 = loop_rw_iter(WRITE, req, iter);
        else
                ret2 = -EINVAL;

        /*
         * Raw bdev writes will return -EOPNOTSUPP for IOCB_NOWAIT. Just
         * retry them without IOCB_NOWAIT.
         */
        if (ret2 == -EOPNOTSUPP && (kiocb->ki_flags & IOCB_NOWAIT))
                ret2 = -EAGAIN;
        /* no retry on NONBLOCK marked file */
        if (ret2 == -EAGAIN && (req->file->f_flags & O_NONBLOCK))
                goto done;
        if (!force_nonblock || ret2 != -EAGAIN) {
                /* IOPOLL retry should happen for io-wq threads */
                if ((req->ctx->flags & IORING_SETUP_IOPOLL) && ret2 == -EAGAIN)
                        goto copy_iov;
done:
                kiocb_done(kiocb, ret2, cs);
        } else {
copy_iov:
                /* some cases will consume bytes even on error returns */
                iov_iter_revert(iter, io_size - iov_iter_count(iter));
                ret = io_setup_async_rw(req, iovec, inline_vecs, iter, false);
                if (!ret)
                        return -EAGAIN;
        }
out_free:
        /* it's reportedly faster than delegating the null check to kfree() */
        if (iovec)
                kfree(iovec);
        return ret;
}

static int io_renameat_prep(struct io_kiocb *req,
                            const struct io_uring_sqe *sqe)
{
        struct io_rename *ren = &req->rename;
        const char __user *oldf, *newf;

        if (unlikely(req->flags & REQ_F_FIXED_FILE))
                return -EBADF;

        ren->old_dfd = READ_ONCE(sqe->fd);
        oldf = u64_to_user_ptr(READ_ONCE(sqe->addr));
        newf = u64_to_user_ptr(READ_ONCE(sqe->addr2));
        ren->new_dfd = READ_ONCE(sqe->len);
        ren->flags = READ_ONCE(sqe->rename_flags);

        ren->oldpath = getname(oldf);
        if (IS_ERR(ren->oldpath))
                return PTR_ERR(ren->oldpath);

        ren->newpath = getname(newf);
        if (IS_ERR(ren->newpath)) {
                putname(ren->oldpath);
                return PTR_ERR(ren->newpath);
        }

        req->flags |= REQ_F_NEED_CLEANUP;
        return 0;
}

static int io_renameat(struct io_kiocb *req, bool force_nonblock)
{
        struct io_rename *ren = &req->rename;
        int ret;

        if (force_nonblock)
                return -EAGAIN;

        ret = do_renameat2(ren->old_dfd, ren->oldpath, ren->new_dfd,
                                ren->newpath, ren->flags);

        req->flags &= ~REQ_F_NEED_CLEANUP;
        if (ret < 0)
                req_set_fail_links(req);
        io_req_complete(req, ret);
        return 0;
}

static int io_unlinkat_prep(struct io_kiocb *req,
                            const struct io_uring_sqe *sqe)
{
        struct io_unlink *un = &req->unlink;
        const char __user *fname;

        if (unlikely(req->flags & REQ_F_FIXED_FILE))
                return -EBADF;

        un->dfd = READ_ONCE(sqe->fd);

        un->flags = READ_ONCE(sqe->unlink_flags);
        if (un->flags & ~AT_REMOVEDIR)
                return -EINVAL;

        fname = u64_to_user_ptr(READ_ONCE(sqe->addr));
        un->filename = getname(fname);
        if (IS_ERR(un->filename))
                return PTR_ERR(un->filename);

        req->flags |= REQ_F_NEED_CLEANUP;
        return 0;
}

static int io_unlinkat(struct io_kiocb *req, bool force_nonblock)
{
        struct io_unlink *un = &req->unlink;
        int ret;

        if (force_nonblock)
                return -EAGAIN;

        if (un->flags & AT_REMOVEDIR)
                ret = do_rmdir(un->dfd, un->filename);
        else
                ret = do_unlinkat(un->dfd, un->filename);

        req->flags &= ~REQ_F_NEED_CLEANUP;
        if (ret < 0)
                req_set_fail_links(req);
        io_req_complete(req, ret);
        return 0;
}

static int io_shutdown_prep(struct io_kiocb *req,
                            const struct io_uring_sqe *sqe)
{
#if defined(CONFIG_NET)
        if (unlikely(req->ctx->flags & IORING_SETUP_IOPOLL))
                return -EINVAL;
        if (sqe->ioprio || sqe->off || sqe->addr || sqe->rw_flags ||
            sqe->buf_index)
                return -EINVAL;

        req->shutdown.how = READ_ONCE(sqe->len);
        return 0;
#else
        return -EOPNOTSUPP;
#endif
}

static int io_shutdown(struct io_kiocb *req, bool force_nonblock)
{
#if defined(CONFIG_NET)
        struct socket *sock;
        int ret;

        if (force_nonblock)
                return -EAGAIN;

        sock = sock_from_file(req->file);
        if (unlikely(!sock))
                return -ENOTSOCK;

        ret = __sys_shutdown_sock(sock, req->shutdown.how);
        if (ret < 0)
                req_set_fail_links(req);
        io_req_complete(req, ret);
        return 0;
#else
        return -EOPNOTSUPP;
#endif
}

static int __io_splice_prep(struct io_kiocb *req,
                            const struct io_uring_sqe *sqe)
{
        struct io_splice* sp = &req->splice;
        unsigned int valid_flags = SPLICE_F_FD_IN_FIXED | SPLICE_F_ALL;

        if (unlikely(req->ctx->flags & IORING_SETUP_IOPOLL))
                return -EINVAL;

        sp->file_in = NULL;
        sp->len = READ_ONCE(sqe->len);
        sp->flags = READ_ONCE(sqe->splice_flags);

        if (unlikely(sp->flags & ~valid_flags))
                return -EINVAL;

        sp->file_in = io_file_get(NULL, req, READ_ONCE(sqe->splice_fd_in),
                                  (sp->flags & SPLICE_F_FD_IN_FIXED));
        if (!sp->file_in)
                return -EBADF;
        req->flags |= REQ_F_NEED_CLEANUP;

        if (!S_ISREG(file_inode(sp->file_in)->i_mode)) {
                /*
                 * Splice operation will be punted aync, and here need to
                 * modify io_wq_work.flags, so initialize io_wq_work firstly.
                 */
                io_req_init_async(req);
                req->work.flags |= IO_WQ_WORK_UNBOUND;
        }

        return 0;
}

static int io_tee_prep(struct io_kiocb *req,
                       const struct io_uring_sqe *sqe)
{
        if (READ_ONCE(sqe->splice_off_in) || READ_ONCE(sqe->off))
                return -EINVAL;
        return __io_splice_prep(req, sqe);
}

static int io_tee(struct io_kiocb *req, bool force_nonblock)
{
        struct io_splice *sp = &req->splice;
        struct file *in = sp->file_in;
        struct file *out = sp->file_out;
        unsigned int flags = sp->flags & ~SPLICE_F_FD_IN_FIXED;
        long ret = 0;

        if (force_nonblock)
                return -EAGAIN;
        if (sp->len)
                ret = do_tee(in, out, sp->len, flags);

        io_put_file(req, in, (sp->flags & SPLICE_F_FD_IN_FIXED));
        req->flags &= ~REQ_F_NEED_CLEANUP;

        if (ret != sp->len)
                req_set_fail_links(req);
        io_req_complete(req, ret);
        return 0;
}

static int io_splice_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
{
        struct io_splice* sp = &req->splice;

        sp->off_in = READ_ONCE(sqe->splice_off_in);
        sp->off_out = READ_ONCE(sqe->off);
        return __io_splice_prep(req, sqe);
}

static int io_splice(struct io_kiocb *req, bool force_nonblock)
{
        struct io_splice *sp = &req->splice;
        struct file *in = sp->file_in;
        struct file *out = sp->file_out;
        unsigned int flags = sp->flags & ~SPLICE_F_FD_IN_FIXED;
        loff_t *poff_in, *poff_out;
        long ret = 0;

        if (force_nonblock)
                return -EAGAIN;

        poff_in = (sp->off_in == -1) ? NULL : &sp->off_in;
        poff_out = (sp->off_out == -1) ? NULL : &sp->off_out;

        if (sp->len)
                ret = do_splice(in, poff_in, out, poff_out, sp->len, flags);

        io_put_file(req, in, (sp->flags & SPLICE_F_FD_IN_FIXED));
        req->flags &= ~REQ_F_NEED_CLEANUP;

        if (ret != sp->len)
                req_set_fail_links(req);
        io_req_complete(req, ret);
        return 0;
}

/*
 * IORING_OP_NOP just posts a completion event, nothing else.
 */
static int io_nop(struct io_kiocb *req, struct io_comp_state *cs)
{
        struct io_ring_ctx *ctx = req->ctx;

        if (unlikely(ctx->flags & IORING_SETUP_IOPOLL))
                return -EINVAL;

        __io_req_complete(req, 0, 0, cs);
        return 0;
}

static int io_prep_fsync(struct io_kiocb *req, const struct io_uring_sqe *sqe)
{
        struct io_ring_ctx *ctx = req->ctx;

        if (!req->file)
                return -EBADF;

        if (unlikely(ctx->flags & IORING_SETUP_IOPOLL))
                return -EINVAL;
        if (unlikely(sqe->addr || sqe->ioprio || sqe->buf_index))
                return -EINVAL;

        req->sync.flags = READ_ONCE(sqe->fsync_flags);
        if (unlikely(req->sync.flags & ~IORING_FSYNC_DATASYNC))
                return -EINVAL;

        req->sync.off = READ_ONCE(sqe->off);
        req->sync.len = READ_ONCE(sqe->len);
        return 0;
}

static int io_fsync(struct io_kiocb *req, bool force_nonblock)
{
        loff_t end = req->sync.off + req->sync.len;
        int ret;

        /* fsync always requires a blocking context */
        if (force_nonblock)
                return -EAGAIN;

        ret = vfs_fsync_range(req->file, req->sync.off,
                                end > 0 ? end : LLONG_MAX,
                                req->sync.flags & IORING_FSYNC_DATASYNC);
        if (ret < 0)
                req_set_fail_links(req);
        io_req_complete(req, ret);
        return 0;
}

static int io_fallocate_prep(struct io_kiocb *req,
                             const struct io_uring_sqe *sqe)
{
        if (sqe->ioprio || sqe->buf_index || sqe->rw_flags)
                return -EINVAL;
        if (unlikely(req->ctx->flags & IORING_SETUP_IOPOLL))
                return -EINVAL;

        req->sync.off = READ_ONCE(sqe->off);
        req->sync.len = READ_ONCE(sqe->addr);
        req->sync.mode = READ_ONCE(sqe->len);
        return 0;
}

static int io_fallocate(struct io_kiocb *req, bool force_nonblock)
{
        int ret;

        /* fallocate always requiring blocking context */
        if (force_nonblock)
                return -EAGAIN;
        ret = vfs_fallocate(req->file, req->sync.mode, req->sync.off,
                                req->sync.len);
        if (ret < 0)
                req_set_fail_links(req);
        io_req_complete(req, ret);
        return 0;
}

static int __io_openat_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
{
        const char __user *fname;
        int ret;

        if (unlikely(sqe->ioprio || sqe->buf_index))
                return -EINVAL;
        if (unlikely(req->flags & REQ_F_FIXED_FILE))
                return -EBADF;

        /* open.how should be already initialised */
        if (!(req->open.how.flags & O_PATH) && force_o_largefile())
                req->open.how.flags |= O_LARGEFILE;

        req->open.dfd = READ_ONCE(sqe->fd);
        fname = u64_to_user_ptr(READ_ONCE(sqe->addr));
        req->open.filename = getname(fname);
        if (IS_ERR(req->open.filename)) {
                ret = PTR_ERR(req->open.filename);
                req->open.filename = NULL;
                return ret;
        }
        req->open.nofile = rlimit(RLIMIT_NOFILE);
        req->open.ignore_nonblock = false;
        req->flags |= REQ_F_NEED_CLEANUP;
        return 0;
}

static int io_openat_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
{
        u64 flags, mode;

        if (unlikely(req->ctx->flags & IORING_SETUP_IOPOLL))
                return -EINVAL;
        mode = READ_ONCE(sqe->len);
        flags = READ_ONCE(sqe->open_flags);
        req->open.how = build_open_how(flags, mode);
        return __io_openat_prep(req, sqe);
}

static int io_openat2_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
{
        struct open_how __user *how;
        size_t len;
        int ret;

        if (unlikely(req->ctx->flags & IORING_SETUP_IOPOLL))
                return -EINVAL;
        how = u64_to_user_ptr(READ_ONCE(sqe->addr2));
        len = READ_ONCE(sqe->len);
        if (len < OPEN_HOW_SIZE_VER0)
                return -EINVAL;

        ret = copy_struct_from_user(&req->open.how, sizeof(req->open.how), how,
                                        len);
        if (ret)
                return ret;

        return __io_openat_prep(req, sqe);
}

static int io_openat2(struct io_kiocb *req, bool force_nonblock)
{
        struct open_flags op;
        struct file *file;
        int ret;

        if (force_nonblock && !req->open.ignore_nonblock)
                return -EAGAIN;

        ret = build_open_flags(&req->open.how, &op);
        if (ret)
                goto err;

        ret = __get_unused_fd_flags(req->open.how.flags, req->open.nofile);
        if (ret < 0)
                goto err;

        file = do_filp_open(req->open.dfd, req->open.filename, &op);
        if (IS_ERR(file)) {
                put_unused_fd(ret);
                ret = PTR_ERR(file);
                /*
                 * A work-around to ensure that /proc/self works that way
                 * that it should - if we get -EOPNOTSUPP back, then assume
                 * that proc_self_get_link() failed us because we're in async
                 * context. We should be safe to retry this from the task
                 * itself with force_nonblock == false set, as it should not
                 * block on lookup. Would be nice to know this upfront and
                 * avoid the async dance, but doesn't seem feasible.
                 */
                if (ret == -EOPNOTSUPP && io_wq_current_is_worker()) {
                        req->open.ignore_nonblock = true;
                        refcount_inc(&req->refs);
                        io_req_task_queue(req);
                        return 0;
                }
        } else {
                fsnotify_open(file);
                fd_install(ret, file);
        }
err:
        putname(req->open.filename);
        req->flags &= ~REQ_F_NEED_CLEANUP;
        if (ret < 0)
                req_set_fail_links(req);
        io_req_complete(req, ret);
        return 0;
}

static int io_openat(struct io_kiocb *req, bool force_nonblock)
{
        return io_openat2(req, force_nonblock);
}

static int io_remove_buffers_prep(struct io_kiocb *req,
                                  const struct io_uring_sqe *sqe)
{
        struct io_provide_buf *p = &req->pbuf;
        u64 tmp;

        if (sqe->ioprio || sqe->rw_flags || sqe->addr || sqe->len || sqe->off)
                return -EINVAL;

        tmp = READ_ONCE(sqe->fd);
        if (!tmp || tmp > USHRT_MAX)
                return -EINVAL;

        memset(p, 0, sizeof(*p));
        p->nbufs = tmp;
        p->bgid = READ_ONCE(sqe->buf_group);
        return 0;
}

static int __io_remove_buffers(struct io_ring_ctx *ctx, struct io_buffer *buf,
                               int bgid, unsigned nbufs)
{
        unsigned i = 0;

        /* shouldn't happen */
        if (!nbufs)
                return 0;

        /* the head kbuf is the list itself */
        while (!list_empty(&buf->list)) {
                struct io_buffer *nxt;

                nxt = list_first_entry(&buf->list, struct io_buffer, list);
                list_del(&nxt->list);
                kfree(nxt);
                if (++i == nbufs)
                        return i;
        }
        i++;
        kfree(buf);
        idr_remove(&ctx->io_buffer_idr, bgid);

        return i;
}

static int io_remove_buffers(struct io_kiocb *req, bool force_nonblock,
                             struct io_comp_state *cs)
{
        struct io_provide_buf *p = &req->pbuf;
        struct io_ring_ctx *ctx = req->ctx;
        struct io_buffer *head;
        int ret = 0;

        io_ring_submit_lock(ctx, !force_nonblock);

        lockdep_assert_held(&ctx->uring_lock);

        ret = -ENOENT;
        head = idr_find(&ctx->io_buffer_idr, p->bgid);
        if (head)
                ret = __io_remove_buffers(ctx, head, p->bgid, p->nbufs);
        if (ret < 0)
                req_set_fail_links(req);

        /* need to hold the lock to complete IOPOLL requests */
        if (ctx->flags & IORING_SETUP_IOPOLL) {
                __io_req_complete(req, ret, 0, cs);
                io_ring_submit_unlock(ctx, !force_nonblock);
        } else {
                io_ring_submit_unlock(ctx, !force_nonblock);
                __io_req_complete(req, ret, 0, cs);
        }
        return 0;
}

static int io_provide_buffers_prep(struct io_kiocb *req,
                                   const struct io_uring_sqe *sqe)
{
        struct io_provide_buf *p = &req->pbuf;
        u64 tmp;

        if (sqe->ioprio || sqe->rw_flags)
                return -EINVAL;

        tmp = READ_ONCE(sqe->fd);
        if (!tmp || tmp > USHRT_MAX)
                return -E2BIG;
        p->nbufs = tmp;
        p->addr = READ_ONCE(sqe->addr);
        p->len = READ_ONCE(sqe->len);

        if (!access_ok(u64_to_user_ptr(p->addr), (p->len * p->nbufs)))
                return -EFAULT;

        p->bgid = READ_ONCE(sqe->buf_group);
        tmp = READ_ONCE(sqe->off);
        if (tmp > USHRT_MAX)
                return -E2BIG;
        p->bid = tmp;
        return 0;
}

static int io_add_buffers(struct io_provide_buf *pbuf, struct io_buffer **head)
{
        struct io_buffer *buf;
        u64 addr = pbuf->addr;
        int i, bid = pbuf->bid;

        for (i = 0; i < pbuf->nbufs; i++) {
                buf = kmalloc(sizeof(*buf), GFP_KERNEL);
                if (!buf)
                        break;

                buf->addr = addr;
                buf->len = pbuf->len;
                buf->bid = bid;
                addr += pbuf->len;
                bid++;
                if (!*head) {
                        INIT_LIST_HEAD(&buf->list);
                        *head = buf;
                } else {
                        list_add_tail(&buf->list, &(*head)->list);
                }
        }

        return i ? i : -ENOMEM;
}

static int io_provide_buffers(struct io_kiocb *req, bool force_nonblock,
                              struct io_comp_state *cs)
{
        struct io_provide_buf *p = &req->pbuf;
        struct io_ring_ctx *ctx = req->ctx;
        struct io_buffer *head, *list;
        int ret = 0;

        io_ring_submit_lock(ctx, !force_nonblock);

        lockdep_assert_held(&ctx->uring_lock);

        list = head = idr_find(&ctx->io_buffer_idr, p->bgid);

        ret = io_add_buffers(p, &head);
        if (ret < 0)
                goto out;

        if (!list) {
                ret = idr_alloc(&ctx->io_buffer_idr, head, p->bgid, p->bgid + 1,
                                        GFP_KERNEL);
                if (ret < 0) {
                        __io_remove_buffers(ctx, head, p->bgid, -1U);
                        goto out;
                }
        }
out:
        if (ret < 0)
                req_set_fail_links(req);

        /* need to hold the lock to complete IOPOLL requests */
        if (ctx->flags & IORING_SETUP_IOPOLL) {
                __io_req_complete(req, ret, 0, cs);
                io_ring_submit_unlock(ctx, !force_nonblock);
        } else {
                io_ring_submit_unlock(ctx, !force_nonblock);
                __io_req_complete(req, ret, 0, cs);
        }
        return 0;
}

static int io_epoll_ctl_prep(struct io_kiocb *req,
                             const struct io_uring_sqe *sqe)
{
#if defined(CONFIG_EPOLL)
        if (sqe->ioprio || sqe->buf_index)
                return -EINVAL;
        if (unlikely(req->ctx->flags & (IORING_SETUP_IOPOLL | IORING_SETUP_SQPOLL)))
                return -EINVAL;

        req->epoll.epfd = READ_ONCE(sqe->fd);
        req->epoll.op = READ_ONCE(sqe->len);
        req->epoll.fd = READ_ONCE(sqe->off);

        if (ep_op_has_event(req->epoll.op)) {
                struct epoll_event __user *ev;

                ev = u64_to_user_ptr(READ_ONCE(sqe->addr));
                if (copy_from_user(&req->epoll.event, ev, sizeof(*ev)))
                        return -EFAULT;
        }

        return 0;
#else
        return -EOPNOTSUPP;
#endif
}

static int io_epoll_ctl(struct io_kiocb *req, bool force_nonblock,
                        struct io_comp_state *cs)
{
#if defined(CONFIG_EPOLL)
        struct io_epoll *ie = &req->epoll;
        int ret;

        ret = do_epoll_ctl(ie->epfd, ie->op, ie->fd, &ie->event, force_nonblock);
        if (force_nonblock && ret == -EAGAIN)
                return -EAGAIN;

        if (ret < 0)
                req_set_fail_links(req);
        __io_req_complete(req, ret, 0, cs);
        return 0;
#else
        return -EOPNOTSUPP;
#endif
}

static int io_madvise_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
{
#if defined(CONFIG_ADVISE_SYSCALLS) && defined(CONFIG_MMU)
        if (sqe->ioprio || sqe->buf_index || sqe->off)
                return -EINVAL;
        if (unlikely(req->ctx->flags & IORING_SETUP_IOPOLL))
                return -EINVAL;

        req->madvise.addr = READ_ONCE(sqe->addr);
        req->madvise.len = READ_ONCE(sqe->len);
        req->madvise.advice = READ_ONCE(sqe->fadvise_advice);
        return 0;
#else
        return -EOPNOTSUPP;
#endif
}

static int io_madvise(struct io_kiocb *req, bool force_nonblock)
{
#if defined(CONFIG_ADVISE_SYSCALLS) && defined(CONFIG_MMU)
        struct io_madvise *ma = &req->madvise;
        int ret;

        if (force_nonblock)
                return -EAGAIN;

        ret = do_madvise(current->mm, ma->addr, ma->len, ma->advice);
        if (ret < 0)
                req_set_fail_links(req);
        io_req_complete(req, ret);
        return 0;
#else
        return -EOPNOTSUPP;
#endif
}

static int io_fadvise_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
{
        if (sqe->ioprio || sqe->buf_index || sqe->addr)
                return -EINVAL;
        if (unlikely(req->ctx->flags & IORING_SETUP_IOPOLL))
                return -EINVAL;

        req->fadvise.offset = READ_ONCE(sqe->off);
        req->fadvise.len = READ_ONCE(sqe->len);
        req->fadvise.advice = READ_ONCE(sqe->fadvise_advice);
        return 0;
}

static int io_fadvise(struct io_kiocb *req, bool force_nonblock)
{
        struct io_fadvise *fa = &req->fadvise;
        int ret;

        if (force_nonblock) {
                switch (fa->advice) {
                case POSIX_FADV_NORMAL:
                case POSIX_FADV_RANDOM:
                case POSIX_FADV_SEQUENTIAL:
                        break;
                default:
                        return -EAGAIN;
                }
        }

        ret = vfs_fadvise(req->file, fa->offset, fa->len, fa->advice);
        if (ret < 0)
                req_set_fail_links(req);
        io_req_complete(req, ret);
        return 0;
}

static int io_statx_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
{
        if (unlikely(req->ctx->flags & (IORING_SETUP_IOPOLL | IORING_SETUP_SQPOLL)))
                return -EINVAL;
        if (sqe->ioprio || sqe->buf_index)
                return -EINVAL;
        if (req->flags & REQ_F_FIXED_FILE)
                return -EBADF;

        req->statx.dfd = READ_ONCE(sqe->fd);
        req->statx.mask = READ_ONCE(sqe->len);
        req->statx.filename = u64_to_user_ptr(READ_ONCE(sqe->addr));
        req->statx.buffer = u64_to_user_ptr(READ_ONCE(sqe->addr2));
        req->statx.flags = READ_ONCE(sqe->statx_flags);

        return 0;
}

static int io_statx(struct io_kiocb *req, bool force_nonblock)
{
        struct io_statx *ctx = &req->statx;
        int ret;

        if (force_nonblock) {
                /* only need file table for an actual valid fd */
                if (ctx->dfd == -1 || ctx->dfd == AT_FDCWD)
                        req->flags |= REQ_F_NO_FILE_TABLE;
                return -EAGAIN;
        }

        ret = do_statx(ctx->dfd, ctx->filename, ctx->flags, ctx->mask,
                       ctx->buffer);

        if (ret < 0)
                req_set_fail_links(req);
        io_req_complete(req, ret);
        return 0;
}

static int io_close_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
{
        /*
         * If we queue this for async, it must not be cancellable. That would
         * leave the 'file' in an undeterminate state, and here need to modify
         * io_wq_work.flags, so initialize io_wq_work firstly.
         */
        io_req_init_async(req);
        req->work.flags |= IO_WQ_WORK_NO_CANCEL;

        if (unlikely(req->ctx->flags & IORING_SETUP_IOPOLL))
                return -EINVAL;
        if (sqe->ioprio || sqe->off || sqe->addr || sqe->len ||
            sqe->rw_flags || sqe->buf_index)
                return -EINVAL;
        if (req->flags & REQ_F_FIXED_FILE)
                return -EBADF;

        req->close.fd = READ_ONCE(sqe->fd);
        if ((req->file && req->file->f_op == &io_uring_fops))
                return -EBADF;

        req->close.put_file = NULL;
        return 0;
}

static int io_close(struct io_kiocb *req, bool force_nonblock,
                    struct io_comp_state *cs)
{
        struct io_close *close = &req->close;
        int ret;

        /* might be already done during nonblock submission */
        if (!close->put_file) {
                ret = close_fd_get_file(close->fd, &close->put_file);
                if (ret < 0)
                        return (ret == -ENOENT) ? -EBADF : ret;
        }

        /* if the file has a flush method, be safe and punt to async */
        if (close->put_file->f_op->flush && force_nonblock) {
                /* was never set, but play safe */
                req->flags &= ~REQ_F_NOWAIT;
                /* avoid grabbing files - we don't need the files */
                req->flags |= REQ_F_NO_FILE_TABLE;
                return -EAGAIN;
        }

        /* No ->flush() or already async, safely close from here */
        ret = filp_close(close->put_file, req->work.identity->files);
        if (ret < 0)
                req_set_fail_links(req);
        fput(close->put_file);
        close->put_file = NULL;
        __io_req_complete(req, ret, 0, cs);
        return 0;
}

static int io_prep_sfr(struct io_kiocb *req, const struct io_uring_sqe *sqe)
{
        struct io_ring_ctx *ctx = req->ctx;

        if (!req->file)
                return -EBADF;

        if (unlikely(ctx->flags & IORING_SETUP_IOPOLL))
                return -EINVAL;
        if (unlikely(sqe->addr || sqe->ioprio || sqe->buf_index))
                return -EINVAL;

        req->sync.off = READ_ONCE(sqe->off);
        req->sync.len = READ_ONCE(sqe->len);
        req->sync.flags = READ_ONCE(sqe->sync_range_flags);
        return 0;
}

static int io_sync_file_range(struct io_kiocb *req, bool force_nonblock)
{
        int ret;

        /* sync_file_range always requires a blocking context */
        if (force_nonblock)
                return -EAGAIN;

        ret = sync_file_range(req->file, req->sync.off, req->sync.len,
                                req->sync.flags);
        if (ret < 0)
                req_set_fail_links(req);
        io_req_complete(req, ret);
        return 0;
}

#if defined(CONFIG_NET)
static int io_setup_async_msg(struct io_kiocb *req,
                              struct io_async_msghdr *kmsg)
{
        struct io_async_msghdr *async_msg = req->async_data;

        if (async_msg)
                return -EAGAIN;
        if (io_alloc_async_data(req)) {
                if (kmsg->iov != kmsg->fast_iov)
                        kfree(kmsg->iov);
                return -ENOMEM;
        }
        async_msg = req->async_data;
        req->flags |= REQ_F_NEED_CLEANUP;
        memcpy(async_msg, kmsg, sizeof(*kmsg));
        return -EAGAIN;
}

static int io_sendmsg_copy_hdr(struct io_kiocb *req,
                               struct io_async_msghdr *iomsg)
{
        iomsg->iov = iomsg->fast_iov;
        iomsg->msg.msg_name = &iomsg->addr;
        return sendmsg_copy_msghdr(&iomsg->msg, req->sr_msg.umsg,
                                   req->sr_msg.msg_flags, &iomsg->iov);
}

static int io_sendmsg_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
{
        struct io_async_msghdr *async_msg = req->async_data;
        struct io_sr_msg *sr = &req->sr_msg;
        int ret;

        if (unlikely(req->ctx->flags & IORING_SETUP_IOPOLL))
                return -EINVAL;

        sr->msg_flags = READ_ONCE(sqe->msg_flags);
        sr->umsg = u64_to_user_ptr(READ_ONCE(sqe->addr));
        sr->len = READ_ONCE(sqe->len);

#ifdef CONFIG_COMPAT
        if (req->ctx->compat)
                sr->msg_flags |= MSG_CMSG_COMPAT;
#endif

        if (!async_msg || !io_op_defs[req->opcode].needs_async_data)
                return 0;
        ret = io_sendmsg_copy_hdr(req, async_msg);
        if (!ret)
                req->flags |= REQ_F_NEED_CLEANUP;
        return ret;
}

static int io_sendmsg(struct io_kiocb *req, bool force_nonblock,
                      struct io_comp_state *cs)
{
        struct io_async_msghdr iomsg, *kmsg;
        struct socket *sock;
        unsigned flags;
        int ret;

        sock = sock_from_file(req->file);
        if (unlikely(!sock))
                return -ENOTSOCK;

        if (req->async_data) {
                kmsg = req->async_data;
                kmsg->msg.msg_name = &kmsg->addr;
                /* if iov is set, it's allocated already */
                if (!kmsg->iov)
                        kmsg->iov = kmsg->fast_iov;
                kmsg->msg.msg_iter.iov = kmsg->iov;
        } else {
                ret = io_sendmsg_copy_hdr(req, &iomsg);
                if (ret)
                        return ret;
                kmsg = &iomsg;
        }

        flags = req->sr_msg.msg_flags;
        if (flags & MSG_DONTWAIT)
                req->flags |= REQ_F_NOWAIT;
        else if (force_nonblock)
                flags |= MSG_DONTWAIT;

        ret = __sys_sendmsg_sock(sock, &kmsg->msg, flags);
        if (force_nonblock && ret == -EAGAIN)
                return io_setup_async_msg(req, kmsg);
        if (ret == -ERESTARTSYS)
                ret = -EINTR;

        if (kmsg->iov != kmsg->fast_iov)
                kfree(kmsg->iov);
        req->flags &= ~REQ_F_NEED_CLEANUP;
        if (ret < 0)
                req_set_fail_links(req);
        __io_req_complete(req, ret, 0, cs);
        return 0;
}

static int io_send(struct io_kiocb *req, bool force_nonblock,
                   struct io_comp_state *cs)
{
        struct io_sr_msg *sr = &req->sr_msg;
        struct msghdr msg;
        struct iovec iov;
        struct socket *sock;
        unsigned flags;
        int ret;

        sock = sock_from_file(req->file);
        if (unlikely(!sock))
                return -ENOTSOCK;

        ret = import_single_range(WRITE, sr->buf, sr->len, &iov, &msg.msg_iter);
        if (unlikely(ret))
                return ret;

        msg.msg_name = NULL;
        msg.msg_control = NULL;
        msg.msg_controllen = 0;
        msg.msg_namelen = 0;

        flags = req->sr_msg.msg_flags;
        if (flags & MSG_DONTWAIT)
                req->flags |= REQ_F_NOWAIT;
        else if (force_nonblock)
                flags |= MSG_DONTWAIT;

        msg.msg_flags = flags;
        ret = sock_sendmsg(sock, &msg);
        if (force_nonblock && ret == -EAGAIN)
                return -EAGAIN;
        if (ret == -ERESTARTSYS)
                ret = -EINTR;

        if (ret < 0)
                req_set_fail_links(req);
        __io_req_complete(req, ret, 0, cs);
        return 0;
}

static int __io_recvmsg_copy_hdr(struct io_kiocb *req,
                                 struct io_async_msghdr *iomsg)
{
        struct io_sr_msg *sr = &req->sr_msg;
        struct iovec __user *uiov;
        size_t iov_len;
        int ret;

        ret = __copy_msghdr_from_user(&iomsg->msg, sr->umsg,
                                        &iomsg->uaddr, &uiov, &iov_len);
        if (ret)
                return ret;

        if (req->flags & REQ_F_BUFFER_SELECT) {
                if (iov_len > 1)
                        return -EINVAL;
                if (copy_from_user(iomsg->iov, uiov, sizeof(*uiov)))
                        return -EFAULT;
                sr->len = iomsg->iov[0].iov_len;
                iov_iter_init(&iomsg->msg.msg_iter, READ, iomsg->iov, 1,
                                sr->len);
                iomsg->iov = NULL;
        } else {
                ret = __import_iovec(READ, uiov, iov_len, UIO_FASTIOV,
                                     &iomsg->iov, &iomsg->msg.msg_iter,
                                     false);
                if (ret > 0)
                        ret = 0;
        }

        return ret;
}

#ifdef CONFIG_COMPAT
static int __io_compat_recvmsg_copy_hdr(struct io_kiocb *req,
                                        struct io_async_msghdr *iomsg)
{
        struct compat_msghdr __user *msg_compat;
        struct io_sr_msg *sr = &req->sr_msg;
        struct compat_iovec __user *uiov;
        compat_uptr_t ptr;
        compat_size_t len;
        int ret;

        msg_compat = (struct compat_msghdr __user *) sr->umsg;
        ret = __get_compat_msghdr(&iomsg->msg, msg_compat, &iomsg->uaddr,
                                        &ptr, &len);
        if (ret)
                return ret;

        uiov = compat_ptr(ptr);
        if (req->flags & REQ_F_BUFFER_SELECT) {
                compat_ssize_t clen;

                if (len > 1)
                        return -EINVAL;
                if (!access_ok(uiov, sizeof(*uiov)))
                        return -EFAULT;
                if (__get_user(clen, &uiov->iov_len))
                        return -EFAULT;
                if (clen < 0)
                        return -EINVAL;
                sr->len = clen;
                iomsg->iov[0].iov_len = clen;
                iomsg->iov = NULL;
        } else {
                ret = __import_iovec(READ, (struct iovec __user *)uiov, len,
                                   UIO_FASTIOV, &iomsg->iov,
                                   &iomsg->msg.msg_iter, true);
                if (ret < 0)
                        return ret;
        }

        return 0;
}
#endif

static int io_recvmsg_copy_hdr(struct io_kiocb *req,
                               struct io_async_msghdr *iomsg)
{
        iomsg->msg.msg_name = &iomsg->addr;
        iomsg->iov = iomsg->fast_iov;

#ifdef CONFIG_COMPAT
        if (req->ctx->compat)
                return __io_compat_recvmsg_copy_hdr(req, iomsg);
#endif

        return __io_recvmsg_copy_hdr(req, iomsg);
}

static struct io_buffer *io_recv_buffer_select(struct io_kiocb *req,
                                               bool needs_lock)
{
        struct io_sr_msg *sr = &req->sr_msg;
        struct io_buffer *kbuf;

        kbuf = io_buffer_select(req, &sr->len, sr->bgid, sr->kbuf, needs_lock);
        if (IS_ERR(kbuf))
                return kbuf;

        sr->kbuf = kbuf;
        req->flags |= REQ_F_BUFFER_SELECTED;
        return kbuf;
}

static inline unsigned int io_put_recv_kbuf(struct io_kiocb *req)
{
        return io_put_kbuf(req, req->sr_msg.kbuf);
}

static int io_recvmsg_prep(struct io_kiocb *req,
                           const struct io_uring_sqe *sqe)
{
        struct io_async_msghdr *async_msg = req->async_data;
        struct io_sr_msg *sr = &req->sr_msg;
        int ret;

        if (unlikely(req->ctx->flags & IORING_SETUP_IOPOLL))
                return -EINVAL;

        sr->msg_flags = READ_ONCE(sqe->msg_flags);
        sr->umsg = u64_to_user_ptr(READ_ONCE(sqe->addr));
        sr->len = READ_ONCE(sqe->len);
        sr->bgid = READ_ONCE(sqe->buf_group);

#ifdef CONFIG_COMPAT
        if (req->ctx->compat)
                sr->msg_flags |= MSG_CMSG_COMPAT;
#endif

        if (!async_msg || !io_op_defs[req->opcode].needs_async_data)
                return 0;
        ret = io_recvmsg_copy_hdr(req, async_msg);
        if (!ret)
                req->flags |= REQ_F_NEED_CLEANUP;
        return ret;
}

static int io_recvmsg(struct io_kiocb *req, bool force_nonblock,
                      struct io_comp_state *cs)
{
        struct io_async_msghdr iomsg, *kmsg;
        struct socket *sock;
        struct io_buffer *kbuf;
        unsigned flags;
        int ret, cflags = 0;

        sock = sock_from_file(req->file);
        if (unlikely(!sock))
                return -ENOTSOCK;

        if (req->async_data) {
                kmsg = req->async_data;
                kmsg->msg.msg_name = &kmsg->addr;
                /* if iov is set, it's allocated already */
                if (!kmsg->iov)
                        kmsg->iov = kmsg->fast_iov;
                kmsg->msg.msg_iter.iov = kmsg->iov;
        } else {
                ret = io_recvmsg_copy_hdr(req, &iomsg);
                if (ret)
                        return ret;
                kmsg = &iomsg;
        }

        if (req->flags & REQ_F_BUFFER_SELECT) {
                kbuf = io_recv_buffer_select(req, !force_nonblock);
                if (IS_ERR(kbuf))
                        return PTR_ERR(kbuf);
                kmsg->fast_iov[0].iov_base = u64_to_user_ptr(kbuf->addr);
                iov_iter_init(&kmsg->msg.msg_iter, READ, kmsg->iov,
                                1, req->sr_msg.len);
        }

        flags = req->sr_msg.msg_flags;
        if (flags & MSG_DONTWAIT)
                req->flags |= REQ_F_NOWAIT;
        else if (force_nonblock)
                flags |= MSG_DONTWAIT;

        ret = __sys_recvmsg_sock(sock, &kmsg->msg, req->sr_msg.umsg,
                                        kmsg->uaddr, flags);
        if (force_nonblock && ret == -EAGAIN)
                return io_setup_async_msg(req, kmsg);
        if (ret == -ERESTARTSYS)
                ret = -EINTR;

        if (req->flags & REQ_F_BUFFER_SELECTED)
                cflags = io_put_recv_kbuf(req);
        if (kmsg->iov != kmsg->fast_iov)
                kfree(kmsg->iov);
        req->flags &= ~REQ_F_NEED_CLEANUP;
        if (ret < 0)
                req_set_fail_links(req);
        __io_req_complete(req, ret, cflags, cs);
        return 0;
}

static int io_recv(struct io_kiocb *req, bool force_nonblock,
                   struct io_comp_state *cs)
{
        struct io_buffer *kbuf;
        struct io_sr_msg *sr = &req->sr_msg;
        struct msghdr msg;
        void __user *buf = sr->buf;
        struct socket *sock;
        struct iovec iov;
        unsigned flags;
        int ret, cflags = 0;

        sock = sock_from_file(req->file);
        if (unlikely(!sock))
                return -ENOTSOCK;

        if (req->flags & REQ_F_BUFFER_SELECT) {
                kbuf = io_recv_buffer_select(req, !force_nonblock);
                if (IS_ERR(kbuf))
                        return PTR_ERR(kbuf);
                buf = u64_to_user_ptr(kbuf->addr);
        }

        ret = import_single_range(READ, buf, sr->len, &iov, &msg.msg_iter);
        if (unlikely(ret))
                goto out_free;

        msg.msg_name = NULL;
        msg.msg_control = NULL;
        msg.msg_controllen = 0;
        msg.msg_namelen = 0;
        msg.msg_iocb = NULL;
        msg.msg_flags = 0;

        flags = req->sr_msg.msg_flags;
        if (flags & MSG_DONTWAIT)
                req->flags |= REQ_F_NOWAIT;
        else if (force_nonblock)
                flags |= MSG_DONTWAIT;

        ret = sock_recvmsg(sock, &msg, flags);
        if (force_nonblock && ret == -EAGAIN)
                return -EAGAIN;
        if (ret == -ERESTARTSYS)
                ret = -EINTR;
out_free:
        if (req->flags & REQ_F_BUFFER_SELECTED)
                cflags = io_put_recv_kbuf(req);
        if (ret < 0)
                req_set_fail_links(req);
        __io_req_complete(req, ret, cflags, cs);
        return 0;
}

static int io_accept_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
{
        struct io_accept *accept = &req->accept;

        if (unlikely(req->ctx->flags & IORING_SETUP_IOPOLL))
                return -EINVAL;
        if (sqe->ioprio || sqe->len || sqe->buf_index)
                return -EINVAL;

        accept->addr = u64_to_user_ptr(READ_ONCE(sqe->addr));
        accept->addr_len = u64_to_user_ptr(READ_ONCE(sqe->addr2));
        accept->flags = READ_ONCE(sqe->accept_flags);
        accept->nofile = rlimit(RLIMIT_NOFILE);
        return 0;
}

static int io_accept(struct io_kiocb *req, bool force_nonblock,
                     struct io_comp_state *cs)
{
        struct io_accept *accept = &req->accept;
        unsigned int file_flags = force_nonblock ? O_NONBLOCK : 0;
        int ret;

        if (req->file->f_flags & O_NONBLOCK)
                req->flags |= REQ_F_NOWAIT;

        ret = __sys_accept4_file(req->file, file_flags, accept->addr,
                                        accept->addr_len, accept->flags,
                                        accept->nofile);
        if (ret == -EAGAIN && force_nonblock)
                return -EAGAIN;
        if (ret < 0) {
                if (ret == -ERESTARTSYS)
                        ret = -EINTR;
                req_set_fail_links(req);
        }
        __io_req_complete(req, ret, 0, cs);
        return 0;
}

static int io_connect_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
{
        struct io_connect *conn = &req->connect;
        struct io_async_connect *io = req->async_data;

        if (unlikely(req->ctx->flags & IORING_SETUP_IOPOLL))
                return -EINVAL;
        if (sqe->ioprio || sqe->len || sqe->buf_index || sqe->rw_flags)
                return -EINVAL;

        conn->addr = u64_to_user_ptr(READ_ONCE(sqe->addr));
        conn->addr_len =  READ_ONCE(sqe->addr2);

        if (!io)
                return 0;

        return move_addr_to_kernel(conn->addr, conn->addr_len,
                                        &io->address);
}

static int io_connect(struct io_kiocb *req, bool force_nonblock,
                      struct io_comp_state *cs)
{
        struct io_async_connect __io, *io;
        unsigned file_flags;
        int ret;

        if (req->async_data) {
                io = req->async_data;
        } else {
                ret = move_addr_to_kernel(req->connect.addr,
                                                req->connect.addr_len,
                                                &__io.address);
                if (ret)
                        goto out;
                io = &__io;
        }

        file_flags = force_nonblock ? O_NONBLOCK : 0;

        ret = __sys_connect_file(req->file, &io->address,
                                        req->connect.addr_len, file_flags);
        if ((ret == -EAGAIN || ret == -EINPROGRESS) && force_nonblock) {
                if (req->async_data)
                        return -EAGAIN;
                if (io_alloc_async_data(req)) {
                        ret = -ENOMEM;
                        goto out;
                }
                io = req->async_data;
                memcpy(req->async_data, &__io, sizeof(__io));
                return -EAGAIN;
        }
        if (ret == -ERESTARTSYS)
                ret = -EINTR;
out:
        if (ret < 0)
                req_set_fail_links(req);
        __io_req_complete(req, ret, 0, cs);
        return 0;
}
#else /* !CONFIG_NET */
static int io_sendmsg_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
{
        return -EOPNOTSUPP;
}

static int io_sendmsg(struct io_kiocb *req, bool force_nonblock,
                      struct io_comp_state *cs)
{
        return -EOPNOTSUPP;
}

static int io_send(struct io_kiocb *req, bool force_nonblock,
                   struct io_comp_state *cs)
{
        return -EOPNOTSUPP;
}

static int io_recvmsg_prep(struct io_kiocb *req,
                           const struct io_uring_sqe *sqe)
{
        return -EOPNOTSUPP;
}

static int io_recvmsg(struct io_kiocb *req, bool force_nonblock,
                      struct io_comp_state *cs)
{
        return -EOPNOTSUPP;
}

static int io_recv(struct io_kiocb *req, bool force_nonblock,
                   struct io_comp_state *cs)
{
        return -EOPNOTSUPP;
}

static int io_accept_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
{
        return -EOPNOTSUPP;
}

static int io_accept(struct io_kiocb *req, bool force_nonblock,
                     struct io_comp_state *cs)
{
        return -EOPNOTSUPP;
}

static int io_connect_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
{
        return -EOPNOTSUPP;
}

static int io_connect(struct io_kiocb *req, bool force_nonblock,
                      struct io_comp_state *cs)
{
        return -EOPNOTSUPP;
}
#endif /* CONFIG_NET */

struct io_poll_table {
        struct poll_table_struct pt;
        struct io_kiocb *req;
        int error;
};

static int __io_async_wake(struct io_kiocb *req, struct io_poll_iocb *poll,
                           __poll_t mask, task_work_func_t func)
{
        int ret;

        /* for instances that support it check for an event match first: */
        if (mask && !(mask & poll->events))
                return 0;

        trace_io_uring_task_add(req->ctx, req->opcode, req->user_data, mask);

        list_del_init(&poll->wait.entry);

        req->result = mask;
        init_task_work(&req->task_work, func);
        percpu_ref_get(&req->ctx->refs);

        /*
         * If this fails, then the task is exiting. When a task exits, the
         * work gets canceled, so just cancel this request as well instead
         * of executing it. We can't safely execute it anyway, as we may not
         * have the needed state needed for it anyway.
         */
        ret = io_req_task_work_add(req);
        if (unlikely(ret)) {
                struct task_struct *tsk;

                WRITE_ONCE(poll->canceled, true);
                tsk = io_wq_get_task(req->ctx->io_wq);
                task_work_add(tsk, &req->task_work, TWA_NONE);
                wake_up_process(tsk);
        }
        return 1;
}

static bool io_poll_rewait(struct io_kiocb *req, struct io_poll_iocb *poll)
        __acquires(&req->ctx->completion_lock)
{
        struct io_ring_ctx *ctx = req->ctx;

        if (!req->result && !READ_ONCE(poll->canceled)) {
                struct poll_table_struct pt = { ._key = poll->events };

                req->result = vfs_poll(req->file, &pt) & poll->events;
        }

        spin_lock_irq(&ctx->completion_lock);
        if (!req->result && !READ_ONCE(poll->canceled)) {
                add_wait_queue(poll->head, &poll->wait);
                return true;
        }

        return false;
}

static struct io_poll_iocb *io_poll_get_double(struct io_kiocb *req)
{
        /* pure poll stashes this in ->async_data, poll driven retry elsewhere */
        if (req->opcode == IORING_OP_POLL_ADD)
                return req->async_data;
        return req->apoll->double_poll;
}

static struct io_poll_iocb *io_poll_get_single(struct io_kiocb *req)
{
        if (req->opcode == IORING_OP_POLL_ADD)
                return &req->poll;
        return &req->apoll->poll;
}

static void io_poll_remove_double(struct io_kiocb *req)
{
        struct io_poll_iocb *poll = io_poll_get_double(req);

        lockdep_assert_held(&req->ctx->completion_lock);

        if (poll && poll->head) {
                struct wait_queue_head *head = poll->head;

                spin_lock(&head->lock);
                list_del_init(&poll->wait.entry);
                if (poll->wait.private)
                        refcount_dec(&req->refs);
                poll->head = NULL;
                spin_unlock(&head->lock);
        }
}

static void io_poll_complete(struct io_kiocb *req, __poll_t mask, int error)
{
        struct io_ring_ctx *ctx = req->ctx;

        io_poll_remove_double(req);
        req->poll.done = true;
        io_cqring_fill_event(req, error ? error : mangle_poll(mask));
        io_commit_cqring(ctx);
}

static void io_poll_task_func(struct callback_head *cb)
{
        struct io_kiocb *req = container_of(cb, struct io_kiocb, task_work);
        struct io_ring_ctx *ctx = req->ctx;
        struct io_kiocb *nxt;

        if (io_poll_rewait(req, &req->poll)) {
                spin_unlock_irq(&ctx->completion_lock);
        } else {
                hash_del(&req->hash_node);
                io_poll_complete(req, req->result, 0);
                spin_unlock_irq(&ctx->completion_lock);

                nxt = io_put_req_find_next(req);
                io_cqring_ev_posted(ctx);
                if (nxt)
                        __io_req_task_submit(nxt);
        }

        percpu_ref_put(&ctx->refs);
}

static int io_poll_double_wake(struct wait_queue_entry *wait, unsigned mode,
                               int sync, void *key)
{
        struct io_kiocb *req = wait->private;
        struct io_poll_iocb *poll = io_poll_get_single(req);
        __poll_t mask = key_to_poll(key);

        /* for instances that support it check for an event match first: */
        if (mask && !(mask & poll->events))
                return 0;

        list_del_init(&wait->entry);

        if (poll && poll->head) {
                bool done;

                spin_lock(&poll->head->lock);
                done = list_empty(&poll->wait.entry);
                if (!done)
                        list_del_init(&poll->wait.entry);
                /* make sure double remove sees this as being gone */
                wait->private = NULL;
                spin_unlock(&poll->head->lock);
                if (!done) {
                        /* use wait func handler, so it matches the rq type */
                        poll->wait.func(&poll->wait, mode, sync, key);
                }
        }
        refcount_dec(&req->refs);
        return 1;
}

static void io_init_poll_iocb(struct io_poll_iocb *poll, __poll_t events,
                              wait_queue_func_t wake_func)
{
        poll->head = NULL;
        poll->done = false;
        poll->canceled = false;
        poll->events = events;
        INIT_LIST_HEAD(&poll->wait.entry);
        init_waitqueue_func_entry(&poll->wait, wake_func);
}

static void __io_queue_proc(struct io_poll_iocb *poll, struct io_poll_table *pt,
                            struct wait_queue_head *head,
                            struct io_poll_iocb **poll_ptr)
{
        struct io_kiocb *req = pt->req;

        /*
         * If poll->head is already set, it's because the file being polled
         * uses multiple waitqueues for poll handling (eg one for read, one
         * for write). Setup a separate io_poll_iocb if this happens.
         */
        if (unlikely(poll->head)) {
                struct io_poll_iocb *poll_one = poll;

                /* already have a 2nd entry, fail a third attempt */
                if (*poll_ptr) {
                        pt->error = -EINVAL;
                        return;
                }
                poll = kmalloc(sizeof(*poll), GFP_ATOMIC);
                if (!poll) {
                        pt->error = -ENOMEM;
                        return;
                }
                io_init_poll_iocb(poll, poll_one->events, io_poll_double_wake);
                refcount_inc(&req->refs);
                poll->wait.private = req;
                *poll_ptr = poll;
        }

        pt->error = 0;
        poll->head = head;

        if (poll->events & EPOLLEXCLUSIVE)
                add_wait_queue_exclusive(head, &poll->wait);
        else
                add_wait_queue(head, &poll->wait);
}

static void io_async_queue_proc(struct file *file, struct wait_queue_head *head,
                               struct poll_table_struct *p)
{
        struct io_poll_table *pt = container_of(p, struct io_poll_table, pt);
        struct async_poll *apoll = pt->req->apoll;

        __io_queue_proc(&apoll->poll, pt, head, &apoll->double_poll);
}

static void io_async_task_func(struct callback_head *cb)
{
        struct io_kiocb *req = container_of(cb, struct io_kiocb, task_work);
        struct async_poll *apoll = req->apoll;
        struct io_ring_ctx *ctx = req->ctx;

        trace_io_uring_task_run(req->ctx, req->opcode, req->user_data);

        if (io_poll_rewait(req, &apoll->poll)) {
                spin_unlock_irq(&ctx->completion_lock);
                percpu_ref_put(&ctx->refs);
                return;
        }

        /* If req is still hashed, it cannot have been canceled. Don't check. */
        if (hash_hashed(&req->hash_node))
                hash_del(&req->hash_node);

        io_poll_remove_double(req);
        spin_unlock_irq(&ctx->completion_lock);

        if (!READ_ONCE(apoll->poll.canceled))
                __io_req_task_submit(req);
        else
                __io_req_task_cancel(req, -ECANCELED);

        percpu_ref_put(&ctx->refs);
        kfree(apoll->double_poll);
        kfree(apoll);
}

static int io_async_wake(struct wait_queue_entry *wait, unsigned mode, int sync,
                        void *key)
{
        struct io_kiocb *req = wait->private;
        struct io_poll_iocb *poll = &req->apoll->poll;

        trace_io_uring_poll_wake(req->ctx, req->opcode, req->user_data,
                                        key_to_poll(key));

        return __io_async_wake(req, poll, key_to_poll(key), io_async_task_func);
}

static void io_poll_req_insert(struct io_kiocb *req)
{
        struct io_ring_ctx *ctx = req->ctx;
        struct hlist_head *list;

        list = &ctx->cancel_hash[hash_long(req->user_data, ctx->cancel_hash_bits)];
        hlist_add_head(&req->hash_node, list);
}

static __poll_t __io_arm_poll_handler(struct io_kiocb *req,
                                      struct io_poll_iocb *poll,
                                      struct io_poll_table *ipt, __poll_t mask,
                                      wait_queue_func_t wake_func)
        __acquires(&ctx->completion_lock)
{
        struct io_ring_ctx *ctx = req->ctx;
        bool cancel = false;

        INIT_HLIST_NODE(&req->hash_node);
        io_init_poll_iocb(poll, mask, wake_func);
        poll->file = req->file;
        poll->wait.private = req;

        ipt->pt._key = mask;
        ipt->req = req;
        ipt->error = -EINVAL;

        mask = vfs_poll(req->file, &ipt->pt) & poll->events;

        spin_lock_irq(&ctx->completion_lock);
        if (likely(poll->head)) {
                spin_lock(&poll->head->lock);
                if (unlikely(list_empty(&poll->wait.entry))) {
                        if (ipt->error)
                                cancel = true;
                        ipt->error = 0;
                        mask = 0;
                }
                if (mask || ipt->error)
                        list_del_init(&poll->wait.entry);
                else if (cancel)
                        WRITE_ONCE(poll->canceled, true);
                else if (!poll->done) /* actually waiting for an event */
                        io_poll_req_insert(req);
                spin_unlock(&poll->head->lock);
        }

        return mask;
}

static bool io_arm_poll_handler(struct io_kiocb *req)
{
        const struct io_op_def *def = &io_op_defs[req->opcode];
        struct io_ring_ctx *ctx = req->ctx;
        struct async_poll *apoll;
        struct io_poll_table ipt;
        __poll_t mask, ret;
        int rw;

        if (!req->file || !file_can_poll(req->file))
                return false;
        if (req->flags & REQ_F_POLLED)
                return false;
        if (def->pollin)
                rw = READ;
        else if (def->pollout)
                rw = WRITE;
        else
                return false;
        /* if we can't nonblock try, then no point in arming a poll handler */
        if (!io_file_supports_async(req->file, rw))
                return false;

        apoll = kmalloc(sizeof(*apoll), GFP_ATOMIC);
        if (unlikely(!apoll))
                return false;
        apoll->double_poll = NULL;

        req->flags |= REQ_F_POLLED;
        req->apoll = apoll;

        mask = 0;
        if (def->pollin)
                mask |= POLLIN | POLLRDNORM;
        if (def->pollout)
                mask |= POLLOUT | POLLWRNORM;

        /* If reading from MSG_ERRQUEUE using recvmsg, ignore POLLIN */
        if ((req->opcode == IORING_OP_RECVMSG) &&
            (req->sr_msg.msg_flags & MSG_ERRQUEUE))
                mask &= ~POLLIN;

        mask |= POLLERR | POLLPRI;

        ipt.pt._qproc = io_async_queue_proc;

        ret = __io_arm_poll_handler(req, &apoll->poll, &ipt, mask,
                                        io_async_wake);
        if (ret || ipt.error) {
                io_poll_remove_double(req);
                spin_unlock_irq(&ctx->completion_lock);
                kfree(apoll->double_poll);
                kfree(apoll);
                return false;
        }
        spin_unlock_irq(&ctx->completion_lock);
        trace_io_uring_poll_arm(ctx, req->opcode, req->user_data, mask,
                                        apoll->poll.events);
        return true;
}

static bool __io_poll_remove_one(struct io_kiocb *req,
                                 struct io_poll_iocb *poll)
{
        bool do_complete = false;

        spin_lock(&poll->head->lock);
        WRITE_ONCE(poll->canceled, true);
        if (!list_empty(&poll->wait.entry)) {
                list_del_init(&poll->wait.entry);
                do_complete = true;
        }
        spin_unlock(&poll->head->lock);
        hash_del(&req->hash_node);
        return do_complete;
}

static bool io_poll_remove_one(struct io_kiocb *req)
{
        bool do_complete;

        io_poll_remove_double(req);

        if (req->opcode == IORING_OP_POLL_ADD) {
                do_complete = __io_poll_remove_one(req, &req->poll);
        } else {
                struct async_poll *apoll = req->apoll;

                /* non-poll requests have submit ref still */
                do_complete = __io_poll_remove_one(req, &apoll->poll);
                if (do_complete) {
                        io_put_req(req);
                        kfree(apoll->double_poll);
                        kfree(apoll);
                }
        }

        if (do_complete) {
                io_cqring_fill_event(req, -ECANCELED);
                io_commit_cqring(req->ctx);
                req_set_fail_links(req);
                io_put_req_deferred(req, 1);
        }

        return do_complete;
}

/*
 * Returns true if we found and killed one or more poll requests
 */
static bool io_poll_remove_all(struct io_ring_ctx *ctx, struct task_struct *tsk,
                               struct files_struct *files)
{
        struct hlist_node *tmp;
        struct io_kiocb *req;
        int posted = 0, i;

        spin_lock_irq(&ctx->completion_lock);
        for (i = 0; i < (1U << ctx->cancel_hash_bits); i++) {
                struct hlist_head *list;

                list = &ctx->cancel_hash[i];
                hlist_for_each_entry_safe(req, tmp, list, hash_node) {
                        if (io_match_task(req, tsk, files))
                                posted += io_poll_remove_one(req);
                }
        }
        spin_unlock_irq(&ctx->completion_lock);

        if (posted)
                io_cqring_ev_posted(ctx);

        return posted != 0;
}

static int io_poll_cancel(struct io_ring_ctx *ctx, __u64 sqe_addr)
{
        struct hlist_head *list;
        struct io_kiocb *req;

        list = &ctx->cancel_hash[hash_long(sqe_addr, ctx->cancel_hash_bits)];
        hlist_for_each_entry(req, list, hash_node) {
                if (sqe_addr != req->user_data)
                        continue;
                if (io_poll_remove_one(req))
                        return 0;
                return -EALREADY;
        }

        return -ENOENT;
}

static int io_poll_remove_prep(struct io_kiocb *req,
                               const struct io_uring_sqe *sqe)
{
        if (unlikely(req->ctx->flags & IORING_SETUP_IOPOLL))
                return -EINVAL;
        if (sqe->ioprio || sqe->off || sqe->len || sqe->buf_index ||
            sqe->poll_events)
                return -EINVAL;

        req->poll_remove.addr = READ_ONCE(sqe->addr);
        return 0;
}

/*
 * Find a running poll command that matches one specified in sqe->addr,
 * and remove it if found.
 */
static int io_poll_remove(struct io_kiocb *req)
{
        struct io_ring_ctx *ctx = req->ctx;
        int ret;

        spin_lock_irq(&ctx->completion_lock);
        ret = io_poll_cancel(ctx, req->poll_remove.addr);
        spin_unlock_irq(&ctx->completion_lock);

        if (ret < 0)
                req_set_fail_links(req);
        io_req_complete(req, ret);
        return 0;
}

static int io_poll_wake(struct wait_queue_entry *wait, unsigned mode, int sync,
                        void *key)
{
        struct io_kiocb *req = wait->private;
        struct io_poll_iocb *poll = &req->poll;

        return __io_async_wake(req, poll, key_to_poll(key), io_poll_task_func);
}

static void io_poll_queue_proc(struct file *file, struct wait_queue_head *head,
                               struct poll_table_struct *p)
{
        struct io_poll_table *pt = container_of(p, struct io_poll_table, pt);

        __io_queue_proc(&pt->req->poll, pt, head, (struct io_poll_iocb **) &pt->req->async_data);
}

static int io_poll_add_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
{
        struct io_poll_iocb *poll = &req->poll;
        u32 events;

        if (unlikely(req->ctx->flags & IORING_SETUP_IOPOLL))
                return -EINVAL;
        if (sqe->addr || sqe->ioprio || sqe->off || sqe->len || sqe->buf_index)
                return -EINVAL;

        events = READ_ONCE(sqe->poll32_events);
#ifdef __BIG_ENDIAN
        events = swahw32(events);
#endif
        poll->events = demangle_poll(events) | EPOLLERR | EPOLLHUP |
                       (events & EPOLLEXCLUSIVE);
        return 0;
}

static int io_poll_add(struct io_kiocb *req)
{
        struct io_poll_iocb *poll = &req->poll;
        struct io_ring_ctx *ctx = req->ctx;
        struct io_poll_table ipt;
        __poll_t mask;

        ipt.pt._qproc = io_poll_queue_proc;

        mask = __io_arm_poll_handler(req, &req->poll, &ipt, poll->events,
                                        io_poll_wake);

        if (mask) { /* no async, we'd stolen it */
                ipt.error = 0;
                io_poll_complete(req, mask, 0);
        }
        spin_unlock_irq(&ctx->completion_lock);

        if (mask) {
                io_cqring_ev_posted(ctx);
                io_put_req(req);
        }
        return ipt.error;
}

static enum hrtimer_restart io_timeout_fn(struct hrtimer *timer)
{
        struct io_timeout_data *data = container_of(timer,
                                                struct io_timeout_data, timer);
        struct io_kiocb *req = data->req;
        struct io_ring_ctx *ctx = req->ctx;
        unsigned long flags;

        spin_lock_irqsave(&ctx->completion_lock, flags);
        list_del_init(&req->timeout.list);
        atomic_set(&req->ctx->cq_timeouts,
                atomic_read(&req->ctx->cq_timeouts) + 1);

        io_cqring_fill_event(req, -ETIME);
        io_commit_cqring(ctx);
        spin_unlock_irqrestore(&ctx->completion_lock, flags);

        io_cqring_ev_posted(ctx);
        req_set_fail_links(req);
        io_put_req(req);
        return HRTIMER_NORESTART;
}

static struct io_kiocb *io_timeout_extract(struct io_ring_ctx *ctx,
                                           __u64 user_data)
{
        struct io_timeout_data *io;
        struct io_kiocb *req;
        int ret = -ENOENT;

        list_for_each_entry(req, &ctx->timeout_list, timeout.list) {
                if (user_data == req->user_data) {
                        ret = 0;
                        break;
                }
        }

        if (ret == -ENOENT)
                return ERR_PTR(ret);

        io = req->async_data;
        ret = hrtimer_try_to_cancel(&io->timer);
        if (ret == -1)
                return ERR_PTR(-EALREADY);
        list_del_init(&req->timeout.list);
        return req;
}

static int io_timeout_cancel(struct io_ring_ctx *ctx, __u64 user_data)
{
        struct io_kiocb *req = io_timeout_extract(ctx, user_data);

        if (IS_ERR(req))
                return PTR_ERR(req);

        req_set_fail_links(req);
        io_cqring_fill_event(req, -ECANCELED);
        io_put_req_deferred(req, 1);
        return 0;
}

static int io_timeout_update(struct io_ring_ctx *ctx, __u64 user_data,
                             struct timespec64 *ts, enum hrtimer_mode mode)
{
        struct io_kiocb *req = io_timeout_extract(ctx, user_data);
        struct io_timeout_data *data;

        if (IS_ERR(req))
                return PTR_ERR(req);

        req->timeout.off = 0; /* noseq */
        data = req->async_data;
        list_add_tail(&req->timeout.list, &ctx->timeout_list);
        hrtimer_init(&data->timer, CLOCK_MONOTONIC, mode);
        data->timer.function = io_timeout_fn;
        hrtimer_start(&data->timer, timespec64_to_ktime(*ts), mode);
        return 0;
}

static int io_timeout_remove_prep(struct io_kiocb *req,
                                  const struct io_uring_sqe *sqe)
{
        struct io_timeout_rem *tr = &req->timeout_rem;

        if (unlikely(req->ctx->flags & IORING_SETUP_IOPOLL))
                return -EINVAL;
        if (unlikely(req->flags & (REQ_F_FIXED_FILE | REQ_F_BUFFER_SELECT)))
                return -EINVAL;
        if (sqe->ioprio || sqe->buf_index || sqe->len)
                return -EINVAL;

        tr->addr = READ_ONCE(sqe->addr);
        tr->flags = READ_ONCE(sqe->timeout_flags);
        if (tr->flags & IORING_TIMEOUT_UPDATE) {
                if (tr->flags & ~(IORING_TIMEOUT_UPDATE|IORING_TIMEOUT_ABS))
                        return -EINVAL;
                if (get_timespec64(&tr->ts, u64_to_user_ptr(sqe->addr2)))
                        return -EFAULT;
        } else if (tr->flags) {
                /* timeout removal doesn't support flags */
                return -EINVAL;
        }

        return 0;
}

/*
 * Remove or update an existing timeout command
 */
static int io_timeout_remove(struct io_kiocb *req)
{
        struct io_timeout_rem *tr = &req->timeout_rem;
        struct io_ring_ctx *ctx = req->ctx;
        int ret;

        spin_lock_irq(&ctx->completion_lock);
        if (req->timeout_rem.flags & IORING_TIMEOUT_UPDATE) {
                enum hrtimer_mode mode = (tr->flags & IORING_TIMEOUT_ABS)
                                        ? HRTIMER_MODE_ABS : HRTIMER_MODE_REL;

                ret = io_timeout_update(ctx, tr->addr, &tr->ts, mode);
        } else {
                ret = io_timeout_cancel(ctx, tr->addr);
        }

        io_cqring_fill_event(req, ret);
        io_commit_cqring(ctx);
        spin_unlock_irq(&ctx->completion_lock);
        io_cqring_ev_posted(ctx);
        if (ret < 0)
                req_set_fail_links(req);
        io_put_req(req);
        return 0;
}

static int io_timeout_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe,
                           bool is_timeout_link)
{
        struct io_timeout_data *data;
        unsigned flags;
        u32 off = READ_ONCE(sqe->off);

        if (unlikely(req->ctx->flags & IORING_SETUP_IOPOLL))
                return -EINVAL;
        if (sqe->ioprio || sqe->buf_index || sqe->len != 1)
                return -EINVAL;
        if (off && is_timeout_link)
                return -EINVAL;
        flags = READ_ONCE(sqe->timeout_flags);
        if (flags & ~IORING_TIMEOUT_ABS)
                return -EINVAL;

        req->timeout.off = off;

        if (!req->async_data && io_alloc_async_data(req))
                return -ENOMEM;

        data = req->async_data;
        data->req = req;

        if (get_timespec64(&data->ts, u64_to_user_ptr(sqe->addr)))
                return -EFAULT;

        if (flags & IORING_TIMEOUT_ABS)
                data->mode = HRTIMER_MODE_ABS;
        else
                data->mode = HRTIMER_MODE_REL;

        hrtimer_init(&data->timer, CLOCK_MONOTONIC, data->mode);
        return 0;
}

static int io_timeout(struct io_kiocb *req)
{
        struct io_ring_ctx *ctx = req->ctx;
        struct io_timeout_data *data = req->async_data;
        struct list_head *entry;
        u32 tail, off = req->timeout.off;

        spin_lock_irq(&ctx->completion_lock);

        /*
         * sqe->off holds how many events that need to occur for this
         * timeout event to be satisfied. If it isn't set, then this is
         * a pure timeout request, sequence isn't used.
         */
        if (io_is_timeout_noseq(req)) {
                entry = ctx->timeout_list.prev;
                goto add;
        }

        tail = ctx->cached_cq_tail - atomic_read(&ctx->cq_timeouts);
        req->timeout.target_seq = tail + off;

        /*
         * Insertion sort, ensuring the first entry in the list is always
         * the one we need first.
         */
        list_for_each_prev(entry, &ctx->timeout_list) {
                struct io_kiocb *nxt = list_entry(entry, struct io_kiocb,
                                                  timeout.list);

                if (io_is_timeout_noseq(nxt))
                        continue;
                /* nxt.seq is behind @tail, otherwise would've been completed */
                if (off >= nxt->timeout.target_seq - tail)
                        break;
        }
add:
        list_add(&req->timeout.list, entry);
        data->timer.function = io_timeout_fn;
        hrtimer_start(&data->timer, timespec64_to_ktime(data->ts), data->mode);
        spin_unlock_irq(&ctx->completion_lock);
        return 0;
}

static bool io_cancel_cb(struct io_wq_work *work, void *data)
{
        struct io_kiocb *req = container_of(work, struct io_kiocb, work);

        return req->user_data == (unsigned long) data;
}

static int io_async_cancel_one(struct io_ring_ctx *ctx, void *sqe_addr)
{
        enum io_wq_cancel cancel_ret;
        int ret = 0;

        cancel_ret = io_wq_cancel_cb(ctx->io_wq, io_cancel_cb, sqe_addr, false);
        switch (cancel_ret) {
        case IO_WQ_CANCEL_OK:
                ret = 0;
                break;
        case IO_WQ_CANCEL_RUNNING:
                ret = -EALREADY;
                break;
        case IO_WQ_CANCEL_NOTFOUND:
                ret = -ENOENT;
                break;
        }

        return ret;
}

static void io_async_find_and_cancel(struct io_ring_ctx *ctx,
                                     struct io_kiocb *req, __u64 sqe_addr,
                                     int success_ret)
{
        unsigned long flags;
        int ret;

        ret = io_async_cancel_one(ctx, (void *) (unsigned long) sqe_addr);
        if (ret != -ENOENT) {
                spin_lock_irqsave(&ctx->completion_lock, flags);
                goto done;
        }

        spin_lock_irqsave(&ctx->completion_lock, flags);
        ret = io_timeout_cancel(ctx, sqe_addr);
        if (ret != -ENOENT)
                goto done;
        ret = io_poll_cancel(ctx, sqe_addr);
done:
        if (!ret)
                ret = success_ret;
        io_cqring_fill_event(req, ret);
        io_commit_cqring(ctx);
        spin_unlock_irqrestore(&ctx->completion_lock, flags);
        io_cqring_ev_posted(ctx);

        if (ret < 0)
                req_set_fail_links(req);
        io_put_req(req);
}

static int io_async_cancel_prep(struct io_kiocb *req,
                                const struct io_uring_sqe *sqe)
{
        if (unlikely(req->ctx->flags & IORING_SETUP_IOPOLL))
                return -EINVAL;
        if (unlikely(req->flags & (REQ_F_FIXED_FILE | REQ_F_BUFFER_SELECT)))
                return -EINVAL;
        if (sqe->ioprio || sqe->off || sqe->len || sqe->cancel_flags)
                return -EINVAL;

        req->cancel.addr = READ_ONCE(sqe->addr);
        return 0;
}

static int io_async_cancel(struct io_kiocb *req)
{
        struct io_ring_ctx *ctx = req->ctx;

        io_async_find_and_cancel(ctx, req, req->cancel.addr, 0);
        return 0;
}

static int io_files_update_prep(struct io_kiocb *req,
                                const struct io_uring_sqe *sqe)
{
        if (unlikely(req->ctx->flags & IORING_SETUP_SQPOLL))
                return -EINVAL;
        if (unlikely(req->flags & (REQ_F_FIXED_FILE | REQ_F_BUFFER_SELECT)))
                return -EINVAL;
        if (sqe->ioprio || sqe->rw_flags)
                return -EINVAL;

        req->files_update.offset = READ_ONCE(sqe->off);
        req->files_update.nr_args = READ_ONCE(sqe->len);
        if (!req->files_update.nr_args)
                return -EINVAL;
        req->files_update.arg = READ_ONCE(sqe->addr);
        return 0;
}

static int io_files_update(struct io_kiocb *req, bool force_nonblock,
                           struct io_comp_state *cs)
{
        struct io_ring_ctx *ctx = req->ctx;
        struct io_uring_files_update up;
        int ret;

        if (force_nonblock)
                return -EAGAIN;

        up.offset = req->files_update.offset;
        up.fds = req->files_update.arg;

        mutex_lock(&ctx->uring_lock);
        ret = __io_sqe_files_update(ctx, &up, req->files_update.nr_args);
        mutex_unlock(&ctx->uring_lock);

        if (ret < 0)
                req_set_fail_links(req);
        __io_req_complete(req, ret, 0, cs);
        return 0;
}

static int io_req_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
{
        switch (req->opcode) {
        case IORING_OP_NOP:
                return 0;
        case IORING_OP_READV:
        case IORING_OP_READ_FIXED:
        case IORING_OP_READ:
                return io_read_prep(req, sqe);
        case IORING_OP_WRITEV:
        case IORING_OP_WRITE_FIXED:
        case IORING_OP_WRITE:
                return io_write_prep(req, sqe);
        case IORING_OP_POLL_ADD:
                return io_poll_add_prep(req, sqe);
        case IORING_OP_POLL_REMOVE:
                return io_poll_remove_prep(req, sqe);
        case IORING_OP_FSYNC:
                return io_prep_fsync(req, sqe);
        case IORING_OP_SYNC_FILE_RANGE:
                return io_prep_sfr(req, sqe);
        case IORING_OP_SENDMSG:
        case IORING_OP_SEND:
                return io_sendmsg_prep(req, sqe);
        case IORING_OP_RECVMSG:
        case IORING_OP_RECV:
                return io_recvmsg_prep(req, sqe);
        case IORING_OP_CONNECT:
                return io_connect_prep(req, sqe);
        case IORING_OP_TIMEOUT:
                return io_timeout_prep(req, sqe, false);
        case IORING_OP_TIMEOUT_REMOVE:
                return io_timeout_remove_prep(req, sqe);
        case IORING_OP_ASYNC_CANCEL:
                return io_async_cancel_prep(req, sqe);
        case IORING_OP_LINK_TIMEOUT:
                return io_timeout_prep(req, sqe, true);
        case IORING_OP_ACCEPT:
                return io_accept_prep(req, sqe);
        case IORING_OP_FALLOCATE:
                return io_fallocate_prep(req, sqe);
        case IORING_OP_OPENAT:
                return io_openat_prep(req, sqe);
        case IORING_OP_CLOSE:
                return io_close_prep(req, sqe);
        case IORING_OP_FILES_UPDATE:
                return io_files_update_prep(req, sqe);
        case IORING_OP_STATX:
                return io_statx_prep(req, sqe);
        case IORING_OP_FADVISE:
                return io_fadvise_prep(req, sqe);
        case IORING_OP_MADVISE:
                return io_madvise_prep(req, sqe);
        case IORING_OP_OPENAT2:
                return io_openat2_prep(req, sqe);
        case IORING_OP_EPOLL_CTL:
                return io_epoll_ctl_prep(req, sqe);
        case IORING_OP_SPLICE:
                return io_splice_prep(req, sqe);
        case IORING_OP_PROVIDE_BUFFERS:
                return io_provide_buffers_prep(req, sqe);
        case IORING_OP_REMOVE_BUFFERS:
                return io_remove_buffers_prep(req, sqe);
        case IORING_OP_TEE:
                return io_tee_prep(req, sqe);
        case IORING_OP_SHUTDOWN:
                return io_shutdown_prep(req, sqe);
        case IORING_OP_RENAMEAT:
                return io_renameat_prep(req, sqe);
        case IORING_OP_UNLINKAT:
                return io_unlinkat_prep(req, sqe);
        }

        printk_once(KERN_WARNING "io_uring: unhandled opcode %d\n",
                        req->opcode);
        return-EINVAL;
}

static int io_req_defer_prep(struct io_kiocb *req,
                             const struct io_uring_sqe *sqe)
{
        if (!sqe)
                return 0;
        if (io_alloc_async_data(req))
                return -EAGAIN;
        return io_req_prep(req, sqe);
}

static u32 io_get_sequence(struct io_kiocb *req)
{
        struct io_kiocb *pos;
        struct io_ring_ctx *ctx = req->ctx;
        u32 total_submitted, nr_reqs = 0;

        io_for_each_link(pos, req)
                nr_reqs++;

        total_submitted = ctx->cached_sq_head - ctx->cached_sq_dropped;
        return total_submitted - nr_reqs;
}

static int io_req_defer(struct io_kiocb *req, const struct io_uring_sqe *sqe)
{
        struct io_ring_ctx *ctx = req->ctx;
        struct io_defer_entry *de;
        int ret;
        u32 seq;

        /* Still need defer if there is pending req in defer list. */
        if (likely(list_empty_careful(&ctx->defer_list) &&
                !(req->flags & REQ_F_IO_DRAIN)))
                return 0;

        seq = io_get_sequence(req);
        /* Still a chance to pass the sequence check */
        if (!req_need_defer(req, seq) && list_empty_careful(&ctx->defer_list))
                return 0;

        if (!req->async_data) {
                ret = io_req_defer_prep(req, sqe);
                if (ret)
                        return ret;
        }
        io_prep_async_link(req);
        de = kmalloc(sizeof(*de), GFP_KERNEL);
        if (!de)
                return -ENOMEM;

        spin_lock_irq(&ctx->completion_lock);
        if (!req_need_defer(req, seq) && list_empty(&ctx->defer_list)) {
                spin_unlock_irq(&ctx->completion_lock);
                kfree(de);
                io_queue_async_work(req);
                return -EIOCBQUEUED;
        }

        trace_io_uring_defer(ctx, req, req->user_data);
        de->req = req;
        de->seq = seq;
        list_add_tail(&de->list, &ctx->defer_list);
        spin_unlock_irq(&ctx->completion_lock);
        return -EIOCBQUEUED;
}

static void io_req_drop_files(struct io_kiocb *req)
{
        struct io_ring_ctx *ctx = req->ctx;
        struct io_uring_task *tctx = req->task->io_uring;
        unsigned long flags;

        put_files_struct(req->work.identity->files);
        put_nsproxy(req->work.identity->nsproxy);
        spin_lock_irqsave(&ctx->inflight_lock, flags);
        list_del(&req->inflight_entry);
        spin_unlock_irqrestore(&ctx->inflight_lock, flags);
        req->flags &= ~REQ_F_INFLIGHT;
        req->work.flags &= ~IO_WQ_WORK_FILES;
        if (atomic_read(&tctx->in_idle))
                wake_up(&tctx->wait);
}

static void __io_clean_op(struct io_kiocb *req)
{
        if (req->flags & REQ_F_BUFFER_SELECTED) {
                switch (req->opcode) {
                case IORING_OP_READV:
                case IORING_OP_READ_FIXED:
                case IORING_OP_READ:
                        kfree((void *)(unsigned long)req->rw.addr);
                        break;
                case IORING_OP_RECVMSG:
                case IORING_OP_RECV:
                        kfree(req->sr_msg.kbuf);
                        break;
                }
                req->flags &= ~REQ_F_BUFFER_SELECTED;
        }

        if (req->flags & REQ_F_NEED_CLEANUP) {
                switch (req->opcode) {
                case IORING_OP_READV:
                case IORING_OP_READ_FIXED:
                case IORING_OP_READ:
                case IORING_OP_WRITEV:
                case IORING_OP_WRITE_FIXED:
                case IORING_OP_WRITE: {
                        struct io_async_rw *io = req->async_data;
                        if (io->free_iovec)
                                kfree(io->free_iovec);
                        break;
                        }
                case IORING_OP_RECVMSG:
                case IORING_OP_SENDMSG: {
                        struct io_async_msghdr *io = req->async_data;
                        if (io->iov != io->fast_iov)
                                kfree(io->iov);
                        break;
                        }
                case IORING_OP_SPLICE:
                case IORING_OP_TEE:
                        io_put_file(req, req->splice.file_in,
                                    (req->splice.flags & SPLICE_F_FD_IN_FIXED));
                        break;
                case IORING_OP_OPENAT:
                case IORING_OP_OPENAT2:
                        if (req->open.filename)
                                putname(req->open.filename);
                        break;
                case IORING_OP_RENAMEAT:
                        putname(req->rename.oldpath);
                        putname(req->rename.newpath);
                        break;
                case IORING_OP_UNLINKAT:
                        putname(req->unlink.filename);
                        break;
                }
                req->flags &= ~REQ_F_NEED_CLEANUP;
        }

        if (req->flags & REQ_F_INFLIGHT)
                io_req_drop_files(req);
}

static int io_issue_sqe(struct io_kiocb *req, bool force_nonblock,
                        struct io_comp_state *cs)
{
        struct io_ring_ctx *ctx = req->ctx;
        int ret;

        switch (req->opcode) {
        case IORING_OP_NOP:
                ret = io_nop(req, cs);
                break;
        case IORING_OP_READV:
        case IORING_OP_READ_FIXED:
        case IORING_OP_READ:
                ret = io_read(req, force_nonblock, cs);
                break;
        case IORING_OP_WRITEV:
        case IORING_OP_WRITE_FIXED:
        case IORING_OP_WRITE:
                ret = io_write(req, force_nonblock, cs);
                break;
        case IORING_OP_FSYNC:
                ret = io_fsync(req, force_nonblock);
                break;
        case IORING_OP_POLL_ADD:
                ret = io_poll_add(req);
                break;
        case IORING_OP_POLL_REMOVE:
                ret = io_poll_remove(req);
                break;
        case IORING_OP_SYNC_FILE_RANGE:
                ret = io_sync_file_range(req, force_nonblock);
                break;
        case IORING_OP_SENDMSG:
                ret = io_sendmsg(req, force_nonblock, cs);
                break;
        case IORING_OP_SEND:
                ret = io_send(req, force_nonblock, cs);
                break;
        case IORING_OP_RECVMSG:
                ret = io_recvmsg(req, force_nonblock, cs);
                break;
        case IORING_OP_RECV:
                ret = io_recv(req, force_nonblock, cs);
                break;
        case IORING_OP_TIMEOUT:
                ret = io_timeout(req);
                break;
        case IORING_OP_TIMEOUT_REMOVE:
                ret = io_timeout_remove(req);
                break;
        case IORING_OP_ACCEPT:
                ret = io_accept(req, force_nonblock, cs);
                break;
        case IORING_OP_CONNECT:
                ret = io_connect(req, force_nonblock, cs);
                break;
        case IORING_OP_ASYNC_CANCEL:
                ret = io_async_cancel(req);
                break;
        case IORING_OP_FALLOCATE:
                ret = io_fallocate(req, force_nonblock);
                break;
        case IORING_OP_OPENAT:
                ret = io_openat(req, force_nonblock);
                break;
        case IORING_OP_CLOSE:
                ret = io_close(req, force_nonblock, cs);
                break;
        case IORING_OP_FILES_UPDATE:
                ret = io_files_update(req, force_nonblock, cs);
                break;
        case IORING_OP_STATX:
                ret = io_statx(req, force_nonblock);
                break;
        case IORING_OP_FADVISE:
                ret = io_fadvise(req, force_nonblock);
                break;
        case IORING_OP_MADVISE:
                ret = io_madvise(req, force_nonblock);
                break;
        case IORING_OP_OPENAT2:
                ret = io_openat2(req, force_nonblock);
                break;
        case IORING_OP_EPOLL_CTL:
                ret = io_epoll_ctl(req, force_nonblock, cs);
                break;
        case IORING_OP_SPLICE:
                ret = io_splice(req, force_nonblock);
                break;
        case IORING_OP_PROVIDE_BUFFERS:
                ret = io_provide_buffers(req, force_nonblock, cs);
                break;
        case IORING_OP_REMOVE_BUFFERS:
                ret = io_remove_buffers(req, force_nonblock, cs);
                break;
        case IORING_OP_TEE:
                ret = io_tee(req, force_nonblock);
                break;
        case IORING_OP_SHUTDOWN:
                ret = io_shutdown(req, force_nonblock);
                break;
        case IORING_OP_RENAMEAT:
                ret = io_renameat(req, force_nonblock);
                break;
        case IORING_OP_UNLINKAT:
                ret = io_unlinkat(req, force_nonblock);
                break;
        default:
                ret = -EINVAL;
                break;
        }

        if (ret)
                return ret;

        /* If the op doesn't have a file, we're not polling for it */
        if ((ctx->flags & IORING_SETUP_IOPOLL) && req->file) {
                const bool in_async = io_wq_current_is_worker();

                /* workqueue context doesn't hold uring_lock, grab it now */
                if (in_async)
                        mutex_lock(&ctx->uring_lock);

                io_iopoll_req_issued(req, in_async);

                if (in_async)
                        mutex_unlock(&ctx->uring_lock);
        }

        return 0;
}

static struct io_wq_work *io_wq_submit_work(struct io_wq_work *work)
{
        struct io_kiocb *req = container_of(work, struct io_kiocb, work);
        struct io_kiocb *timeout;
        int ret = 0;

        timeout = io_prep_linked_timeout(req);
        if (timeout)
                io_queue_linked_timeout(timeout);

        /* if NO_CANCEL is set, we must still run the work */
        if ((work->flags & (IO_WQ_WORK_CANCEL|IO_WQ_WORK_NO_CANCEL)) ==
                                IO_WQ_WORK_CANCEL) {
                ret = -ECANCELED;
        }

        if (!ret) {
                do {
                        ret = io_issue_sqe(req, false, NULL);
                        /*
                         * We can get EAGAIN for polled IO even though we're
                         * forcing a sync submission from here, since we can't
                         * wait for request slots on the block side.
                         */
                        if (ret != -EAGAIN)
                                break;
                        cond_resched();
                } while (1);
        }

        if (ret) {
                struct io_ring_ctx *lock_ctx = NULL;

                if (req->ctx->flags & IORING_SETUP_IOPOLL)
                        lock_ctx = req->ctx;

                /*
                 * io_iopoll_complete() does not hold completion_lock to
                 * complete polled io, so here for polled io, we can not call
                 * io_req_complete() directly, otherwise there maybe concurrent
                 * access to cqring, defer_list, etc, which is not safe. Given
                 * that io_iopoll_complete() is always called under uring_lock,
                 * so here for polled io, we also get uring_lock to complete
                 * it.
                 */
                if (lock_ctx)
                        mutex_lock(&lock_ctx->uring_lock);

                req_set_fail_links(req);
                io_req_complete(req, ret);

                if (lock_ctx)
                        mutex_unlock(&lock_ctx->uring_lock);
        }

        return io_steal_work(req);
}

static inline struct file *io_file_from_index(struct io_ring_ctx *ctx,
                                              int index)
{
        struct fixed_file_table *table;

        table = &ctx->file_data->table[index >> IORING_FILE_TABLE_SHIFT];
        return table->files[index & IORING_FILE_TABLE_MASK];
}

static struct file *io_file_get(struct io_submit_state *state,
                                struct io_kiocb *req, int fd, bool fixed)
{
        struct io_ring_ctx *ctx = req->ctx;
        struct file *file;

        if (fixed) {
                if (unlikely((unsigned int)fd >= ctx->nr_user_files))
                        return NULL;
                fd = array_index_nospec(fd, ctx->nr_user_files);
                file = io_file_from_index(ctx, fd);
                io_set_resource_node(req);
        } else {
                trace_io_uring_file_get(ctx, fd);
                file = __io_file_get(state, fd);
        }

        return file;
}

static enum hrtimer_restart io_link_timeout_fn(struct hrtimer *timer)
{
        struct io_timeout_data *data = container_of(timer,
                                                struct io_timeout_data, timer);
        struct io_kiocb *prev, *req = data->req;
        struct io_ring_ctx *ctx = req->ctx;
        unsigned long flags;

        spin_lock_irqsave(&ctx->completion_lock, flags);
        prev = req->timeout.head;
        req->timeout.head = NULL;

        /*
         * We don't expect the list to be empty, that will only happen if we
         * race with the completion of the linked work.
         */
        if (prev && refcount_inc_not_zero(&prev->refs))
                io_remove_next_linked(prev);
        else
                prev = NULL;
        spin_unlock_irqrestore(&ctx->completion_lock, flags);

        if (prev) {
                req_set_fail_links(prev);
                io_async_find_and_cancel(ctx, req, prev->user_data, -ETIME);
                io_put_req(prev);
        } else {
                io_req_complete(req, -ETIME);
        }
        return HRTIMER_NORESTART;
}

static void __io_queue_linked_timeout(struct io_kiocb *req)
{
        /*
         * If the back reference is NULL, then our linked request finished
         * before we got a chance to setup the timer
         */
        if (req->timeout.head) {
                struct io_timeout_data *data = req->async_data;

                data->timer.function = io_link_timeout_fn;
                hrtimer_start(&data->timer, timespec64_to_ktime(data->ts),
                                data->mode);
        }
}

static void io_queue_linked_timeout(struct io_kiocb *req)
{
        struct io_ring_ctx *ctx = req->ctx;

        spin_lock_irq(&ctx->completion_lock);
        __io_queue_linked_timeout(req);
        spin_unlock_irq(&ctx->completion_lock);

        /* drop submission reference */
        io_put_req(req);
}

static struct io_kiocb *io_prep_linked_timeout(struct io_kiocb *req)
{
        struct io_kiocb *nxt = req->link;

        if (!nxt || (req->flags & REQ_F_LINK_TIMEOUT) ||
            nxt->opcode != IORING_OP_LINK_TIMEOUT)
                return NULL;

        nxt->timeout.head = req;
        nxt->flags |= REQ_F_LTIMEOUT_ACTIVE;
        req->flags |= REQ_F_LINK_TIMEOUT;
        return nxt;
}

static void __io_queue_sqe(struct io_kiocb *req, struct io_comp_state *cs)
{
        struct io_kiocb *linked_timeout;
        const struct cred *old_creds = NULL;
        int ret;

again:
        linked_timeout = io_prep_linked_timeout(req);

        if ((req->flags & REQ_F_WORK_INITIALIZED) &&
            (req->work.flags & IO_WQ_WORK_CREDS) &&
            req->work.identity->creds != current_cred()) {
                if (old_creds)
                        revert_creds(old_creds);
                if (old_creds == req->work.identity->creds)
                        old_creds = NULL; /* restored original creds */
                else
                        old_creds = override_creds(req->work.identity->creds);
        }

        ret = io_issue_sqe(req, true, cs);

        /*
         * We async punt it if the file wasn't marked NOWAIT, or if the file
         * doesn't support non-blocking read/write attempts
         */
        if (ret == -EAGAIN && !(req->flags & REQ_F_NOWAIT)) {
                if (!io_arm_poll_handler(req)) {
                        /*
                         * Queued up for async execution, worker will release
                         * submit reference when the iocb is actually submitted.
                         */
                        io_queue_async_work(req);
                }

                if (linked_timeout)
                        io_queue_linked_timeout(linked_timeout);
        } else if (likely(!ret)) {
                /* drop submission reference */
                req = io_put_req_find_next(req);
                if (linked_timeout)
                        io_queue_linked_timeout(linked_timeout);

                if (req) {
                        if (!(req->flags & REQ_F_FORCE_ASYNC))
                                goto again;
                        io_queue_async_work(req);
                }
        } else {
                /* un-prep timeout, so it'll be killed as any other linked */
                req->flags &= ~REQ_F_LINK_TIMEOUT;
                req_set_fail_links(req);
                io_put_req(req);
                io_req_complete(req, ret);
        }

        if (old_creds)
                revert_creds(old_creds);
}

static void io_queue_sqe(struct io_kiocb *req, const struct io_uring_sqe *sqe,
                         struct io_comp_state *cs)
{
        int ret;

        ret = io_req_defer(req, sqe);
        if (ret) {
                if (ret != -EIOCBQUEUED) {
fail_req:
                        req_set_fail_links(req);
                        io_put_req(req);
                        io_req_complete(req, ret);
                }
        } else if (req->flags & REQ_F_FORCE_ASYNC) {
                if (!req->async_data) {
                        ret = io_req_defer_prep(req, sqe);
                        if (unlikely(ret))
                                goto fail_req;
                }
                io_queue_async_work(req);
        } else {
                if (sqe) {
                        ret = io_req_prep(req, sqe);
                        if (unlikely(ret))
                                goto fail_req;
                }
                __io_queue_sqe(req, cs);
        }
}

static inline void io_queue_link_head(struct io_kiocb *req,
                                      struct io_comp_state *cs)
{
        if (unlikely(req->flags & REQ_F_FAIL_LINK)) {
                io_put_req(req);
                io_req_complete(req, -ECANCELED);
        } else
                io_queue_sqe(req, NULL, cs);
}

struct io_submit_link {
        struct io_kiocb *head;
        struct io_kiocb *last;
};

static int io_submit_sqe(struct io_kiocb *req, const struct io_uring_sqe *sqe,
                         struct io_submit_link *link, struct io_comp_state *cs)
{
        struct io_ring_ctx *ctx = req->ctx;
        int ret;

        /*
         * If we already have a head request, queue this one for async
         * submittal once the head completes. If we don't have a head but
         * IOSQE_IO_LINK is set in the sqe, start a new head. This one will be
         * submitted sync once the chain is complete. If none of those
         * conditions are true (normal request), then just queue it.
         */
        if (link->head) {
                struct io_kiocb *head = link->head;

                /*
                 * Taking sequential execution of a link, draining both sides
                 * of the link also fullfils IOSQE_IO_DRAIN semantics for all
                 * requests in the link. So, it drains the head and the
                 * next after the link request. The last one is done via
                 * drain_next flag to persist the effect across calls.
                 */
                if (req->flags & REQ_F_IO_DRAIN) {
                        head->flags |= REQ_F_IO_DRAIN;
                        ctx->drain_next = 1;
                }
                ret = io_req_defer_prep(req, sqe);
                if (unlikely(ret)) {
                        /* fail even hard links since we don't submit */
                        head->flags |= REQ_F_FAIL_LINK;
                        return ret;
                }
                trace_io_uring_link(ctx, req, head);
                link->last->link = req;
                link->last = req;

                /* last request of a link, enqueue the link */
                if (!(req->flags & (REQ_F_LINK | REQ_F_HARDLINK))) {
                        io_queue_link_head(head, cs);
                        link->head = NULL;
                }
        } else {
                if (unlikely(ctx->drain_next)) {
                        req->flags |= REQ_F_IO_DRAIN;
                        ctx->drain_next = 0;
                }
                if (req->flags & (REQ_F_LINK | REQ_F_HARDLINK)) {
                        ret = io_req_defer_prep(req, sqe);
                        if (unlikely(ret))
                                req->flags |= REQ_F_FAIL_LINK;
                        link->head = req;
                        link->last = req;
                } else {
                        io_queue_sqe(req, sqe, cs);
                }
        }

        return 0;
}

/*
 * Batched submission is done, ensure local IO is flushed out.
 */
static void io_submit_state_end(struct io_submit_state *state)
{
        if (!list_empty(&state->comp.list))
                io_submit_flush_completions(&state->comp);
        if (state->plug_started)
                blk_finish_plug(&state->plug);
        io_state_file_put(state);
        if (state->free_reqs)
                kmem_cache_free_bulk(req_cachep, state->free_reqs, state->reqs);
}

/*
 * Start submission side cache.
 */
static void io_submit_state_start(struct io_submit_state *state,
                                  struct io_ring_ctx *ctx, unsigned int max_ios)
{
        state->plug_started = false;
        state->comp.nr = 0;
        INIT_LIST_HEAD(&state->comp.list);
        state->comp.ctx = ctx;
        state->free_reqs = 0;
        state->file_refs = 0;
        state->ios_left = max_ios;
}

static void io_commit_sqring(struct io_ring_ctx *ctx)
{
        struct io_rings *rings = ctx->rings;

        /*
         * Ensure any loads from the SQEs are done at this point,
         * since once we write the new head, the application could
         * write new data to them.
         */
        smp_store_release(&rings->sq.head, ctx->cached_sq_head);
}

/*
 * Fetch an sqe, if one is available. Note that sqe_ptr will point to memory
 * that is mapped by userspace. This means that care needs to be taken to
 * ensure that reads are stable, as we cannot rely on userspace always
 * being a good citizen. If members of the sqe are validated and then later
 * used, it's important that those reads are done through READ_ONCE() to
 * prevent a re-load down the line.
 */
static const struct io_uring_sqe *io_get_sqe(struct io_ring_ctx *ctx)
{
        u32 *sq_array = ctx->sq_array;
        unsigned head;

        /*
         * The cached sq head (or cq tail) serves two purposes:
         *
         * 1) allows us to batch the cost of updating the user visible
         *    head updates.
         * 2) allows the kernel side to track the head on its own, even
         *    though the application is the one updating it.
         */
        head = READ_ONCE(sq_array[ctx->cached_sq_head & ctx->sq_mask]);
        if (likely(head < ctx->sq_entries))
                return &ctx->sq_sqes[head];

        /* drop invalid entries */
        ctx->cached_sq_dropped++;
        WRITE_ONCE(ctx->rings->sq_dropped, ctx->cached_sq_dropped);
        return NULL;
}

static inline void io_consume_sqe(struct io_ring_ctx *ctx)
{
        ctx->cached_sq_head++;
}

/*
 * Check SQE restrictions (opcode and flags).
 *
 * Returns 'true' if SQE is allowed, 'false' otherwise.
 */
static inline bool io_check_restriction(struct io_ring_ctx *ctx,
                                        struct io_kiocb *req,
                                        unsigned int sqe_flags)
{
        if (!ctx->restricted)
                return true;

        if (!test_bit(req->opcode, ctx->restrictions.sqe_op))
                return false;

        if ((sqe_flags & ctx->restrictions.sqe_flags_required) !=
            ctx->restrictions.sqe_flags_required)
                return false;

        if (sqe_flags & ~(ctx->restrictions.sqe_flags_allowed |
                          ctx->restrictions.sqe_flags_required))
                return false;

        return true;
}

#define SQE_VALID_FLAGS (IOSQE_FIXED_FILE|IOSQE_IO_DRAIN|IOSQE_IO_LINK| \
                                IOSQE_IO_HARDLINK | IOSQE_ASYNC | \
                                IOSQE_BUFFER_SELECT)

static int io_init_req(struct io_ring_ctx *ctx, struct io_kiocb *req,
                       const struct io_uring_sqe *sqe,
                       struct io_submit_state *state)
{
        unsigned int sqe_flags;
        int id, ret;

        req->opcode = READ_ONCE(sqe->opcode);
        req->user_data = READ_ONCE(sqe->user_data);
        req->async_data = NULL;
        req->file = NULL;
        req->ctx = ctx;
        req->flags = 0;
        req->link = NULL;
        req->fixed_file_refs = NULL;
        /* one is dropped after submission, the other at completion */
        refcount_set(&req->refs, 2);
        req->task = current;
        req->result = 0;

        if (unlikely(req->opcode >= IORING_OP_LAST))
                return -EINVAL;

        if (unlikely(io_sq_thread_acquire_mm_files(ctx, req)))
                return -EFAULT;

        sqe_flags = READ_ONCE(sqe->flags);
        /* enforce forwards compatibility on users */
        if (unlikely(sqe_flags & ~SQE_VALID_FLAGS))
                return -EINVAL;

        if (unlikely(!io_check_restriction(ctx, req, sqe_flags)))
                return -EACCES;

        if ((sqe_flags & IOSQE_BUFFER_SELECT) &&
            !io_op_defs[req->opcode].buffer_select)
                return -EOPNOTSUPP;

        id = READ_ONCE(sqe->personality);
        if (id) {
                struct io_identity *iod;

                iod = idr_find(&ctx->personality_idr, id);
                if (unlikely(!iod))
                        return -EINVAL;
                refcount_inc(&iod->count);

                __io_req_init_async(req);
                get_cred(iod->creds);
                req->work.identity = iod;
                req->work.flags |= IO_WQ_WORK_CREDS;
        }

        /* same numerical values with corresponding REQ_F_*, safe to copy */
        req->flags |= sqe_flags;

        /*
         * Plug now if we have more than 1 IO left after this, and the target
         * is potentially a read/write to block based storage.
         */
        if (!state->plug_started && state->ios_left > 1 &&
            io_op_defs[req->opcode].plug) {
                blk_start_plug(&state->plug);
                state->plug_started = true;
        }

        ret = 0;
        if (io_op_defs[req->opcode].needs_file) {
                bool fixed = req->flags & REQ_F_FIXED_FILE;

                req->file = io_file_get(state, req, READ_ONCE(sqe->fd), fixed);
                if (unlikely(!req->file &&
                    !io_op_defs[req->opcode].needs_file_no_error))
                        ret = -EBADF;
        }

        state->ios_left--;
        return ret;
}

static int io_submit_sqes(struct io_ring_ctx *ctx, unsigned int nr)
{
        struct io_submit_state state;
        struct io_submit_link link;
        int i, submitted = 0;

        /* if we have a backlog and couldn't flush it all, return BUSY */
        if (test_bit(0, &ctx->sq_check_overflow)) {
                if (!__io_cqring_overflow_flush(ctx, false, NULL, NULL))
                        return -EBUSY;
        }

        /* make sure SQ entry isn't read before tail */
        nr = min3(nr, ctx->sq_entries, io_sqring_entries(ctx));

        if (!percpu_ref_tryget_many(&ctx->refs, nr))
                return -EAGAIN;

        percpu_counter_add(&current->io_uring->inflight, nr);
        refcount_add(nr, &current->usage);

        io_submit_state_start(&state, ctx, nr);
        link.head = NULL;

        for (i = 0; i < nr; i++) {
                const struct io_uring_sqe *sqe;
                struct io_kiocb *req;
                int err;

                sqe = io_get_sqe(ctx);
                if (unlikely(!sqe)) {
                        io_consume_sqe(ctx);
                        break;
                }
                req = io_alloc_req(ctx, &state);
                if (unlikely(!req)) {
                        if (!submitted)
                                submitted = -EAGAIN;
                        break;
                }
                io_consume_sqe(ctx);
                /* will complete beyond this point, count as submitted */
                submitted++;

                err = io_init_req(ctx, req, sqe, &state);
                if (unlikely(err)) {
fail_req:
                        io_put_req(req);
                        io_req_complete(req, err);
                        break;
                }

                trace_io_uring_submit_sqe(ctx, req->opcode, req->user_data,
                                                true, io_async_submit(ctx));
                err = io_submit_sqe(req, sqe, &link, &state.comp);
                if (err)
                        goto fail_req;
        }

        if (unlikely(submitted != nr)) {
                int ref_used = (submitted == -EAGAIN) ? 0 : submitted;
                struct io_uring_task *tctx = current->io_uring;
                int unused = nr - ref_used;

                percpu_ref_put_many(&ctx->refs, unused);
                percpu_counter_sub(&tctx->inflight, unused);
                put_task_struct_many(current, unused);
        }
        if (link.head)
                io_queue_link_head(link.head, &state.comp);
        io_submit_state_end(&state);

         /* Commit SQ ring head once we've consumed and submitted all SQEs */
        io_commit_sqring(ctx);

        return submitted;
}

static inline void io_ring_set_wakeup_flag(struct io_ring_ctx *ctx)
{
        /* Tell userspace we may need a wakeup call */
        spin_lock_irq(&ctx->completion_lock);
        ctx->rings->sq_flags |= IORING_SQ_NEED_WAKEUP;
        spin_unlock_irq(&ctx->completion_lock);
}

static inline void io_ring_clear_wakeup_flag(struct io_ring_ctx *ctx)
{
        spin_lock_irq(&ctx->completion_lock);
        ctx->rings->sq_flags &= ~IORING_SQ_NEED_WAKEUP;
        spin_unlock_irq(&ctx->completion_lock);
}

static int __io_sq_thread(struct io_ring_ctx *ctx, bool cap_entries)
{
        unsigned int to_submit;
        int ret = 0;

        to_submit = io_sqring_entries(ctx);
        /* if we're handling multiple rings, cap submit size for fairness */
        if (cap_entries && to_submit > 8)
                to_submit = 8;

        if (!list_empty(&ctx->iopoll_list) || to_submit) {
                unsigned nr_events = 0;

                mutex_lock(&ctx->uring_lock);
                if (!list_empty(&ctx->iopoll_list))
                        io_do_iopoll(ctx, &nr_events, 0);

                if (to_submit && likely(!percpu_ref_is_dying(&ctx->refs)))
                        ret = io_submit_sqes(ctx, to_submit);
                mutex_unlock(&ctx->uring_lock);
        }

        if (!io_sqring_full(ctx) && wq_has_sleeper(&ctx->sqo_sq_wait))
                wake_up(&ctx->sqo_sq_wait);

        return ret;
}

static void io_sqd_update_thread_idle(struct io_sq_data *sqd)
{
        struct io_ring_ctx *ctx;
        unsigned sq_thread_idle = 0;

        list_for_each_entry(ctx, &sqd->ctx_list, sqd_list) {
                if (sq_thread_idle < ctx->sq_thread_idle)
                        sq_thread_idle = ctx->sq_thread_idle;
        }

        sqd->sq_thread_idle = sq_thread_idle;
}

static void io_sqd_init_new(struct io_sq_data *sqd)
{
        struct io_ring_ctx *ctx;

        while (!list_empty(&sqd->ctx_new_list)) {
                ctx = list_first_entry(&sqd->ctx_new_list, struct io_ring_ctx, sqd_list);
                list_move_tail(&ctx->sqd_list, &sqd->ctx_list);
                complete(&ctx->sq_thread_comp);
        }

        io_sqd_update_thread_idle(sqd);
}

static int io_sq_thread(void *data)
{
        struct cgroup_subsys_state *cur_css = NULL;
        struct files_struct *old_files = current->files;
        struct nsproxy *old_nsproxy = current->nsproxy;
        const struct cred *old_cred = NULL;
        struct io_sq_data *sqd = data;
        struct io_ring_ctx *ctx;
        unsigned long timeout = 0;
        DEFINE_WAIT(wait);

        task_lock(current);
        current->files = NULL;
        current->nsproxy = NULL;
        task_unlock(current);

        while (!kthread_should_stop()) {
                int ret;
                bool cap_entries, sqt_spin, needs_sched;

                /*
                 * Any changes to the sqd lists are synchronized through the
                 * kthread parking. This synchronizes the thread vs users,
                 * the users are synchronized on the sqd->ctx_lock.
                 */
                if (kthread_should_park()) {
                        kthread_parkme();
                        /*
                         * When sq thread is unparked, in case the previous park operation
                         * comes from io_put_sq_data(), which means that sq thread is going
                         * to be stopped, so here needs to have a check.
                         */
                        if (kthread_should_stop())
                                break;
                }

                if (unlikely(!list_empty(&sqd->ctx_new_list))) {
                        io_sqd_init_new(sqd);
                        timeout = jiffies + sqd->sq_thread_idle;
                }

                sqt_spin = false;
                cap_entries = !list_is_singular(&sqd->ctx_list);
                list_for_each_entry(ctx, &sqd->ctx_list, sqd_list) {
                        if (current->cred != ctx->creds) {
                                if (old_cred)
                                        revert_creds(old_cred);
                                old_cred = override_creds(ctx->creds);
                        }
                        io_sq_thread_associate_blkcg(ctx, &cur_css);
#ifdef CONFIG_AUDIT
                        current->loginuid = ctx->loginuid;
                        current->sessionid = ctx->sessionid;
#endif

                        ret = __io_sq_thread(ctx, cap_entries);
                        if (!sqt_spin && (ret > 0 || !list_empty(&ctx->iopoll_list)))
                                sqt_spin = true;

                        io_sq_thread_drop_mm_files();
                }

                if (sqt_spin || !time_after(jiffies, timeout)) {
                        io_run_task_work();
                        cond_resched();
                        if (sqt_spin)
                                timeout = jiffies + sqd->sq_thread_idle;
                        continue;
                }

                if (kthread_should_park())
                        continue;

                needs_sched = true;
                prepare_to_wait(&sqd->wait, &wait, TASK_INTERRUPTIBLE);
                list_for_each_entry(ctx, &sqd->ctx_list, sqd_list) {
                        if ((ctx->flags & IORING_SETUP_IOPOLL) &&
                            !list_empty_careful(&ctx->iopoll_list)) {
                                needs_sched = false;
                                break;
                        }
                        if (io_sqring_entries(ctx)) {
                                needs_sched = false;
                                break;
                        }
                }

                if (needs_sched) {
                        list_for_each_entry(ctx, &sqd->ctx_list, sqd_list)
                                io_ring_set_wakeup_flag(ctx);

                        schedule();
                        list_for_each_entry(ctx, &sqd->ctx_list, sqd_list)
                                io_ring_clear_wakeup_flag(ctx);
                }

                finish_wait(&sqd->wait, &wait);
                timeout = jiffies + sqd->sq_thread_idle;
        }

        io_run_task_work();

        if (cur_css)
                io_sq_thread_unassociate_blkcg();
        if (old_cred)
                revert_creds(old_cred);

        task_lock(current);
        current->files = old_files;
        current->nsproxy = old_nsproxy;
        task_unlock(current);

        kthread_parkme();

        return 0;
}

struct io_wait_queue {
        struct wait_queue_entry wq;
        struct io_ring_ctx *ctx;
        unsigned to_wait;
        unsigned nr_timeouts;
};

static inline bool io_should_wake(struct io_wait_queue *iowq)
{
        struct io_ring_ctx *ctx = iowq->ctx;

        /*
         * Wake up if we have enough events, or if a timeout occurred since we
         * started waiting. For timeouts, we always want to return to userspace,
         * regardless of event count.
         */
        return io_cqring_events(ctx) >= iowq->to_wait ||
                        atomic_read(&ctx->cq_timeouts) != iowq->nr_timeouts;
}

static int io_wake_function(struct wait_queue_entry *curr, unsigned int mode,
                            int wake_flags, void *key)
{
        struct io_wait_queue *iowq = container_of(curr, struct io_wait_queue,
                                                        wq);

        /*
         * Cannot safely flush overflowed CQEs from here, ensure we wake up
         * the task, and the next invocation will do it.
         */
        if (io_should_wake(iowq) || test_bit(0, &iowq->ctx->cq_check_overflow))
                return autoremove_wake_function(curr, mode, wake_flags, key);
        return -1;
}

static int io_run_task_work_sig(void)
{
        if (io_run_task_work())
                return 1;
        if (!signal_pending(current))
                return 0;
        if (test_tsk_thread_flag(current, TIF_NOTIFY_SIGNAL))
                return -ERESTARTSYS;
        return -EINTR;
}

/*
 * Wait until events become available, if we don't already have some. The
 * application must reap them itself, as they reside on the shared cq ring.
 */
static int io_cqring_wait(struct io_ring_ctx *ctx, int min_events,
                          const sigset_t __user *sig, size_t sigsz,
                          struct __kernel_timespec __user *uts)
{
        struct io_wait_queue iowq = {
                .wq = {
                        .private        = current,
                        .func           = io_wake_function,
                        .entry          = LIST_HEAD_INIT(iowq.wq.entry),
                },
                .ctx            = ctx,
                .to_wait        = min_events,
        };
        struct io_rings *rings = ctx->rings;
        struct timespec64 ts;
        signed long timeout = 0;
        int ret = 0;

        do {
                io_cqring_overflow_flush(ctx, false, NULL, NULL);
                if (io_cqring_events(ctx) >= min_events)
                        return 0;
                if (!io_run_task_work())
                        break;
        } while (1);

        if (sig) {
#ifdef CONFIG_COMPAT
                if (in_compat_syscall())
                        ret = set_compat_user_sigmask((const compat_sigset_t __user *)sig,
                                                      sigsz);
                else
#endif
                        ret = set_user_sigmask(sig, sigsz);

                if (ret)
                        return ret;
        }

        if (uts) {
                if (get_timespec64(&ts, uts))
                        return -EFAULT;
                timeout = timespec64_to_jiffies(&ts);
        }

        iowq.nr_timeouts = atomic_read(&ctx->cq_timeouts);
        trace_io_uring_cqring_wait(ctx, min_events);
        do {
                io_cqring_overflow_flush(ctx, false, NULL, NULL);
                prepare_to_wait_exclusive(&ctx->wait, &iowq.wq,
                                                TASK_INTERRUPTIBLE);
                /* make sure we run task_work before checking for signals */
                ret = io_run_task_work_sig();
                if (ret > 0)
                        continue;
                else if (ret < 0)
                        break;
                if (io_should_wake(&iowq))
                        break;
                if (test_bit(0, &ctx->cq_check_overflow))
                        continue;
                if (uts) {
                        timeout = schedule_timeout(timeout);
                        if (timeout == 0) {
                                ret = -ETIME;
                                break;
                        }
                } else {
                        schedule();
                }
        } while (1);
        finish_wait(&ctx->wait, &iowq.wq);

        restore_saved_sigmask_unless(ret == -EINTR);

        return READ_ONCE(rings->cq.head) == READ_ONCE(rings->cq.tail) ? ret : 0;
}

static void __io_sqe_files_unregister(struct io_ring_ctx *ctx)
{
#if defined(CONFIG_UNIX)
        if (ctx->ring_sock) {
                struct sock *sock = ctx->ring_sock->sk;
                struct sk_buff *skb;

                while ((skb = skb_dequeue(&sock->sk_receive_queue)) != NULL)
                        kfree_skb(skb);
        }
#else
        int i;

        for (i = 0; i < ctx->nr_user_files; i++) {
                struct file *file;

                file = io_file_from_index(ctx, i);
                if (file)
                        fput(file);
        }
#endif
}

static void io_file_ref_kill(struct percpu_ref *ref)
{
        struct fixed_file_data *data;

        data = container_of(ref, struct fixed_file_data, refs);
        complete(&data->done);
}

static void io_sqe_files_set_node(struct fixed_file_data *file_data,
                                  struct fixed_file_ref_node *ref_node)
{
        spin_lock_bh(&file_data->lock);
        file_data->node = ref_node;
        list_add_tail(&ref_node->node, &file_data->ref_list);
        spin_unlock_bh(&file_data->lock);
        percpu_ref_get(&file_data->refs);
}

static int io_sqe_files_unregister(struct io_ring_ctx *ctx)
{
        struct fixed_file_data *data = ctx->file_data;
        struct fixed_file_ref_node *backup_node, *ref_node = NULL;
        unsigned nr_tables, i;
        int ret;

        if (!data)
                return -ENXIO;
        backup_node = alloc_fixed_file_ref_node(ctx);
        if (!backup_node)
                return -ENOMEM;

        spin_lock_bh(&data->lock);
        ref_node = data->node;
        spin_unlock_bh(&data->lock);
        if (ref_node)
                percpu_ref_kill(&ref_node->refs);

        percpu_ref_kill(&data->refs);

        /* wait for all refs nodes to complete */
        flush_delayed_work(&ctx->file_put_work);
        do {
                ret = wait_for_completion_interruptible(&data->done);
                if (!ret)
                        break;
                ret = io_run_task_work_sig();
                if (ret < 0) {
                        percpu_ref_resurrect(&data->refs);
                        reinit_completion(&data->done);
                        io_sqe_files_set_node(data, backup_node);
                        return ret;
                }
        } while (1);

        __io_sqe_files_unregister(ctx);
        nr_tables = DIV_ROUND_UP(ctx->nr_user_files, IORING_MAX_FILES_TABLE);
        for (i = 0; i < nr_tables; i++)
                kfree(data->table[i].files);
        kfree(data->table);
        percpu_ref_exit(&data->refs);
        kfree(data);
        ctx->file_data = NULL;
        ctx->nr_user_files = 0;
        destroy_fixed_file_ref_node(backup_node);
        return 0;
}

static void io_put_sq_data(struct io_sq_data *sqd)
{
        if (refcount_dec_and_test(&sqd->refs)) {
                /*
                 * The park is a bit of a work-around, without it we get
                 * warning spews on shutdown with SQPOLL set and affinity
                 * set to a single CPU.
                 */
                if (sqd->thread) {
                        kthread_park(sqd->thread);
                        kthread_stop(sqd->thread);
                }

                kfree(sqd);
        }
}

static struct io_sq_data *io_attach_sq_data(struct io_uring_params *p)
{
        struct io_ring_ctx *ctx_attach;
        struct io_sq_data *sqd;
        struct fd f;

        f = fdget(p->wq_fd);
        if (!f.file)
                return ERR_PTR(-ENXIO);
        if (f.file->f_op != &io_uring_fops) {
                fdput(f);
                return ERR_PTR(-EINVAL);
        }

        ctx_attach = f.file->private_data;
        sqd = ctx_attach->sq_data;
        if (!sqd) {
                fdput(f);
                return ERR_PTR(-EINVAL);
        }

        refcount_inc(&sqd->refs);
        fdput(f);
        return sqd;
}

static struct io_sq_data *io_get_sq_data(struct io_uring_params *p)
{
        struct io_sq_data *sqd;

        if (p->flags & IORING_SETUP_ATTACH_WQ)
                return io_attach_sq_data(p);

        sqd = kzalloc(sizeof(*sqd), GFP_KERNEL);
        if (!sqd)
                return ERR_PTR(-ENOMEM);

        refcount_set(&sqd->refs, 1);
        INIT_LIST_HEAD(&sqd->ctx_list);
        INIT_LIST_HEAD(&sqd->ctx_new_list);
        mutex_init(&sqd->ctx_lock);
        mutex_init(&sqd->lock);
        init_waitqueue_head(&sqd->wait);
        return sqd;
}

static void io_sq_thread_unpark(struct io_sq_data *sqd)
        __releases(&sqd->lock)
{
        if (!sqd->thread)
                return;
        kthread_unpark(sqd->thread);
        mutex_unlock(&sqd->lock);
}

static void io_sq_thread_park(struct io_sq_data *sqd)
        __acquires(&sqd->lock)
{
        if (!sqd->thread)
                return;
        mutex_lock(&sqd->lock);
        kthread_park(sqd->thread);
}

static void io_sq_thread_stop(struct io_ring_ctx *ctx)
{
        struct io_sq_data *sqd = ctx->sq_data;

        if (sqd) {
                if (sqd->thread) {
                        /*
                         * We may arrive here from the error branch in
                         * io_sq_offload_create() where the kthread is created
                         * without being waked up, thus wake it up now to make
                         * sure the wait will complete.
                         */
                        wake_up_process(sqd->thread);
                        wait_for_completion(&ctx->sq_thread_comp);

                        io_sq_thread_park(sqd);
                }

                mutex_lock(&sqd->ctx_lock);
                list_del(&ctx->sqd_list);
                io_sqd_update_thread_idle(sqd);
                mutex_unlock(&sqd->ctx_lock);

                if (sqd->thread)
                        io_sq_thread_unpark(sqd);

                io_put_sq_data(sqd);
                ctx->sq_data = NULL;
        }
}

static void io_finish_async(struct io_ring_ctx *ctx)
{
        io_sq_thread_stop(ctx);

        if (ctx->io_wq) {
                io_wq_destroy(ctx->io_wq);
                ctx->io_wq = NULL;
        }
}

#if defined(CONFIG_UNIX)
/*
 * Ensure the UNIX gc is aware of our file set, so we are certain that
 * the io_uring can be safely unregistered on process exit, even if we have
 * loops in the file referencing.
 */
static int __io_sqe_files_scm(struct io_ring_ctx *ctx, int nr, int offset)
{
        struct sock *sk = ctx->ring_sock->sk;
        struct scm_fp_list *fpl;
        struct sk_buff *skb;
        int i, nr_files;

        fpl = kzalloc(sizeof(*fpl), GFP_KERNEL);
        if (!fpl)
                return -ENOMEM;

        skb = alloc_skb(0, GFP_KERNEL);
        if (!skb) {
                kfree(fpl);
                return -ENOMEM;
        }

        skb->sk = sk;

        nr_files = 0;
        fpl->user = get_uid(ctx->user);
        for (i = 0; i < nr; i++) {
                struct file *file = io_file_from_index(ctx, i + offset);

                if (!file)
                        continue;
                fpl->fp[nr_files] = get_file(file);
                unix_inflight(fpl->user, fpl->fp[nr_files]);
                nr_files++;
        }

        if (nr_files) {
                fpl->max = SCM_MAX_FD;
                fpl->count = nr_files;
                UNIXCB(skb).fp = fpl;
                skb->destructor = unix_destruct_scm;
                refcount_add(skb->truesize, &sk->sk_wmem_alloc);
                skb_queue_head(&sk->sk_receive_queue, skb);

                for (i = 0; i < nr_files; i++)
                        fput(fpl->fp[i]);
        } else {
                kfree_skb(skb);
                kfree(fpl);
        }

        return 0;
}

/*
 * If UNIX sockets are enabled, fd passing can cause a reference cycle which
 * causes regular reference counting to break down. We rely on the UNIX
 * garbage collection to take care of this problem for us.
 */
static int io_sqe_files_scm(struct io_ring_ctx *ctx)
{
        unsigned left, total;
        int ret = 0;

        total = 0;
        left = ctx->nr_user_files;
        while (left) {
                unsigned this_files = min_t(unsigned, left, SCM_MAX_FD);

                ret = __io_sqe_files_scm(ctx, this_files, total);
                if (ret)
                        break;
                left -= this_files;
                total += this_files;
        }

        if (!ret)
                return 0;

        while (total < ctx->nr_user_files) {
                struct file *file = io_file_from_index(ctx, total);

                if (file)
                        fput(file);
                total++;
        }

        return ret;
}
#else
static int io_sqe_files_scm(struct io_ring_ctx *ctx)
{
        return 0;
}
#endif

static int io_sqe_alloc_file_tables(struct fixed_file_data *file_data,
                                    unsigned nr_tables, unsigned nr_files)
{
        int i;

        for (i = 0; i < nr_tables; i++) {
                struct fixed_file_table *table = &file_data->table[i];
                unsigned this_files;

                this_files = min(nr_files, IORING_MAX_FILES_TABLE);
                table->files = kcalloc(this_files, sizeof(struct file *),
                                        GFP_KERNEL);
                if (!table->files)
                        break;
                nr_files -= this_files;
        }

        if (i == nr_tables)
                return 0;

        for (i = 0; i < nr_tables; i++) {
                struct fixed_file_table *table = &file_data->table[i];
                kfree(table->files);
        }
        return 1;
}

static void io_ring_file_put(struct io_ring_ctx *ctx, struct file *file)
{
#if defined(CONFIG_UNIX)
        struct sock *sock = ctx->ring_sock->sk;
        struct sk_buff_head list, *head = &sock->sk_receive_queue;
        struct sk_buff *skb;
        int i;

        __skb_queue_head_init(&list);

        /*
         * Find the skb that holds this file in its SCM_RIGHTS. When found,
         * remove this entry and rearrange the file array.
         */
        skb = skb_dequeue(head);
        while (skb) {
                struct scm_fp_list *fp;

                fp = UNIXCB(skb).fp;
                for (i = 0; i < fp->count; i++) {
                        int left;

                        if (fp->fp[i] != file)
                                continue;

                        unix_notinflight(fp->user, fp->fp[i]);
                        left = fp->count - 1 - i;
                        if (left) {
                                memmove(&fp->fp[i], &fp->fp[i + 1],
                                                left * sizeof(struct file *));
                        }
                        fp->count--;
                        if (!fp->count) {
                                kfree_skb(skb);
                                skb = NULL;
                        } else {
                                __skb_queue_tail(&list, skb);
                        }
                        fput(file);
                        file = NULL;
                        break;
                }

                if (!file)
                        break;

                __skb_queue_tail(&list, skb);

                skb = skb_dequeue(head);
        }

        if (skb_peek(&list)) {
                spin_lock_irq(&head->lock);
                while ((skb = __skb_dequeue(&list)) != NULL)
                        __skb_queue_tail(head, skb);
                spin_unlock_irq(&head->lock);
        }
#else
        fput(file);
#endif
}

struct io_file_put {
        struct list_head list;
        struct file *file;
};

static void __io_file_put_work(struct fixed_file_ref_node *ref_node)
{
        struct fixed_file_data *file_data = ref_node->file_data;
        struct io_ring_ctx *ctx = file_data->ctx;
        struct io_file_put *pfile, *tmp;

        list_for_each_entry_safe(pfile, tmp, &ref_node->file_list, list) {
                list_del(&pfile->list);
                io_ring_file_put(ctx, pfile->file);
                kfree(pfile);
        }

        percpu_ref_exit(&ref_node->refs);
        kfree(ref_node);
        percpu_ref_put(&file_data->refs);
}

static void io_file_put_work(struct work_struct *work)
{
        struct io_ring_ctx *ctx;
        struct llist_node *node;

        ctx = container_of(work, struct io_ring_ctx, file_put_work.work);
        node = llist_del_all(&ctx->file_put_llist);

        while (node) {
                struct fixed_file_ref_node *ref_node;
                struct llist_node *next = node->next;

                ref_node = llist_entry(node, struct fixed_file_ref_node, llist);
                __io_file_put_work(ref_node);
                node = next;
        }
}

static void io_file_data_ref_zero(struct percpu_ref *ref)
{
        struct fixed_file_ref_node *ref_node;
        struct fixed_file_data *data;
        struct io_ring_ctx *ctx;
        bool first_add = false;
        int delay = HZ;

        ref_node = container_of(ref, struct fixed_file_ref_node, refs);
        data = ref_node->file_data;
        ctx = data->ctx;

        spin_lock_bh(&data->lock);
        ref_node->done = true;

        while (!list_empty(&data->ref_list)) {
                ref_node = list_first_entry(&data->ref_list,
                                        struct fixed_file_ref_node, node);
                /* recycle ref nodes in order */
                if (!ref_node->done)
                        break;
                list_del(&ref_node->node);
                first_add |= llist_add(&ref_node->llist, &ctx->file_put_llist);
        }
        spin_unlock_bh(&data->lock);

        if (percpu_ref_is_dying(&data->refs))
                delay = 0;

        if (!delay)
                mod_delayed_work(system_wq, &ctx->file_put_work, 0);
        else if (first_add)
                queue_delayed_work(system_wq, &ctx->file_put_work, delay);
}

static struct fixed_file_ref_node *alloc_fixed_file_ref_node(
                        struct io_ring_ctx *ctx)
{
        struct fixed_file_ref_node *ref_node;

        ref_node = kzalloc(sizeof(*ref_node), GFP_KERNEL);
        if (!ref_node)
                return NULL;

        if (percpu_ref_init(&ref_node->refs, io_file_data_ref_zero,
                            0, GFP_KERNEL)) {
                kfree(ref_node);
                return NULL;
        }
        INIT_LIST_HEAD(&ref_node->node);
        INIT_LIST_HEAD(&ref_node->file_list);
        ref_node->file_data = ctx->file_data;
        ref_node->done = false;
        return ref_node;
}

static void destroy_fixed_file_ref_node(struct fixed_file_ref_node *ref_node)
{
        percpu_ref_exit(&ref_node->refs);
        kfree(ref_node);
}

static int io_sqe_files_register(struct io_ring_ctx *ctx, void __user *arg,
                                 unsigned nr_args)
{
        __s32 __user *fds = (__s32 __user *) arg;
        unsigned nr_tables, i;
        struct file *file;
        int fd, ret = -ENOMEM;
        struct fixed_file_ref_node *ref_node;
        struct fixed_file_data *file_data;

        if (ctx->file_data)
                return -EBUSY;
        if (!nr_args)
                return -EINVAL;
        if (nr_args > IORING_MAX_FIXED_FILES)
                return -EMFILE;

        file_data = kzalloc(sizeof(*ctx->file_data), GFP_KERNEL);
        if (!file_data)
                return -ENOMEM;
        file_data->ctx = ctx;
        init_completion(&file_data->done);
        INIT_LIST_HEAD(&file_data->ref_list);
        spin_lock_init(&file_data->lock);

        nr_tables = DIV_ROUND_UP(nr_args, IORING_MAX_FILES_TABLE);
        file_data->table = kcalloc(nr_tables, sizeof(*file_data->table),
                                   GFP_KERNEL);
        if (!file_data->table)
                goto out_free;

        if (percpu_ref_init(&file_data->refs, io_file_ref_kill,
                                PERCPU_REF_ALLOW_REINIT, GFP_KERNEL))
                goto out_free;

        if (io_sqe_alloc_file_tables(file_data, nr_tables, nr_args))
                goto out_ref;
        ctx->file_data = file_data;

        for (i = 0; i < nr_args; i++, ctx->nr_user_files++) {
                struct fixed_file_table *table;
                unsigned index;

                if (copy_from_user(&fd, &fds[i], sizeof(fd))) {
                        ret = -EFAULT;
                        goto out_fput;
                }
                /* allow sparse sets */
                if (fd == -1)
                        continue;

                file = fget(fd);
                ret = -EBADF;
                if (!file)
                        goto out_fput;

                /*
                 * Don't allow io_uring instances to be registered. If UNIX
                 * isn't enabled, then this causes a reference cycle and this
                 * instance can never get freed. If UNIX is enabled we'll
                 * handle it just fine, but there's still no point in allowing
                 * a ring fd as it doesn't support regular read/write anyway.
                 */
                if (file->f_op == &io_uring_fops) {
                        fput(file);
                        goto out_fput;
                }
                table = &file_data->table[i >> IORING_FILE_TABLE_SHIFT];
                index = i & IORING_FILE_TABLE_MASK;
                table->files[index] = file;
        }

        ret = io_sqe_files_scm(ctx);
        if (ret) {
                io_sqe_files_unregister(ctx);
                return ret;
        }

        ref_node = alloc_fixed_file_ref_node(ctx);
        if (!ref_node) {
                io_sqe_files_unregister(ctx);
                return -ENOMEM;
        }

        io_sqe_files_set_node(file_data, ref_node);
        return ret;
out_fput:
        for (i = 0; i < ctx->nr_user_files; i++) {
                file = io_file_from_index(ctx, i);
                if (file)
                        fput(file);
        }
        for (i = 0; i < nr_tables; i++)
                kfree(file_data->table[i].files);
        ctx->nr_user_files = 0;
out_ref:
        percpu_ref_exit(&file_data->refs);
out_free:
        kfree(file_data->table);
        kfree(file_data);
        ctx->file_data = NULL;
        return ret;
}

static int io_sqe_file_register(struct io_ring_ctx *ctx, struct file *file,
                                int index)
{
#if defined(CONFIG_UNIX)
        struct sock *sock = ctx->ring_sock->sk;
        struct sk_buff_head *head = &sock->sk_receive_queue;
        struct sk_buff *skb;

        /*
         * See if we can merge this file into an existing skb SCM_RIGHTS
         * file set. If there's no room, fall back to allocating a new skb
         * and filling it in.
         */
        spin_lock_irq(&head->lock);
        skb = skb_peek(head);
        if (skb) {
                struct scm_fp_list *fpl = UNIXCB(skb).fp;

                if (fpl->count < SCM_MAX_FD) {
                        __skb_unlink(skb, head);
                        spin_unlock_irq(&head->lock);
                        fpl->fp[fpl->count] = get_file(file);
                        unix_inflight(fpl->user, fpl->fp[fpl->count]);
                        fpl->count++;
                        spin_lock_irq(&head->lock);
                        __skb_queue_head(head, skb);
                } else {
                        skb = NULL;
                }
        }
        spin_unlock_irq(&head->lock);

        if (skb) {
                fput(file);
                return 0;
        }

        return __io_sqe_files_scm(ctx, 1, index);
#else
        return 0;
#endif
}

static int io_queue_file_removal(struct fixed_file_data *data,
                                 struct file *file)
{
        struct io_file_put *pfile;
        struct fixed_file_ref_node *ref_node = data->node;

        pfile = kzalloc(sizeof(*pfile), GFP_KERNEL);
        if (!pfile)
                return -ENOMEM;

        pfile->file = file;
        list_add(&pfile->list, &ref_node->file_list);

        return 0;
}

static int __io_sqe_files_update(struct io_ring_ctx *ctx,
                                 struct io_uring_files_update *up,
                                 unsigned nr_args)
{
        struct fixed_file_data *data = ctx->file_data;
        struct fixed_file_ref_node *ref_node;
        struct file *file;
        __s32 __user *fds;
        int fd, i, err;
        __u32 done;
        bool needs_switch = false;

        if (check_add_overflow(up->offset, nr_args, &done))
                return -EOVERFLOW;
        if (done > ctx->nr_user_files)
                return -EINVAL;

        ref_node = alloc_fixed_file_ref_node(ctx);
        if (!ref_node)
                return -ENOMEM;

        done = 0;
        fds = u64_to_user_ptr(up->fds);
        while (nr_args) {
                struct fixed_file_table *table;
                unsigned index;

                err = 0;
                if (copy_from_user(&fd, &fds[done], sizeof(fd))) {
                        err = -EFAULT;
                        break;
                }
                i = array_index_nospec(up->offset, ctx->nr_user_files);
                table = &ctx->file_data->table[i >> IORING_FILE_TABLE_SHIFT];
                index = i & IORING_FILE_TABLE_MASK;
                if (table->files[index]) {
                        file = table->files[index];
                        err = io_queue_file_removal(data, file);
                        if (err)
                                break;
                        table->files[index] = NULL;
                        needs_switch = true;
                }
                if (fd != -1) {
                        file = fget(fd);
                        if (!file) {
                                err = -EBADF;
                                break;
                        }
                        /*
                         * Don't allow io_uring instances to be registered. If
                         * UNIX isn't enabled, then this causes a reference
                         * cycle and this instance can never get freed. If UNIX
                         * is enabled we'll handle it just fine, but there's
                         * still no point in allowing a ring fd as it doesn't
                         * support regular read/write anyway.
                         */
                        if (file->f_op == &io_uring_fops) {
                                fput(file);
                                err = -EBADF;
                                break;
                        }
                        table->files[index] = file;
                        err = io_sqe_file_register(ctx, file, i);
                        if (err) {
                                table->files[index] = NULL;
                                fput(file);
                                break;
                        }
                }
                nr_args--;
                done++;
                up->offset++;
        }

        if (needs_switch) {
                percpu_ref_kill(&data->node->refs);
                io_sqe_files_set_node(data, ref_node);
        } else
                destroy_fixed_file_ref_node(ref_node);

        return done ? done : err;
}

static int io_sqe_files_update(struct io_ring_ctx *ctx, void __user *arg,
                               unsigned nr_args)
{
        struct io_uring_files_update up;

        if (!ctx->file_data)
                return -ENXIO;
        if (!nr_args)
                return -EINVAL;
        if (copy_from_user(&up, arg, sizeof(up)))
                return -EFAULT;
        if (up.resv)
                return -EINVAL;

        return __io_sqe_files_update(ctx, &up, nr_args);
}

static void io_free_work(struct io_wq_work *work)
{
        struct io_kiocb *req = container_of(work, struct io_kiocb, work);

        /* Consider that io_steal_work() relies on this ref */
        io_put_req(req);
}

static int io_init_wq_offload(struct io_ring_ctx *ctx,
                              struct io_uring_params *p)
{
        struct io_wq_data data;
        struct fd f;
        struct io_ring_ctx *ctx_attach;
        unsigned int concurrency;
        int ret = 0;

        data.user = ctx->user;
        data.free_work = io_free_work;
        data.do_work = io_wq_submit_work;

        if (!(p->flags & IORING_SETUP_ATTACH_WQ)) {
                /* Do QD, or 4 * CPUS, whatever is smallest */
                concurrency = min(ctx->sq_entries, 4 * num_online_cpus());

                ctx->io_wq = io_wq_create(concurrency, &data);
                if (IS_ERR(ctx->io_wq)) {
                        ret = PTR_ERR(ctx->io_wq);
                        ctx->io_wq = NULL;
                }
                return ret;
        }

        f = fdget(p->wq_fd);
        if (!f.file)
                return -EBADF;

        if (f.file->f_op != &io_uring_fops) {
                ret = -EINVAL;
                goto out_fput;
        }

        ctx_attach = f.file->private_data;
        /* @io_wq is protected by holding the fd */
        if (!io_wq_get(ctx_attach->io_wq, &data)) {
                ret = -EINVAL;
                goto out_fput;
        }

        ctx->io_wq = ctx_attach->io_wq;
out_fput:
        fdput(f);
        return ret;
}

static int io_uring_alloc_task_context(struct task_struct *task)
{
        struct io_uring_task *tctx;
        int ret;

        tctx = kmalloc(sizeof(*tctx), GFP_KERNEL);
        if (unlikely(!tctx))
                return -ENOMEM;

        ret = percpu_counter_init(&tctx->inflight, 0, GFP_KERNEL);
        if (unlikely(ret)) {
                kfree(tctx);
                return ret;
        }

        xa_init(&tctx->xa);
        init_waitqueue_head(&tctx->wait);
        tctx->last = NULL;
        atomic_set(&tctx->in_idle, 0);
        tctx->sqpoll = false;
        io_init_identity(&tctx->__identity);
        tctx->identity = &tctx->__identity;
        task->io_uring = tctx;
        return 0;
}

void __io_uring_free(struct task_struct *tsk)
{
        struct io_uring_task *tctx = tsk->io_uring;

        WARN_ON_ONCE(!xa_empty(&tctx->xa));
        WARN_ON_ONCE(refcount_read(&tctx->identity->count) != 1);
        if (tctx->identity != &tctx->__identity)
                kfree(tctx->identity);
        percpu_counter_destroy(&tctx->inflight);
        kfree(tctx);
        tsk->io_uring = NULL;
}

static int io_sq_offload_create(struct io_ring_ctx *ctx,
                                struct io_uring_params *p)
{
        int ret;

        if (ctx->flags & IORING_SETUP_SQPOLL) {
                struct io_sq_data *sqd;

                ret = -EPERM;
                if (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_NICE))
                        goto err;

                sqd = io_get_sq_data(p);
                if (IS_ERR(sqd)) {
                        ret = PTR_ERR(sqd);
                        goto err;
                }

                ctx->sq_data = sqd;
                io_sq_thread_park(sqd);
                mutex_lock(&sqd->ctx_lock);
                list_add(&ctx->sqd_list, &sqd->ctx_new_list);
                mutex_unlock(&sqd->ctx_lock);
                io_sq_thread_unpark(sqd);

                ctx->sq_thread_idle = msecs_to_jiffies(p->sq_thread_idle);
                if (!ctx->sq_thread_idle)
                        ctx->sq_thread_idle = HZ;

                if (sqd->thread)
                        goto done;

                if (p->flags & IORING_SETUP_SQ_AFF) {
                        int cpu = p->sq_thread_cpu;

                        ret = -EINVAL;
                        if (cpu >= nr_cpu_ids)
                                goto err;
                        if (!cpu_online(cpu))
                                goto err;

                        sqd->thread = kthread_create_on_cpu(io_sq_thread, sqd,
                                                        cpu, "io_uring-sq");
                } else {
                        sqd->thread = kthread_create(io_sq_thread, sqd,
                                                        "io_uring-sq");
                }
                if (IS_ERR(sqd->thread)) {
                        ret = PTR_ERR(sqd->thread);
                        sqd->thread = NULL;
                        goto err;
                }
                ret = io_uring_alloc_task_context(sqd->thread);
                if (ret)
                        goto err;
        } else if (p->flags & IORING_SETUP_SQ_AFF) {
                /* Can't have SQ_AFF without SQPOLL */
                ret = -EINVAL;
                goto err;
        }

done:
        ret = io_init_wq_offload(ctx, p);
        if (ret)
                goto err;

        return 0;
err:
        io_finish_async(ctx);
        return ret;
}

static void io_sq_offload_start(struct io_ring_ctx *ctx)
{
        struct io_sq_data *sqd = ctx->sq_data;

        if ((ctx->flags & IORING_SETUP_SQPOLL) && sqd->thread)
                wake_up_process(sqd->thread);
}

static inline void __io_unaccount_mem(struct user_struct *user,
                                      unsigned long nr_pages)
{
        atomic_long_sub(nr_pages, &user->locked_vm);
}

static inline int __io_account_mem(struct user_struct *user,
                                   unsigned long nr_pages)
{
        unsigned long page_limit, cur_pages, new_pages;

        /* Don't allow more pages than we can safely lock */
        page_limit = rlimit(RLIMIT_MEMLOCK) >> PAGE_SHIFT;

        do {
                cur_pages = atomic_long_read(&user->locked_vm);
                new_pages = cur_pages + nr_pages;
                if (new_pages > page_limit)
                        return -ENOMEM;
        } while (atomic_long_cmpxchg(&user->locked_vm, cur_pages,
                                        new_pages) != cur_pages);

        return 0;
}

static void io_unaccount_mem(struct io_ring_ctx *ctx, unsigned long nr_pages,
                             enum io_mem_account acct)
{
        if (ctx->limit_mem)
                __io_unaccount_mem(ctx->user, nr_pages);

        if (ctx->mm_account) {
                if (acct == ACCT_LOCKED) {
                        mmap_write_lock(ctx->mm_account);
                        ctx->mm_account->locked_vm -= nr_pages;
                        mmap_write_unlock(ctx->mm_account);
                }else if (acct == ACCT_PINNED) {
                        atomic64_sub(nr_pages, &ctx->mm_account->pinned_vm);
                }
        }
}

static int io_account_mem(struct io_ring_ctx *ctx, unsigned long nr_pages,
                          enum io_mem_account acct)
{
        int ret;

        if (ctx->limit_mem) {
                ret = __io_account_mem(ctx->user, nr_pages);
                if (ret)
                        return ret;
        }

        if (ctx->mm_account) {
                if (acct == ACCT_LOCKED) {
                        mmap_write_lock(ctx->mm_account);
                        ctx->mm_account->locked_vm += nr_pages;
                        mmap_write_unlock(ctx->mm_account);
                } else if (acct == ACCT_PINNED) {
                        atomic64_add(nr_pages, &ctx->mm_account->pinned_vm);
                }
        }

        return 0;
}

static void io_mem_free(void *ptr)
{
        struct page *page;

        if (!ptr)
                return;

        page = virt_to_head_page(ptr);
        if (put_page_testzero(page))
                free_compound_page(page);
}

static void *io_mem_alloc(size_t size)
{
        gfp_t gfp_flags = GFP_KERNEL | __GFP_ZERO | __GFP_NOWARN | __GFP_COMP |
                                __GFP_NORETRY;

        return (void *) __get_free_pages(gfp_flags, get_order(size));
}

static unsigned long rings_size(unsigned sq_entries, unsigned cq_entries,
                                size_t *sq_offset)
{
        struct io_rings *rings;
        size_t off, sq_array_size;

        off = struct_size(rings, cqes, cq_entries);
        if (off == SIZE_MAX)
                return SIZE_MAX;

#ifdef CONFIG_SMP
        off = ALIGN(off, SMP_CACHE_BYTES);
        if (off == 0)
                return SIZE_MAX;
#endif

        if (sq_offset)
                *sq_offset = off;

        sq_array_size = array_size(sizeof(u32), sq_entries);
        if (sq_array_size == SIZE_MAX)
                return SIZE_MAX;

        if (check_add_overflow(off, sq_array_size, &off))
                return SIZE_MAX;

        return off;
}

static unsigned long ring_pages(unsigned sq_entries, unsigned cq_entries)
{
        size_t pages;

        pages = (size_t)1 << get_order(
                rings_size(sq_entries, cq_entries, NULL));
        pages += (size_t)1 << get_order(
                array_size(sizeof(struct io_uring_sqe), sq_entries));

        return pages;
}

static int io_sqe_buffer_unregister(struct io_ring_ctx *ctx)
{
        int i, j;

        if (!ctx->user_bufs)
                return -ENXIO;

        for (i = 0; i < ctx->nr_user_bufs; i++) {
                struct io_mapped_ubuf *imu = &ctx->user_bufs[i];

                for (j = 0; j < imu->nr_bvecs; j++)
                        unpin_user_page(imu->bvec[j].bv_page);

                if (imu->acct_pages)
                        io_unaccount_mem(ctx, imu->acct_pages, ACCT_PINNED);
                kvfree(imu->bvec);
                imu->nr_bvecs = 0;
        }

        kfree(ctx->user_bufs);
        ctx->user_bufs = NULL;
        ctx->nr_user_bufs = 0;
        return 0;
}

static int io_copy_iov(struct io_ring_ctx *ctx, struct iovec *dst,
                       void __user *arg, unsigned index)
{
        struct iovec __user *src;

#ifdef CONFIG_COMPAT
        if (ctx->compat) {
                struct compat_iovec __user *ciovs;
                struct compat_iovec ciov;

                ciovs = (struct compat_iovec __user *) arg;
                if (copy_from_user(&ciov, &ciovs[index], sizeof(ciov)))
                        return -EFAULT;

                dst->iov_base = u64_to_user_ptr((u64)ciov.iov_base);
                dst->iov_len = ciov.iov_len;
                return 0;
        }
#endif
        src = (struct iovec __user *) arg;
        if (copy_from_user(dst, &src[index], sizeof(*dst)))
                return -EFAULT;
        return 0;
}

/*
 * Not super efficient, but this is just a registration time. And we do cache
 * the last compound head, so generally we'll only do a full search if we don't
 * match that one.
 *
 * We check if the given compound head page has already been accounted, to
 * avoid double accounting it. This allows us to account the full size of the
 * page, not just the constituent pages of a huge page.
 */
static bool headpage_already_acct(struct io_ring_ctx *ctx, struct page **pages,
                                  int nr_pages, struct page *hpage)
{
        int i, j;

        /* check current page array */
        for (i = 0; i < nr_pages; i++) {
                if (!PageCompound(pages[i]))
                        continue;
                if (compound_head(pages[i]) == hpage)
                        return true;
        }

        /* check previously registered pages */
        for (i = 0; i < ctx->nr_user_bufs; i++) {
                struct io_mapped_ubuf *imu = &ctx->user_bufs[i];

                for (j = 0; j < imu->nr_bvecs; j++) {
                        if (!PageCompound(imu->bvec[j].bv_page))
                                continue;
                        if (compound_head(imu->bvec[j].bv_page) == hpage)
                                return true;
                }
        }

        return false;
}

static int io_buffer_account_pin(struct io_ring_ctx *ctx, struct page **pages,
                                 int nr_pages, struct io_mapped_ubuf *imu,
                                 struct page **last_hpage)
{
        int i, ret;

        for (i = 0; i < nr_pages; i++) {
                if (!PageCompound(pages[i])) {
                        imu->acct_pages++;
                } else {
                        struct page *hpage;

                        hpage = compound_head(pages[i]);
                        if (hpage == *last_hpage)
                                continue;
                        *last_hpage = hpage;
                        if (headpage_already_acct(ctx, pages, i, hpage))
                                continue;
                        imu->acct_pages += page_size(hpage) >> PAGE_SHIFT;
                }
        }

        if (!imu->acct_pages)
                return 0;

        ret = io_account_mem(ctx, imu->acct_pages, ACCT_PINNED);
        if (ret)
                imu->acct_pages = 0;
        return ret;
}

static int io_sqe_buffer_register(struct io_ring_ctx *ctx, void __user *arg,
                                  unsigned nr_args)
{
        struct vm_area_struct **vmas = NULL;
        struct page **pages = NULL;
        struct page *last_hpage = NULL;
        int i, j, got_pages = 0;
        int ret = -EINVAL;

        if (ctx->user_bufs)
                return -EBUSY;
        if (!nr_args || nr_args > UIO_MAXIOV)
                return -EINVAL;

        ctx->user_bufs = kcalloc(nr_args, sizeof(struct io_mapped_ubuf),
                                        GFP_KERNEL);
        if (!ctx->user_bufs)
                return -ENOMEM;

        for (i = 0; i < nr_args; i++) {
                struct io_mapped_ubuf *imu = &ctx->user_bufs[i];
                unsigned long off, start, end, ubuf;
                int pret, nr_pages;
                struct iovec iov;
                size_t size;

                ret = io_copy_iov(ctx, &iov, arg, i);
                if (ret)
                        goto err;

                /*
                 * Don't impose further limits on the size and buffer
                 * constraints here, we'll -EINVAL later when IO is
                 * submitted if they are wrong.
                 */
                ret = -EFAULT;
                if (!iov.iov_base || !iov.iov_len)
                        goto err;

                /* arbitrary limit, but we need something */
                if (iov.iov_len > SZ_1G)
                        goto err;

                ubuf = (unsigned long) iov.iov_base;
                end = (ubuf + iov.iov_len + PAGE_SIZE - 1) >> PAGE_SHIFT;
                start = ubuf >> PAGE_SHIFT;
                nr_pages = end - start;

                ret = 0;
                if (!pages || nr_pages > got_pages) {
                        kvfree(vmas);
                        kvfree(pages);
                        pages = kvmalloc_array(nr_pages, sizeof(struct page *),
                                                GFP_KERNEL);
                        vmas = kvmalloc_array(nr_pages,
                                        sizeof(struct vm_area_struct *),
                                        GFP_KERNEL);
                        if (!pages || !vmas) {
                                ret = -ENOMEM;
                                goto err;
                        }
                        got_pages = nr_pages;
                }

                imu->bvec = kvmalloc_array(nr_pages, sizeof(struct bio_vec),
                                                GFP_KERNEL);
                ret = -ENOMEM;
                if (!imu->bvec)
                        goto err;

                ret = 0;
                mmap_read_lock(current->mm);
                pret = pin_user_pages(ubuf, nr_pages,
                                      FOLL_WRITE | FOLL_LONGTERM,
                                      pages, vmas);
                if (pret == nr_pages) {
                        /* don't support file backed memory */
                        for (j = 0; j < nr_pages; j++) {
                                struct vm_area_struct *vma = vmas[j];

                                if (vma->vm_file &&
                                    !is_file_hugepages(vma->vm_file)) {
                                        ret = -EOPNOTSUPP;
                                        break;
                                }
                        }
                } else {
                        ret = pret < 0 ? pret : -EFAULT;
                }
                mmap_read_unlock(current->mm);
                if (ret) {
                        /*
                         * if we did partial map, or found file backed vmas,
                         * release any pages we did get
                         */
                        if (pret > 0)
                                unpin_user_pages(pages, pret);
                        kvfree(imu->bvec);
                        goto err;
                }

                ret = io_buffer_account_pin(ctx, pages, pret, imu, &last_hpage);
                if (ret) {
                        unpin_user_pages(pages, pret);
                        kvfree(imu->bvec);
                        goto err;
                }

                off = ubuf & ~PAGE_MASK;
                size = iov.iov_len;
                for (j = 0; j < nr_pages; j++) {
                        size_t vec_len;

                        vec_len = min_t(size_t, size, PAGE_SIZE - off);
                        imu->bvec[j].bv_page = pages[j];
                        imu->bvec[j].bv_len = vec_len;
                        imu->bvec[j].bv_offset = off;
                        off = 0;
                        size -= vec_len;
                }
                /* store original address for later verification */
                imu->ubuf = ubuf;
                imu->len = iov.iov_len;
                imu->nr_bvecs = nr_pages;

                ctx->nr_user_bufs++;
        }
        kvfree(pages);
        kvfree(vmas);
        return 0;
err:
        kvfree(pages);
        kvfree(vmas);
        io_sqe_buffer_unregister(ctx);
        return ret;
}

static int io_eventfd_register(struct io_ring_ctx *ctx, void __user *arg)
{
        __s32 __user *fds = arg;
        int fd;

        if (ctx->cq_ev_fd)
                return -EBUSY;

        if (copy_from_user(&fd, fds, sizeof(*fds)))
                return -EFAULT;

        ctx->cq_ev_fd = eventfd_ctx_fdget(fd);
        if (IS_ERR(ctx->cq_ev_fd)) {
                int ret = PTR_ERR(ctx->cq_ev_fd);
                ctx->cq_ev_fd = NULL;
                return ret;
        }

        return 0;
}

static int io_eventfd_unregister(struct io_ring_ctx *ctx)
{
        if (ctx->cq_ev_fd) {
                eventfd_ctx_put(ctx->cq_ev_fd);
                ctx->cq_ev_fd = NULL;
                return 0;
        }

        return -ENXIO;
}

static int __io_destroy_buffers(int id, void *p, void *data)
{
        struct io_ring_ctx *ctx = data;
        struct io_buffer *buf = p;

        __io_remove_buffers(ctx, buf, id, -1U);
        return 0;
}

static void io_destroy_buffers(struct io_ring_ctx *ctx)
{
        idr_for_each(&ctx->io_buffer_idr, __io_destroy_buffers, ctx);
        idr_destroy(&ctx->io_buffer_idr);
}

static void io_ring_ctx_free(struct io_ring_ctx *ctx)
{
        io_finish_async(ctx);
        io_sqe_buffer_unregister(ctx);

        if (ctx->sqo_task) {
                put_task_struct(ctx->sqo_task);
                ctx->sqo_task = NULL;
                mmdrop(ctx->mm_account);
                ctx->mm_account = NULL;
        }

#ifdef CONFIG_BLK_CGROUP
        if (ctx->sqo_blkcg_css)
                css_put(ctx->sqo_blkcg_css);
#endif

        io_sqe_files_unregister(ctx);
        io_eventfd_unregister(ctx);
        io_destroy_buffers(ctx);
        idr_destroy(&ctx->personality_idr);

#if defined(CONFIG_UNIX)
        if (ctx->ring_sock) {
                ctx->ring_sock->file = NULL; /* so that iput() is called */
                sock_release(ctx->ring_sock);
        }
#endif

        io_mem_free(ctx->rings);
        io_mem_free(ctx->sq_sqes);

        percpu_ref_exit(&ctx->refs);
        free_uid(ctx->user);
        put_cred(ctx->creds);
        kfree(ctx->cancel_hash);
        kmem_cache_free(req_cachep, ctx->fallback_req);
        kfree(ctx);
}

static __poll_t io_uring_poll(struct file *file, poll_table *wait)
{
        struct io_ring_ctx *ctx = file->private_data;
        __poll_t mask = 0;

        poll_wait(file, &ctx->cq_wait, wait);
        /*
         * synchronizes with barrier from wq_has_sleeper call in
         * io_commit_cqring
         */
        smp_rmb();
        if (!io_sqring_full(ctx))
                mask |= EPOLLOUT | EPOLLWRNORM;
        io_cqring_overflow_flush(ctx, false, NULL, NULL);
        if (io_cqring_events(ctx))
                mask |= EPOLLIN | EPOLLRDNORM;

        return mask;
}

static int io_uring_fasync(int fd, struct file *file, int on)
{
        struct io_ring_ctx *ctx = file->private_data;

        return fasync_helper(fd, file, on, &ctx->cq_fasync);
}

static int io_remove_personalities(int id, void *p, void *data)
{
        struct io_ring_ctx *ctx = data;
        struct io_identity *iod;

        iod = idr_remove(&ctx->personality_idr, id);
        if (iod) {
                put_cred(iod->creds);
                if (refcount_dec_and_test(&iod->count))
                        kfree(iod);
        }
        return 0;
}

static void io_ring_exit_work(struct work_struct *work)
{
        struct io_ring_ctx *ctx = container_of(work, struct io_ring_ctx,
                                               exit_work);

        /*
         * If we're doing polled IO and end up having requests being
         * submitted async (out-of-line), then completions can come in while
         * we're waiting for refs to drop. We need to reap these manually,
         * as nobody else will be looking for them.
         */
        do {
                __io_uring_cancel_task_requests(ctx, NULL);
        } while (!wait_for_completion_timeout(&ctx->ref_comp, HZ/20));
        io_ring_ctx_free(ctx);
}

static bool io_cancel_ctx_cb(struct io_wq_work *work, void *data)
{
        struct io_kiocb *req = container_of(work, struct io_kiocb, work);

        return req->ctx == data;
}

static void io_ring_ctx_wait_and_kill(struct io_ring_ctx *ctx)
{
        mutex_lock(&ctx->uring_lock);
        percpu_ref_kill(&ctx->refs);
        /* if force is set, the ring is going away. always drop after that */
        ctx->cq_overflow_flushed = 1;
        if (ctx->rings)
                __io_cqring_overflow_flush(ctx, true, NULL, NULL);
        mutex_unlock(&ctx->uring_lock);

        io_kill_timeouts(ctx, NULL, NULL);
        io_poll_remove_all(ctx, NULL, NULL);

        if (ctx->io_wq)
                io_wq_cancel_cb(ctx->io_wq, io_cancel_ctx_cb, ctx, true);

        /* if we failed setting up the ctx, we might not have any rings */
        io_iopoll_try_reap_events(ctx);
        idr_for_each(&ctx->personality_idr, io_remove_personalities, ctx);

        /*
         * Do this upfront, so we won't have a grace period where the ring
         * is closed but resources aren't reaped yet. This can cause
         * spurious failure in setting up a new ring.
         */
        io_unaccount_mem(ctx, ring_pages(ctx->sq_entries, ctx->cq_entries),
                         ACCT_LOCKED);

        INIT_WORK(&ctx->exit_work, io_ring_exit_work);
        /*
         * Use system_unbound_wq to avoid spawning tons of event kworkers
         * if we're exiting a ton of rings at the same time. It just adds
         * noise and overhead, there's no discernable change in runtime
         * over using system_wq.
         */
        queue_work(system_unbound_wq, &ctx->exit_work);
}

static int io_uring_release(struct inode *inode, struct file *file)
{
        struct io_ring_ctx *ctx = file->private_data;

        file->private_data = NULL;
        io_ring_ctx_wait_and_kill(ctx);
        return 0;
}

struct io_task_cancel {
        struct task_struct *task;
        struct files_struct *files;
};

static bool io_cancel_task_cb(struct io_wq_work *work, void *data)
{
        struct io_kiocb *req = container_of(work, struct io_kiocb, work);
        struct io_task_cancel *cancel = data;
        bool ret;

        if (cancel->files && (req->flags & REQ_F_LINK_TIMEOUT)) {
                unsigned long flags;
                struct io_ring_ctx *ctx = req->ctx;

                /* protect against races with linked timeouts */
                spin_lock_irqsave(&ctx->completion_lock, flags);
                ret = io_match_task(req, cancel->task, cancel->files);
                spin_unlock_irqrestore(&ctx->completion_lock, flags);
        } else {
                ret = io_match_task(req, cancel->task, cancel->files);
        }
        return ret;
}

static void io_cancel_defer_files(struct io_ring_ctx *ctx,
                                  struct task_struct *task,
                                  struct files_struct *files)
{
        struct io_defer_entry *de = NULL;
        LIST_HEAD(list);

        spin_lock_irq(&ctx->completion_lock);
        list_for_each_entry_reverse(de, &ctx->defer_list, list) {
                if (io_match_task(de->req, task, files)) {
                        list_cut_position(&list, &ctx->defer_list, &de->list);
                        break;
                }
        }
        spin_unlock_irq(&ctx->completion_lock);

        while (!list_empty(&list)) {
                de = list_first_entry(&list, struct io_defer_entry, list);
                list_del_init(&de->list);
                req_set_fail_links(de->req);
                io_put_req(de->req);
                io_req_complete(de->req, -ECANCELED);
                kfree(de);
        }
}

static void io_uring_cancel_files(struct io_ring_ctx *ctx,
                                  struct task_struct *task,
                                  struct files_struct *files)
{
        while (!list_empty_careful(&ctx->inflight_list)) {
                struct io_task_cancel cancel = { .task = task, .files = files };
                struct io_kiocb *req;
                DEFINE_WAIT(wait);
                bool found = false;

                spin_lock_irq(&ctx->inflight_lock);
                list_for_each_entry(req, &ctx->inflight_list, inflight_entry) {
                        if (req->task != task ||
                            req->work.identity->files != files)
                                continue;
                        found = true;
                        break;
                }
                if (found)
                        prepare_to_wait(&task->io_uring->wait, &wait,
                                        TASK_UNINTERRUPTIBLE);
                spin_unlock_irq(&ctx->inflight_lock);

                /* We need to keep going until we don't find a matching req */
                if (!found)
                        break;

                io_wq_cancel_cb(ctx->io_wq, io_cancel_task_cb, &cancel, true);
                io_poll_remove_all(ctx, task, files);
                io_kill_timeouts(ctx, task, files);
                /* cancellations _may_ trigger task work */
                io_run_task_work();
                schedule();
                finish_wait(&task->io_uring->wait, &wait);
        }
}

static void __io_uring_cancel_task_requests(struct io_ring_ctx *ctx,
                                            struct task_struct *task)
{
        while (1) {
                struct io_task_cancel cancel = { .task = task, .files = NULL, };
                enum io_wq_cancel cret;
                bool ret = false;

                if (ctx->io_wq) {
                        cret = io_wq_cancel_cb(ctx->io_wq, io_cancel_task_cb,
                                               &cancel, true);
                        ret |= (cret != IO_WQ_CANCEL_NOTFOUND);
                }

                /* SQPOLL thread does its own polling */
                if (!(ctx->flags & IORING_SETUP_SQPOLL)) {
                        while (!list_empty_careful(&ctx->iopoll_list)) {
                                io_iopoll_try_reap_events(ctx);
                                ret = true;
                        }
                }

                ret |= io_poll_remove_all(ctx, task, NULL);
                ret |= io_kill_timeouts(ctx, task, NULL);
                ret |= io_run_task_work();
                if (!ret)
                        break;
                cond_resched();
        }
}

/*
 * We need to iteratively cancel requests, in case a request has dependent
 * hard links. These persist even for failure of cancelations, hence keep
 * looping until none are found.
 */
static void io_uring_cancel_task_requests(struct io_ring_ctx *ctx,
                                          struct files_struct *files)
{
        struct task_struct *task = current;

        if ((ctx->flags & IORING_SETUP_SQPOLL) && ctx->sq_data) {
                task = ctx->sq_data->thread;
                atomic_inc(&task->io_uring->in_idle);
                io_sq_thread_park(ctx->sq_data);
        }

        io_cancel_defer_files(ctx, task, files);
        io_cqring_overflow_flush(ctx, true, task, files);

        if (!files)
                __io_uring_cancel_task_requests(ctx, task);
        else
                io_uring_cancel_files(ctx, task, files);

        if ((ctx->flags & IORING_SETUP_SQPOLL) && ctx->sq_data) {
                atomic_dec(&task->io_uring->in_idle);
                /*
                 * If the files that are going away are the ones in the thread
                 * identity, clear them out.
                 */
                if (task->io_uring->identity->files == files)
                        task->io_uring->identity->files = NULL;
                io_sq_thread_unpark(ctx->sq_data);
        }
}

/*
 * Note that this task has used io_uring. We use it for cancelation purposes.
 */
static int io_uring_add_task_file(struct io_ring_ctx *ctx, struct file *file)
{
        struct io_uring_task *tctx = current->io_uring;
        int ret;

        if (unlikely(!tctx)) {
                ret = io_uring_alloc_task_context(current);
                if (unlikely(ret))
                        return ret;
                tctx = current->io_uring;
        }
        if (tctx->last != file) {
                void *old = xa_load(&tctx->xa, (unsigned long)file);

                if (!old) {
                        get_file(file);
                        ret = xa_err(xa_store(&tctx->xa, (unsigned long)file,
                                                file, GFP_KERNEL));
                        if (ret) {
                                fput(file);
                                return ret;
                        }
                }
                tctx->last = file;
        }

        /*
         * This is race safe in that the task itself is doing this, hence it
         * cannot be going through the exit/cancel paths at the same time.
         * This cannot be modified while exit/cancel is running.
         */
        if (!tctx->sqpoll && (ctx->flags & IORING_SETUP_SQPOLL))
                tctx->sqpoll = true;

        return 0;
}

/*
 * Remove this io_uring_file -> task mapping.
 */
static void io_uring_del_task_file(struct file *file)
{
        struct io_uring_task *tctx = current->io_uring;

        if (tctx->last == file)
                tctx->last = NULL;
        file = xa_erase(&tctx->xa, (unsigned long)file);
        if (file)
                fput(file);
}

/*
 * Drop task note for this file if we're the only ones that hold it after
 * pending fput()
 */
static void io_uring_attempt_task_drop(struct file *file)
{
        if (!current->io_uring)
                return;
        /*
         * fput() is pending, will be 2 if the only other ref is our potential
         * task file note. If the task is exiting, drop regardless of count.
         */
        if (fatal_signal_pending(current) || (current->flags & PF_EXITING) ||
            atomic_long_read(&file->f_count) == 2)
                io_uring_del_task_file(file);
}

static void io_uring_remove_task_files(struct io_uring_task *tctx)
{
        struct file *file;
        unsigned long index;

        xa_for_each(&tctx->xa, index, file)
                io_uring_del_task_file(file);
}

void __io_uring_files_cancel(struct files_struct *files)
{
        struct io_uring_task *tctx = current->io_uring;
        struct file *file;
        unsigned long index;

        /* make sure overflow events are dropped */
        atomic_inc(&tctx->in_idle);
        xa_for_each(&tctx->xa, index, file)
                io_uring_cancel_task_requests(file->private_data, files);
        atomic_dec(&tctx->in_idle);

        if (files)
                io_uring_remove_task_files(tctx);
}

static s64 tctx_inflight(struct io_uring_task *tctx)
{
        unsigned long index;
        struct file *file;
        s64 inflight;

        inflight = percpu_counter_sum(&tctx->inflight);
        if (!tctx->sqpoll)
                return inflight;

        /*
         * If we have SQPOLL rings, then we need to iterate and find them, and
         * add the pending count for those.
         */
        xa_for_each(&tctx->xa, index, file) {
                struct io_ring_ctx *ctx = file->private_data;

                if (ctx->flags & IORING_SETUP_SQPOLL) {
                        struct io_uring_task *__tctx = ctx->sqo_task->io_uring;

                        inflight += percpu_counter_sum(&__tctx->inflight);
                }
        }

        return inflight;
}

/*
 * Find any io_uring fd that this task has registered or done IO on, and cancel
 * requests.
 */
void __io_uring_task_cancel(void)
{
        struct io_uring_task *tctx = current->io_uring;
        DEFINE_WAIT(wait);
        s64 inflight;

        /* make sure overflow events are dropped */
        atomic_inc(&tctx->in_idle);

        do {
                /* read completions before cancelations */
                inflight = tctx_inflight(tctx);
                if (!inflight)
                        break;
                __io_uring_files_cancel(NULL);

                prepare_to_wait(&tctx->wait, &wait, TASK_UNINTERRUPTIBLE);

                /*
                 * If we've seen completions, retry. This avoids a race where
                 * a completion comes in before we did prepare_to_wait().
                 */
                if (inflight != tctx_inflight(tctx))
                        continue;
                schedule();
                finish_wait(&tctx->wait, &wait);
        } while (1);

        atomic_dec(&tctx->in_idle);

        io_uring_remove_task_files(tctx);
}

static int io_uring_flush(struct file *file, void *data)
{
        io_uring_attempt_task_drop(file);
        return 0;
}

static void *io_uring_validate_mmap_request(struct file *file,
                                            loff_t pgoff, size_t sz)
{
        struct io_ring_ctx *ctx = file->private_data;
        loff_t offset = pgoff << PAGE_SHIFT;
        struct page *page;
        void *ptr;

        switch (offset) {
        case IORING_OFF_SQ_RING:
        case IORING_OFF_CQ_RING:
                ptr = ctx->rings;
                break;
        case IORING_OFF_SQES:
                ptr = ctx->sq_sqes;
                break;
        default:
                return ERR_PTR(-EINVAL);
        }

        page = virt_to_head_page(ptr);
        if (sz > page_size(page))
                return ERR_PTR(-EINVAL);

        return ptr;
}

#ifdef CONFIG_MMU

static int io_uring_mmap(struct file *file, struct vm_area_struct *vma)
{
        size_t sz = vma->vm_end - vma->vm_start;
        unsigned long pfn;
        void *ptr;

        ptr = io_uring_validate_mmap_request(file, vma->vm_pgoff, sz);
        if (IS_ERR(ptr))
                return PTR_ERR(ptr);

        pfn = virt_to_phys(ptr) >> PAGE_SHIFT;
        return remap_pfn_range(vma, vma->vm_start, pfn, sz, vma->vm_page_prot);
}

#else /* !CONFIG_MMU */

static int io_uring_mmap(struct file *file, struct vm_area_struct *vma)
{
        return vma->vm_flags & (VM_SHARED | VM_MAYSHARE) ? 0 : -EINVAL;
}

static unsigned int io_uring_nommu_mmap_capabilities(struct file *file)
{
        return NOMMU_MAP_DIRECT | NOMMU_MAP_READ | NOMMU_MAP_WRITE;
}

static unsigned long io_uring_nommu_get_unmapped_area(struct file *file,
        unsigned long addr, unsigned long len,
        unsigned long pgoff, unsigned long flags)
{
        void *ptr;

        ptr = io_uring_validate_mmap_request(file, pgoff, len);
        if (IS_ERR(ptr))
                return PTR_ERR(ptr);

        return (unsigned long) ptr;
}

#endif /* !CONFIG_MMU */

static void io_sqpoll_wait_sq(struct io_ring_ctx *ctx)
{
        DEFINE_WAIT(wait);

        do {
                if (!io_sqring_full(ctx))
                        break;

                prepare_to_wait(&ctx->sqo_sq_wait, &wait, TASK_INTERRUPTIBLE);

                if (!io_sqring_full(ctx))
                        break;

                schedule();
        } while (!signal_pending(current));

        finish_wait(&ctx->sqo_sq_wait, &wait);
}

static int io_get_ext_arg(unsigned flags, const void __user *argp, size_t *argsz,
                          struct __kernel_timespec __user **ts,
                          const sigset_t __user **sig)
{
        struct io_uring_getevents_arg arg;

        /*
         * If EXT_ARG isn't set, then we have no timespec and the argp pointer
         * is just a pointer to the sigset_t.
         */
        if (!(flags & IORING_ENTER_EXT_ARG)) {
                *sig = (const sigset_t __user *) argp;
                *ts = NULL;
                return 0;
        }

        /*
         * EXT_ARG is set - ensure we agree on the size of it and copy in our
         * timespec and sigset_t pointers if good.
         */
        if (*argsz != sizeof(arg))
                return -EINVAL;
        if (copy_from_user(&arg, argp, sizeof(arg)))
                return -EFAULT;
        *sig = u64_to_user_ptr(arg.sigmask);
        *argsz = arg.sigmask_sz;
        *ts = u64_to_user_ptr(arg.ts);
        return 0;
}

SYSCALL_DEFINE6(io_uring_enter, unsigned int, fd, u32, to_submit,
                u32, min_complete, u32, flags, const void __user *, argp,
                size_t, argsz)
{
        struct io_ring_ctx *ctx;
        long ret = -EBADF;
        int submitted = 0;
        struct fd f;

        io_run_task_work();

        if (flags & ~(IORING_ENTER_GETEVENTS | IORING_ENTER_SQ_WAKEUP |
                        IORING_ENTER_SQ_WAIT | IORING_ENTER_EXT_ARG))
                return -EINVAL;

        f = fdget(fd);
        if (!f.file)
                return -EBADF;

        ret = -EOPNOTSUPP;
        if (f.file->f_op != &io_uring_fops)
                goto out_fput;

        ret = -ENXIO;
        ctx = f.file->private_data;
        if (!percpu_ref_tryget(&ctx->refs))
                goto out_fput;

        ret = -EBADFD;
        if (ctx->flags & IORING_SETUP_R_DISABLED)
                goto out;

        /*
         * For SQ polling, the thread will do all submissions and completions.
         * Just return the requested submit count, and wake the thread if
         * we were asked to.
         */
        ret = 0;
        if (ctx->flags & IORING_SETUP_SQPOLL) {
                io_cqring_overflow_flush(ctx, false, NULL, NULL);

                if (flags & IORING_ENTER_SQ_WAKEUP)
                        wake_up(&ctx->sq_data->wait);
                if (flags & IORING_ENTER_SQ_WAIT)
                        io_sqpoll_wait_sq(ctx);
                submitted = to_submit;
        } else if (to_submit) {
                ret = io_uring_add_task_file(ctx, f.file);
                if (unlikely(ret))
                        goto out;
                mutex_lock(&ctx->uring_lock);
                submitted = io_submit_sqes(ctx, to_submit);
                mutex_unlock(&ctx->uring_lock);

                if (submitted != to_submit)
                        goto out;
        }
        if (flags & IORING_ENTER_GETEVENTS) {
                const sigset_t __user *sig;
                struct __kernel_timespec __user *ts;

                ret = io_get_ext_arg(flags, argp, &argsz, &ts, &sig);
                if (unlikely(ret))
                        goto out;

                min_complete = min(min_complete, ctx->cq_entries);

                /*
                 * When SETUP_IOPOLL and SETUP_SQPOLL are both enabled, user
                 * space applications don't need to do io completion events
                 * polling again, they can rely on io_sq_thread to do polling
                 * work, which can reduce cpu usage and uring_lock contention.
                 */
                if (ctx->flags & IORING_SETUP_IOPOLL &&
                    !(ctx->flags & IORING_SETUP_SQPOLL)) {
                        ret = io_iopoll_check(ctx, min_complete);
                } else {
                        ret = io_cqring_wait(ctx, min_complete, sig, argsz, ts);
                }
        }

out:
        percpu_ref_put(&ctx->refs);
out_fput:
        fdput(f);
        return submitted ? submitted : ret;
}

#ifdef CONFIG_PROC_FS
static int io_uring_show_cred(int id, void *p, void *data)
{
        struct io_identity *iod = p;
        const struct cred *cred = iod->creds;
        struct seq_file *m = data;
        struct user_namespace *uns = seq_user_ns(m);
        struct group_info *gi;
        kernel_cap_t cap;
        unsigned __capi;
        int g;

        seq_printf(m, "%5d\n", id);
        seq_put_decimal_ull(m, "\tUid:\t", from_kuid_munged(uns, cred->uid));
        seq_put_decimal_ull(m, "\t\t", from_kuid_munged(uns, cred->euid));
        seq_put_decimal_ull(m, "\t\t", from_kuid_munged(uns, cred->suid));
        seq_put_decimal_ull(m, "\t\t", from_kuid_munged(uns, cred->fsuid));
        seq_put_decimal_ull(m, "\n\tGid:\t", from_kgid_munged(uns, cred->gid));
        seq_put_decimal_ull(m, "\t\t", from_kgid_munged(uns, cred->egid));
        seq_put_decimal_ull(m, "\t\t", from_kgid_munged(uns, cred->sgid));
        seq_put_decimal_ull(m, "\t\t", from_kgid_munged(uns, cred->fsgid));
        seq_puts(m, "\n\tGroups:\t");
        gi = cred->group_info;
        for (g = 0; g < gi->ngroups; g++) {
                seq_put_decimal_ull(m, g ? " " : "",
                                        from_kgid_munged(uns, gi->gid[g]));
        }
        seq_puts(m, "\n\tCapEff:\t");
        cap = cred->cap_effective;
        CAP_FOR_EACH_U32(__capi)
                seq_put_hex_ll(m, NULL, cap.cap[CAP_LAST_U32 - __capi], 8);
        seq_putc(m, '\n');
        return 0;
}

static void __io_uring_show_fdinfo(struct io_ring_ctx *ctx, struct seq_file *m)
{
        struct io_sq_data *sq = NULL;
        bool has_lock;
        int i;

        /*
         * Avoid ABBA deadlock between the seq lock and the io_uring mutex,
         * since fdinfo case grabs it in the opposite direction of normal use
         * cases. If we fail to get the lock, we just don't iterate any
         * structures that could be going away outside the io_uring mutex.
         */
        has_lock = mutex_trylock(&ctx->uring_lock);

        if (has_lock && (ctx->flags & IORING_SETUP_SQPOLL))
                sq = ctx->sq_data;

        seq_printf(m, "SqThread:\t%d\n", sq ? task_pid_nr(sq->thread) : -1);
        seq_printf(m, "SqThreadCpu:\t%d\n", sq ? task_cpu(sq->thread) : -1);
        seq_printf(m, "UserFiles:\t%u\n", ctx->nr_user_files);
        for (i = 0; has_lock && i < ctx->nr_user_files; i++) {
                struct fixed_file_table *table;
                struct file *f;

                table = &ctx->file_data->table[i >> IORING_FILE_TABLE_SHIFT];
                f = table->files[i & IORING_FILE_TABLE_MASK];
                if (f)
                        seq_printf(m, "%5u: %s\n", i, file_dentry(f)->d_iname);
                else
                        seq_printf(m, "%5u: <none>\n", i);
        }
        seq_printf(m, "UserBufs:\t%u\n", ctx->nr_user_bufs);
        for (i = 0; has_lock && i < ctx->nr_user_bufs; i++) {
                struct io_mapped_ubuf *buf = &ctx->user_bufs[i];

                seq_printf(m, "%5u: 0x%llx/%u\n", i, buf->ubuf,
                                                (unsigned int) buf->len);
        }
        if (has_lock && !idr_is_empty(&ctx->personality_idr)) {
                seq_printf(m, "Personalities:\n");
                idr_for_each(&ctx->personality_idr, io_uring_show_cred, m);
        }
        seq_printf(m, "PollList:\n");
        spin_lock_irq(&ctx->completion_lock);
        for (i = 0; i < (1U << ctx->cancel_hash_bits); i++) {
                struct hlist_head *list = &ctx->cancel_hash[i];
                struct io_kiocb *req;

                hlist_for_each_entry(req, list, hash_node)
                        seq_printf(m, "  op=%d, task_works=%d\n", req->opcode,
                                        req->task->task_works != NULL);
        }
        spin_unlock_irq(&ctx->completion_lock);
        if (has_lock)
                mutex_unlock(&ctx->uring_lock);
}

static void io_uring_show_fdinfo(struct seq_file *m, struct file *f)
{
        struct io_ring_ctx *ctx = f->private_data;

        if (percpu_ref_tryget(&ctx->refs)) {
                __io_uring_show_fdinfo(ctx, m);
                percpu_ref_put(&ctx->refs);
        }
}
#endif

static const struct file_operations io_uring_fops = {
        .release        = io_uring_release,
        .flush          = io_uring_flush,
        .mmap           = io_uring_mmap,
#ifndef CONFIG_MMU
        .get_unmapped_area = io_uring_nommu_get_unmapped_area,
        .mmap_capabilities = io_uring_nommu_mmap_capabilities,
#endif
        .poll           = io_uring_poll,
        .fasync         = io_uring_fasync,
#ifdef CONFIG_PROC_FS
        .show_fdinfo    = io_uring_show_fdinfo,
#endif
};

static int io_allocate_scq_urings(struct io_ring_ctx *ctx,
                                  struct io_uring_params *p)
{
        struct io_rings *rings;
        size_t size, sq_array_offset;

        /* make sure these are sane, as we already accounted them */
        ctx->sq_entries = p->sq_entries;
        ctx->cq_entries = p->cq_entries;

        size = rings_size(p->sq_entries, p->cq_entries, &sq_array_offset);
        if (size == SIZE_MAX)
                return -EOVERFLOW;

        rings = io_mem_alloc(size);
        if (!rings)
                return -ENOMEM;

        ctx->rings = rings;
        ctx->sq_array = (u32 *)((char *)rings + sq_array_offset);
        rings->sq_ring_mask = p->sq_entries - 1;
        rings->cq_ring_mask = p->cq_entries - 1;
        rings->sq_ring_entries = p->sq_entries;
        rings->cq_ring_entries = p->cq_entries;
        ctx->sq_mask = rings->sq_ring_mask;
        ctx->cq_mask = rings->cq_ring_mask;

        size = array_size(sizeof(struct io_uring_sqe), p->sq_entries);
        if (size == SIZE_MAX) {
                io_mem_free(ctx->rings);
                ctx->rings = NULL;
                return -EOVERFLOW;
        }

        ctx->sq_sqes = io_mem_alloc(size);
        if (!ctx->sq_sqes) {
                io_mem_free(ctx->rings);
                ctx->rings = NULL;
                return -ENOMEM;
        }

        return 0;
}

static int io_uring_install_fd(struct io_ring_ctx *ctx, struct file *file)
{
        int ret, fd;

        fd = get_unused_fd_flags(O_RDWR | O_CLOEXEC);
        if (fd < 0)
                return fd;

        ret = io_uring_add_task_file(ctx, file);
        if (ret) {
                put_unused_fd(fd);
                return ret;
        }
        fd_install(fd, file);
        return fd;
}

/*
 * Allocate an anonymous fd, this is what constitutes the application
 * visible backing of an io_uring instance. The application mmaps this
 * fd to gain access to the SQ/CQ ring details. If UNIX sockets are enabled,
 * we have to tie this fd to a socket for file garbage collection purposes.
 */
static struct file *io_uring_get_file(struct io_ring_ctx *ctx)
{
        struct file *file;
#if defined(CONFIG_UNIX)
        int ret;

        ret = sock_create_kern(&init_net, PF_UNIX, SOCK_RAW, IPPROTO_IP,
                                &ctx->ring_sock);
        if (ret)
                return ERR_PTR(ret);
#endif

        file = anon_inode_getfile("[io_uring]", &io_uring_fops, ctx,
                                        O_RDWR | O_CLOEXEC);
#if defined(CONFIG_UNIX)
        if (IS_ERR(file)) {
                sock_release(ctx->ring_sock);
                ctx->ring_sock = NULL;
        } else {
                ctx->ring_sock->file = file;
        }
#endif
        return file;
}

static int io_uring_create(unsigned entries, struct io_uring_params *p,
                           struct io_uring_params __user *params)
{
        struct user_struct *user = NULL;
        struct io_ring_ctx *ctx;
        struct file *file;
        bool limit_mem;
        int ret;

        if (!entries)
                return -EINVAL;
        if (entries > IORING_MAX_ENTRIES) {
                if (!(p->flags & IORING_SETUP_CLAMP))
                        return -EINVAL;
                entries = IORING_MAX_ENTRIES;
        }

        /*
         * Use twice as many entries for the CQ ring. It's possible for the
         * application to drive a higher depth than the size of the SQ ring,
         * since the sqes are only used at submission time. This allows for
         * some flexibility in overcommitting a bit. If the application has
         * set IORING_SETUP_CQSIZE, it will have passed in the desired number
         * of CQ ring entries manually.
         */
        p->sq_entries = roundup_pow_of_two(entries);
        if (p->flags & IORING_SETUP_CQSIZE) {
                /*
                 * If IORING_SETUP_CQSIZE is set, we do the same roundup
                 * to a power-of-two, if it isn't already. We do NOT impose
                 * any cq vs sq ring sizing.
                 */
                if (!p->cq_entries)
                        return -EINVAL;
                if (p->cq_entries > IORING_MAX_CQ_ENTRIES) {
                        if (!(p->flags & IORING_SETUP_CLAMP))
                                return -EINVAL;
                        p->cq_entries = IORING_MAX_CQ_ENTRIES;
                }
                p->cq_entries = roundup_pow_of_two(p->cq_entries);
                if (p->cq_entries < p->sq_entries)
                        return -EINVAL;
        } else {
                p->cq_entries = 2 * p->sq_entries;
        }

        user = get_uid(current_user());
        limit_mem = !capable(CAP_IPC_LOCK);

        if (limit_mem) {
                ret = __io_account_mem(user,
                                ring_pages(p->sq_entries, p->cq_entries));
                if (ret) {
                        free_uid(user);
                        return ret;
                }
        }

        ctx = io_ring_ctx_alloc(p);
        if (!ctx) {
                if (limit_mem)
                        __io_unaccount_mem(user, ring_pages(p->sq_entries,
                                                                p->cq_entries));
                free_uid(user);
                return -ENOMEM;
        }
        ctx->compat = in_compat_syscall();
        ctx->user = user;
        ctx->creds = get_current_cred();
#ifdef CONFIG_AUDIT
        ctx->loginuid = current->loginuid;
        ctx->sessionid = current->sessionid;
#endif
        ctx->sqo_task = get_task_struct(current);

        /*
         * This is just grabbed for accounting purposes. When a process exits,
         * the mm is exited and dropped before the files, hence we need to hang
         * on to this mm purely for the purposes of being able to unaccount
         * memory (locked/pinned vm). It's not used for anything else.
         */
        mmgrab(current->mm);
        ctx->mm_account = current->mm;

#ifdef CONFIG_BLK_CGROUP
        /*
         * The sq thread will belong to the original cgroup it was inited in.
         * If the cgroup goes offline (e.g. disabling the io controller), then
         * issued bios will be associated with the closest cgroup later in the
         * block layer.
         */
        rcu_read_lock();
        ctx->sqo_blkcg_css = blkcg_css();
        ret = css_tryget_online(ctx->sqo_blkcg_css);
        rcu_read_unlock();
        if (!ret) {
                /* don't init against a dying cgroup, have the user try again */
                ctx->sqo_blkcg_css = NULL;
                ret = -ENODEV;
                goto err;
        }
#endif

        /*
         * Account memory _before_ installing the file descriptor. Once
         * the descriptor is installed, it can get closed at any time. Also
         * do this before hitting the general error path, as ring freeing
         * will un-account as well.
         */
        io_account_mem(ctx, ring_pages(p->sq_entries, p->cq_entries),
                       ACCT_LOCKED);
        ctx->limit_mem = limit_mem;

        ret = io_allocate_scq_urings(ctx, p);
        if (ret)
                goto err;

        ret = io_sq_offload_create(ctx, p);
        if (ret)
                goto err;

        if (!(p->flags & IORING_SETUP_R_DISABLED))
                io_sq_offload_start(ctx);

        memset(&p->sq_off, 0, sizeof(p->sq_off));
        p->sq_off.head = offsetof(struct io_rings, sq.head);
        p->sq_off.tail = offsetof(struct io_rings, sq.tail);
        p->sq_off.ring_mask = offsetof(struct io_rings, sq_ring_mask);
        p->sq_off.ring_entries = offsetof(struct io_rings, sq_ring_entries);
        p->sq_off.flags = offsetof(struct io_rings, sq_flags);
        p->sq_off.dropped = offsetof(struct io_rings, sq_dropped);
        p->sq_off.array = (char *)ctx->sq_array - (char *)ctx->rings;

        memset(&p->cq_off, 0, sizeof(p->cq_off));
        p->cq_off.head = offsetof(struct io_rings, cq.head);
        p->cq_off.tail = offsetof(struct io_rings, cq.tail);
        p->cq_off.ring_mask = offsetof(struct io_rings, cq_ring_mask);
        p->cq_off.ring_entries = offsetof(struct io_rings, cq_ring_entries);
        p->cq_off.overflow = offsetof(struct io_rings, cq_overflow);
        p->cq_off.cqes = offsetof(struct io_rings, cqes);
        p->cq_off.flags = offsetof(struct io_rings, cq_flags);

        p->features = IORING_FEAT_SINGLE_MMAP | IORING_FEAT_NODROP |
                        IORING_FEAT_SUBMIT_STABLE | IORING_FEAT_RW_CUR_POS |
                        IORING_FEAT_CUR_PERSONALITY | IORING_FEAT_FAST_POLL |
                        IORING_FEAT_POLL_32BITS | IORING_FEAT_SQPOLL_NONFIXED |
                        IORING_FEAT_EXT_ARG;

        if (copy_to_user(params, p, sizeof(*p))) {
                ret = -EFAULT;
                goto err;
        }

        file = io_uring_get_file(ctx);
        if (IS_ERR(file)) {
                ret = PTR_ERR(file);
                goto err;
        }

        /*
         * Install ring fd as the very last thing, so we don't risk someone
         * having closed it before we finish setup
         */
        ret = io_uring_install_fd(ctx, file);
        if (ret < 0) {
                /* fput will clean it up */
                fput(file);
                return ret;
        }

        trace_io_uring_create(ret, ctx, p->sq_entries, p->cq_entries, p->flags);
        return ret;
err:
        io_ring_ctx_wait_and_kill(ctx);
        return ret;
}

/*
 * Sets up an aio uring context, and returns the fd. Applications asks for a
 * ring size, we return the actual sq/cq ring sizes (among other things) in the
 * params structure passed in.
 */
static long io_uring_setup(u32 entries, struct io_uring_params __user *params)
{
        struct io_uring_params p;
        int i;

        if (copy_from_user(&p, params, sizeof(p)))
                return -EFAULT;
        for (i = 0; i < ARRAY_SIZE(p.resv); i++) {
                if (p.resv[i])
                        return -EINVAL;
        }

        if (p.flags & ~(IORING_SETUP_IOPOLL | IORING_SETUP_SQPOLL |
                        IORING_SETUP_SQ_AFF | IORING_SETUP_CQSIZE |
                        IORING_SETUP_CLAMP | IORING_SETUP_ATTACH_WQ |
                        IORING_SETUP_R_DISABLED))
                return -EINVAL;

        return  io_uring_create(entries, &p, params);
}

SYSCALL_DEFINE2(io_uring_setup, u32, entries,
                struct io_uring_params __user *, params)
{
        return io_uring_setup(entries, params);
}

static int io_probe(struct io_ring_ctx *ctx, void __user *arg, unsigned nr_args)
{
        struct io_uring_probe *p;
        size_t size;
        int i, ret;

        size = struct_size(p, ops, nr_args);
        if (size == SIZE_MAX)
                return -EOVERFLOW;
        p = kzalloc(size, GFP_KERNEL);
        if (!p)
                return -ENOMEM;

        ret = -EFAULT;
        if (copy_from_user(p, arg, size))
                goto out;
        ret = -EINVAL;
        if (memchr_inv(p, 0, size))
                goto out;

        p->last_op = IORING_OP_LAST - 1;
        if (nr_args > IORING_OP_LAST)
                nr_args = IORING_OP_LAST;

        for (i = 0; i < nr_args; i++) {
                p->ops[i].op = i;
                if (!io_op_defs[i].not_supported)
                        p->ops[i].flags = IO_URING_OP_SUPPORTED;
        }
        p->ops_len = i;

        ret = 0;
        if (copy_to_user(arg, p, size))
                ret = -EFAULT;
out:
        kfree(p);
        return ret;
}

static int io_register_personality(struct io_ring_ctx *ctx)
{
        struct io_identity *id;
        int ret;

        id = kmalloc(sizeof(*id), GFP_KERNEL);
        if (unlikely(!id))
                return -ENOMEM;

        io_init_identity(id);
        id->creds = get_current_cred();

        ret = idr_alloc_cyclic(&ctx->personality_idr, id, 1, USHRT_MAX, GFP_KERNEL);
        if (ret < 0) {
                put_cred(id->creds);
                kfree(id);
        }
        return ret;
}

static int io_unregister_personality(struct io_ring_ctx *ctx, unsigned id)
{
        struct io_identity *iod;

        iod = idr_remove(&ctx->personality_idr, id);
        if (iod) {
                put_cred(iod->creds);
                if (refcount_dec_and_test(&iod->count))
                        kfree(iod);
                return 0;
        }

        return -EINVAL;
}

static int io_register_restrictions(struct io_ring_ctx *ctx, void __user *arg,
                                    unsigned int nr_args)
{
        struct io_uring_restriction *res;
        size_t size;
        int i, ret;

        /* Restrictions allowed only if rings started disabled */
        if (!(ctx->flags & IORING_SETUP_R_DISABLED))
                return -EBADFD;

        /* We allow only a single restrictions registration */
        if (ctx->restrictions.registered)
                return -EBUSY;

        if (!arg || nr_args > IORING_MAX_RESTRICTIONS)
                return -EINVAL;

        size = array_size(nr_args, sizeof(*res));
        if (size == SIZE_MAX)
                return -EOVERFLOW;

        res = memdup_user(arg, size);
        if (IS_ERR(res))
                return PTR_ERR(res);

        ret = 0;

        for (i = 0; i < nr_args; i++) {
                switch (res[i].opcode) {
                case IORING_RESTRICTION_REGISTER_OP:
                        if (res[i].register_op >= IORING_REGISTER_LAST) {
                                ret = -EINVAL;
                                goto out;
                        }

                        __set_bit(res[i].register_op,
                                  ctx->restrictions.register_op);
                        break;
                case IORING_RESTRICTION_SQE_OP:
                        if (res[i].sqe_op >= IORING_OP_LAST) {
                                ret = -EINVAL;
                                goto out;
                        }

                        __set_bit(res[i].sqe_op, ctx->restrictions.sqe_op);
                        break;
                case IORING_RESTRICTION_SQE_FLAGS_ALLOWED:
                        ctx->restrictions.sqe_flags_allowed = res[i].sqe_flags;
                        break;
                case IORING_RESTRICTION_SQE_FLAGS_REQUIRED:
                        ctx->restrictions.sqe_flags_required = res[i].sqe_flags;
                        break;
                default:
                        ret = -EINVAL;
                        goto out;
                }
        }

out:
        /* Reset all restrictions if an error happened */
        if (ret != 0)
                memset(&ctx->restrictions, 0, sizeof(ctx->restrictions));
        else
                ctx->restrictions.registered = true;

        kfree(res);
        return ret;
}

static int io_register_enable_rings(struct io_ring_ctx *ctx)
{
        if (!(ctx->flags & IORING_SETUP_R_DISABLED))
                return -EBADFD;

        if (ctx->restrictions.registered)
                ctx->restricted = 1;

        ctx->flags &= ~IORING_SETUP_R_DISABLED;

        io_sq_offload_start(ctx);

        return 0;
}

static bool io_register_op_must_quiesce(int op)
{
        switch (op) {
        case IORING_UNREGISTER_FILES:
        case IORING_REGISTER_FILES_UPDATE:
        case IORING_REGISTER_PROBE:
        case IORING_REGISTER_PERSONALITY:
        case IORING_UNREGISTER_PERSONALITY:
                return false;
        default:
                return true;
        }
}

static int __io_uring_register(struct io_ring_ctx *ctx, unsigned opcode,
                               void __user *arg, unsigned nr_args)
        __releases(ctx->uring_lock)
        __acquires(ctx->uring_lock)
{
        int ret;

        /*
         * We're inside the ring mutex, if the ref is already dying, then
         * someone else killed the ctx or is already going through
         * io_uring_register().
         */
        if (percpu_ref_is_dying(&ctx->refs))
                return -ENXIO;

        if (io_register_op_must_quiesce(opcode)) {
                percpu_ref_kill(&ctx->refs);

                /*
                 * Drop uring mutex before waiting for references to exit. If
                 * another thread is currently inside io_uring_enter() it might
                 * need to grab the uring_lock to make progress. If we hold it
                 * here across the drain wait, then we can deadlock. It's safe
                 * to drop the mutex here, since no new references will come in
                 * after we've killed the percpu ref.
                 */
                mutex_unlock(&ctx->uring_lock);
                do {
                        ret = wait_for_completion_interruptible(&ctx->ref_comp);
                        if (!ret)
                                break;
                        ret = io_run_task_work_sig();
                        if (ret < 0)
                                break;
                } while (1);

                mutex_lock(&ctx->uring_lock);

                if (ret) {
                        percpu_ref_resurrect(&ctx->refs);
                        goto out_quiesce;
                }
        }

        if (ctx->restricted) {
                if (opcode >= IORING_REGISTER_LAST) {
                        ret = -EINVAL;
                        goto out;
                }

                if (!test_bit(opcode, ctx->restrictions.register_op)) {
                        ret = -EACCES;
                        goto out;
                }
        }

        switch (opcode) {
        case IORING_REGISTER_BUFFERS:
                ret = io_sqe_buffer_register(ctx, arg, nr_args);
                break;
        case IORING_UNREGISTER_BUFFERS:
                ret = -EINVAL;
                if (arg || nr_args)
                        break;
                ret = io_sqe_buffer_unregister(ctx);
                break;
        case IORING_REGISTER_FILES:
                ret = io_sqe_files_register(ctx, arg, nr_args);
                break;
        case IORING_UNREGISTER_FILES:
                ret = -EINVAL;
                if (arg || nr_args)
                        break;
                ret = io_sqe_files_unregister(ctx);
                break;
        case IORING_REGISTER_FILES_UPDATE:
                ret = io_sqe_files_update(ctx, arg, nr_args);
                break;
        case IORING_REGISTER_EVENTFD:
        case IORING_REGISTER_EVENTFD_ASYNC:
                ret = -EINVAL;
                if (nr_args != 1)
                        break;
                ret = io_eventfd_register(ctx, arg);
                if (ret)
                        break;
                if (opcode == IORING_REGISTER_EVENTFD_ASYNC)
                        ctx->eventfd_async = 1;
                else
                        ctx->eventfd_async = 0;
                break;
        case IORING_UNREGISTER_EVENTFD:
                ret = -EINVAL;
                if (arg || nr_args)
                        break;
                ret = io_eventfd_unregister(ctx);
                break;
        case IORING_REGISTER_PROBE:
                ret = -EINVAL;
                if (!arg || nr_args > 256)
                        break;
                ret = io_probe(ctx, arg, nr_args);
                break;
        case IORING_REGISTER_PERSONALITY:
                ret = -EINVAL;
                if (arg || nr_args)
                        break;
                ret = io_register_personality(ctx);
                break;
        case IORING_UNREGISTER_PERSONALITY:
                ret = -EINVAL;
                if (arg)
                        break;
                ret = io_unregister_personality(ctx, nr_args);
                break;
        case IORING_REGISTER_ENABLE_RINGS:
                ret = -EINVAL;
                if (arg || nr_args)
                        break;
                ret = io_register_enable_rings(ctx);
                break;
        case IORING_REGISTER_RESTRICTIONS:
                ret = io_register_restrictions(ctx, arg, nr_args);
                break;
        default:
                ret = -EINVAL;
                break;
        }

out:
        if (io_register_op_must_quiesce(opcode)) {
                /* bring the ctx back to life */
                percpu_ref_reinit(&ctx->refs);
out_quiesce:
                reinit_completion(&ctx->ref_comp);
        }
        return ret;
}

SYSCALL_DEFINE4(io_uring_register, unsigned int, fd, unsigned int, opcode,
                void __user *, arg, unsigned int, nr_args)
{
        struct io_ring_ctx *ctx;
        long ret = -EBADF;
        struct fd f;

        f = fdget(fd);
        if (!f.file)
                return -EBADF;

        ret = -EOPNOTSUPP;
        if (f.file->f_op != &io_uring_fops)
                goto out_fput;

        ctx = f.file->private_data;

        mutex_lock(&ctx->uring_lock);
        ret = __io_uring_register(ctx, opcode, arg, nr_args);
        mutex_unlock(&ctx->uring_lock);
        trace_io_uring_register(ctx, opcode, ctx->nr_user_files, ctx->nr_user_bufs,
                                                        ctx->cq_ev_fd != NULL, ret);
out_fput:
        fdput(f);
        return ret;
}

static int __init io_uring_init(void)
{
#define __BUILD_BUG_VERIFY_ELEMENT(stype, eoffset, etype, ename) do { \
        BUILD_BUG_ON(offsetof(stype, ename) != eoffset); \
        BUILD_BUG_ON(sizeof(etype) != sizeof_field(stype, ename)); \
} while (0)

#define BUILD_BUG_SQE_ELEM(eoffset, etype, ename) \
        __BUILD_BUG_VERIFY_ELEMENT(struct io_uring_sqe, eoffset, etype, ename)
        BUILD_BUG_ON(sizeof(struct io_uring_sqe) != 64);
        BUILD_BUG_SQE_ELEM(0,  __u8,   opcode);
        BUILD_BUG_SQE_ELEM(1,  __u8,   flags);
        BUILD_BUG_SQE_ELEM(2,  __u16,  ioprio);
        BUILD_BUG_SQE_ELEM(4,  __s32,  fd);
        BUILD_BUG_SQE_ELEM(8,  __u64,  off);
        BUILD_BUG_SQE_ELEM(8,  __u64,  addr2);
        BUILD_BUG_SQE_ELEM(16, __u64,  addr);
        BUILD_BUG_SQE_ELEM(16, __u64,  splice_off_in);
        BUILD_BUG_SQE_ELEM(24, __u32,  len);
        BUILD_BUG_SQE_ELEM(28,     __kernel_rwf_t, rw_flags);
        BUILD_BUG_SQE_ELEM(28, /* compat */   int, rw_flags);
        BUILD_BUG_SQE_ELEM(28, /* compat */ __u32, rw_flags);
        BUILD_BUG_SQE_ELEM(28, __u32,  fsync_flags);
        BUILD_BUG_SQE_ELEM(28, /* compat */ __u16,  poll_events);
        BUILD_BUG_SQE_ELEM(28, __u32,  poll32_events);
        BUILD_BUG_SQE_ELEM(28, __u32,  sync_range_flags);
        BUILD_BUG_SQE_ELEM(28, __u32,  msg_flags);
        BUILD_BUG_SQE_ELEM(28, __u32,  timeout_flags);
        BUILD_BUG_SQE_ELEM(28, __u32,  accept_flags);
        BUILD_BUG_SQE_ELEM(28, __u32,  cancel_flags);
        BUILD_BUG_SQE_ELEM(28, __u32,  open_flags);
        BUILD_BUG_SQE_ELEM(28, __u32,  statx_flags);
        BUILD_BUG_SQE_ELEM(28, __u32,  fadvise_advice);
        BUILD_BUG_SQE_ELEM(28, __u32,  splice_flags);
        BUILD_BUG_SQE_ELEM(32, __u64,  user_data);
        BUILD_BUG_SQE_ELEM(40, __u16,  buf_index);
        BUILD_BUG_SQE_ELEM(42, __u16,  personality);
        BUILD_BUG_SQE_ELEM(44, __s32,  splice_fd_in);

        BUILD_BUG_ON(ARRAY_SIZE(io_op_defs) != IORING_OP_LAST);
        BUILD_BUG_ON(__REQ_F_LAST_BIT >= 8 * sizeof(int));
        req_cachep = KMEM_CACHE(io_kiocb, SLAB_HWCACHE_ALIGN | SLAB_PANIC);
        return 0;
};
__initcall(io_uring_init);