net: ethtool: Fix RSS setting

[linux.git] / fs / btrfs / super.c

// SPDX-License-Identifier: GPL-2.0
/*
 * Copyright (C) 2007 Oracle.  All rights reserved.
 */

#include <linux/blkdev.h>
#include <linux/module.h>
#include <linux/fs.h>
#include <linux/pagemap.h>
#include <linux/highmem.h>
#include <linux/time.h>
#include <linux/init.h>
#include <linux/seq_file.h>
#include <linux/string.h>
#include <linux/backing-dev.h>
#include <linux/mount.h>
#include <linux/writeback.h>
#include <linux/statfs.h>
#include <linux/compat.h>
#include <linux/parser.h>
#include <linux/ctype.h>
#include <linux/namei.h>
#include <linux/miscdevice.h>
#include <linux/magic.h>
#include <linux/slab.h>
#include <linux/ratelimit.h>
#include <linux/crc32c.h>
#include <linux/btrfs.h>
#include <linux/security.h>
#include <linux/fs_parser.h>
#include "messages.h"
#include "delayed-inode.h"
#include "ctree.h"
#include "disk-io.h"
#include "transaction.h"
#include "btrfs_inode.h"
#include "props.h"
#include "xattr.h"
#include "bio.h"
#include "export.h"
#include "compression.h"
#include "dev-replace.h"
#include "free-space-cache.h"
#include "backref.h"
#include "space-info.h"
#include "sysfs.h"
#include "zoned.h"
#include "tests/btrfs-tests.h"
#include "block-group.h"
#include "discard.h"
#include "qgroup.h"
#include "raid56.h"
#include "fs.h"
#include "accessors.h"
#include "defrag.h"
#include "dir-item.h"
#include "ioctl.h"
#include "scrub.h"
#include "verity.h"
#include "super.h"
#include "extent-tree.h"
#define CREATE_TRACE_POINTS
#include <trace/events/btrfs.h>

static const struct super_operations btrfs_super_ops;
static struct file_system_type btrfs_fs_type;

static void btrfs_put_super(struct super_block *sb)
{
        struct btrfs_fs_info *fs_info = btrfs_sb(sb);

        btrfs_info(fs_info, "last unmount of filesystem %pU", fs_info->fs_devices->fsid);
        close_ctree(fs_info);
}

/* Store the mount options related information. */
struct btrfs_fs_context {
        char *subvol_name;
        u64 subvol_objectid;
        u64 max_inline;
        u32 commit_interval;
        u32 metadata_ratio;
        u32 thread_pool_size;
        unsigned long mount_opt;
        unsigned long compress_type:4;
        unsigned int compress_level;
        refcount_t refs;
};

enum {
        Opt_acl,
        Opt_clear_cache,
        Opt_commit_interval,
        Opt_compress,
        Opt_compress_force,
        Opt_compress_force_type,
        Opt_compress_type,
        Opt_degraded,
        Opt_device,
        Opt_fatal_errors,
        Opt_flushoncommit,
        Opt_max_inline,
        Opt_barrier,
        Opt_datacow,
        Opt_datasum,
        Opt_defrag,
        Opt_discard,
        Opt_discard_mode,
        Opt_ratio,
        Opt_rescan_uuid_tree,
        Opt_skip_balance,
        Opt_space_cache,
        Opt_space_cache_version,
        Opt_ssd,
        Opt_ssd_spread,
        Opt_subvol,
        Opt_subvol_empty,
        Opt_subvolid,
        Opt_thread_pool,
        Opt_treelog,
        Opt_user_subvol_rm_allowed,
        Opt_norecovery,

        /* Rescue options */
        Opt_rescue,
        Opt_usebackuproot,
        Opt_nologreplay,
        Opt_ignorebadroots,
        Opt_ignoredatacsums,
        Opt_rescue_all,

        /* Debugging options */
        Opt_enospc_debug,
#ifdef CONFIG_BTRFS_DEBUG
        Opt_fragment, Opt_fragment_data, Opt_fragment_metadata, Opt_fragment_all,
#endif
#ifdef CONFIG_BTRFS_FS_REF_VERIFY
        Opt_ref_verify,
#endif
        Opt_err,
};

enum {
        Opt_fatal_errors_panic,
        Opt_fatal_errors_bug,
};

static const struct constant_table btrfs_parameter_fatal_errors[] = {
        { "panic", Opt_fatal_errors_panic },
        { "bug", Opt_fatal_errors_bug },
        {}
};

enum {
        Opt_discard_sync,
        Opt_discard_async,
};

static const struct constant_table btrfs_parameter_discard[] = {
        { "sync", Opt_discard_sync },
        { "async", Opt_discard_async },
        {}
};

enum {
        Opt_space_cache_v1,
        Opt_space_cache_v2,
};

static const struct constant_table btrfs_parameter_space_cache[] = {
        { "v1", Opt_space_cache_v1 },
        { "v2", Opt_space_cache_v2 },
        {}
};

enum {
        Opt_rescue_usebackuproot,
        Opt_rescue_nologreplay,
        Opt_rescue_ignorebadroots,
        Opt_rescue_ignoredatacsums,
        Opt_rescue_parameter_all,
};

static const struct constant_table btrfs_parameter_rescue[] = {
        { "usebackuproot", Opt_rescue_usebackuproot },
        { "nologreplay", Opt_rescue_nologreplay },
        { "ignorebadroots", Opt_rescue_ignorebadroots },
        { "ibadroots", Opt_rescue_ignorebadroots },
        { "ignoredatacsums", Opt_rescue_ignoredatacsums },
        { "idatacsums", Opt_rescue_ignoredatacsums },
        { "all", Opt_rescue_parameter_all },
        {}
};

#ifdef CONFIG_BTRFS_DEBUG
enum {
        Opt_fragment_parameter_data,
        Opt_fragment_parameter_metadata,
        Opt_fragment_parameter_all,
};

static const struct constant_table btrfs_parameter_fragment[] = {
        { "data", Opt_fragment_parameter_data },
        { "metadata", Opt_fragment_parameter_metadata },
        { "all", Opt_fragment_parameter_all },
        {}
};
#endif

static const struct fs_parameter_spec btrfs_fs_parameters[] = {
        fsparam_flag_no("acl", Opt_acl),
        fsparam_flag_no("autodefrag", Opt_defrag),
        fsparam_flag_no("barrier", Opt_barrier),
        fsparam_flag("clear_cache", Opt_clear_cache),
        fsparam_u32("commit", Opt_commit_interval),
        fsparam_flag("compress", Opt_compress),
        fsparam_string("compress", Opt_compress_type),
        fsparam_flag("compress-force", Opt_compress_force),
        fsparam_string("compress-force", Opt_compress_force_type),
        fsparam_flag_no("datacow", Opt_datacow),
        fsparam_flag_no("datasum", Opt_datasum),
        fsparam_flag("degraded", Opt_degraded),
        fsparam_string("device", Opt_device),
        fsparam_flag_no("discard", Opt_discard),
        fsparam_enum("discard", Opt_discard_mode, btrfs_parameter_discard),
        fsparam_enum("fatal_errors", Opt_fatal_errors, btrfs_parameter_fatal_errors),
        fsparam_flag_no("flushoncommit", Opt_flushoncommit),
        fsparam_string("max_inline", Opt_max_inline),
        fsparam_u32("metadata_ratio", Opt_ratio),
        fsparam_flag("rescan_uuid_tree", Opt_rescan_uuid_tree),
        fsparam_flag("skip_balance", Opt_skip_balance),
        fsparam_flag_no("space_cache", Opt_space_cache),
        fsparam_enum("space_cache", Opt_space_cache_version, btrfs_parameter_space_cache),
        fsparam_flag_no("ssd", Opt_ssd),
        fsparam_flag_no("ssd_spread", Opt_ssd_spread),
        fsparam_string("subvol", Opt_subvol),
        fsparam_flag("subvol=", Opt_subvol_empty),
        fsparam_u64("subvolid", Opt_subvolid),
        fsparam_u32("thread_pool", Opt_thread_pool),
        fsparam_flag_no("treelog", Opt_treelog),
        fsparam_flag("user_subvol_rm_allowed", Opt_user_subvol_rm_allowed),

        /* Rescue options. */
        fsparam_enum("rescue", Opt_rescue, btrfs_parameter_rescue),
        /* Deprecated, with alias rescue=nologreplay */
        __fsparam(NULL, "nologreplay", Opt_nologreplay, fs_param_deprecated, NULL),
        /* Deprecated, with alias rescue=usebackuproot */
        __fsparam(NULL, "usebackuproot", Opt_usebackuproot, fs_param_deprecated, NULL),
        /* For compatibility only, alias for "rescue=nologreplay". */
        fsparam_flag("norecovery", Opt_norecovery),

        /* Debugging options. */
        fsparam_flag_no("enospc_debug", Opt_enospc_debug),
#ifdef CONFIG_BTRFS_DEBUG
        fsparam_enum("fragment", Opt_fragment, btrfs_parameter_fragment),
#endif
#ifdef CONFIG_BTRFS_FS_REF_VERIFY
        fsparam_flag("ref_verify", Opt_ref_verify),
#endif
        {}
};

/* No support for restricting writes to btrfs devices yet... */
static inline blk_mode_t btrfs_open_mode(struct fs_context *fc)
{
        return sb_open_mode(fc->sb_flags) & ~BLK_OPEN_RESTRICT_WRITES;
}

static int btrfs_parse_param(struct fs_context *fc, struct fs_parameter *param)
{
        struct btrfs_fs_context *ctx = fc->fs_private;
        struct fs_parse_result result;
        int opt;

        opt = fs_parse(fc, btrfs_fs_parameters, param, &result);
        if (opt < 0)
                return opt;

        switch (opt) {
        case Opt_degraded:
                btrfs_set_opt(ctx->mount_opt, DEGRADED);
                break;
        case Opt_subvol_empty:
                /*
                 * This exists because we used to allow it on accident, so we're
                 * keeping it to maintain ABI.  See 37becec95ac3 ("Btrfs: allow
                 * empty subvol= again").
                 */
                break;
        case Opt_subvol:
                kfree(ctx->subvol_name);
                ctx->subvol_name = kstrdup(param->string, GFP_KERNEL);
                if (!ctx->subvol_name)
                        return -ENOMEM;
                break;
        case Opt_subvolid:
                ctx->subvol_objectid = result.uint_64;

                /* subvolid=0 means give me the original fs_tree. */
                if (!ctx->subvol_objectid)
                        ctx->subvol_objectid = BTRFS_FS_TREE_OBJECTID;
                break;
        case Opt_device: {
                struct btrfs_device *device;
                blk_mode_t mode = btrfs_open_mode(fc);

                mutex_lock(&uuid_mutex);
                device = btrfs_scan_one_device(param->string, mode, false);
                mutex_unlock(&uuid_mutex);
                if (IS_ERR(device))
                        return PTR_ERR(device);
                break;
        }
        case Opt_datasum:
                if (result.negated) {
                        btrfs_set_opt(ctx->mount_opt, NODATASUM);
                } else {
                        btrfs_clear_opt(ctx->mount_opt, NODATACOW);
                        btrfs_clear_opt(ctx->mount_opt, NODATASUM);
                }
                break;
        case Opt_datacow:
                if (result.negated) {
                        btrfs_clear_opt(ctx->mount_opt, COMPRESS);
                        btrfs_clear_opt(ctx->mount_opt, FORCE_COMPRESS);
                        btrfs_set_opt(ctx->mount_opt, NODATACOW);
                        btrfs_set_opt(ctx->mount_opt, NODATASUM);
                } else {
                        btrfs_clear_opt(ctx->mount_opt, NODATACOW);
                }
                break;
        case Opt_compress_force:
        case Opt_compress_force_type:
                btrfs_set_opt(ctx->mount_opt, FORCE_COMPRESS);
                fallthrough;
        case Opt_compress:
        case Opt_compress_type:
                if (opt == Opt_compress || opt == Opt_compress_force) {
                        ctx->compress_type = BTRFS_COMPRESS_ZLIB;
                        ctx->compress_level = BTRFS_ZLIB_DEFAULT_LEVEL;
                        btrfs_set_opt(ctx->mount_opt, COMPRESS);
                        btrfs_clear_opt(ctx->mount_opt, NODATACOW);
                        btrfs_clear_opt(ctx->mount_opt, NODATASUM);
                } else if (strncmp(param->string, "zlib", 4) == 0) {
                        ctx->compress_type = BTRFS_COMPRESS_ZLIB;
                        ctx->compress_level =
                                btrfs_compress_str2level(BTRFS_COMPRESS_ZLIB,
                                                         param->string + 4);
                        btrfs_set_opt(ctx->mount_opt, COMPRESS);
                        btrfs_clear_opt(ctx->mount_opt, NODATACOW);
                        btrfs_clear_opt(ctx->mount_opt, NODATASUM);
                } else if (strncmp(param->string, "lzo", 3) == 0) {
                        ctx->compress_type = BTRFS_COMPRESS_LZO;
                        ctx->compress_level = 0;
                        btrfs_set_opt(ctx->mount_opt, COMPRESS);
                        btrfs_clear_opt(ctx->mount_opt, NODATACOW);
                        btrfs_clear_opt(ctx->mount_opt, NODATASUM);
                } else if (strncmp(param->string, "zstd", 4) == 0) {
                        ctx->compress_type = BTRFS_COMPRESS_ZSTD;
                        ctx->compress_level =
                                btrfs_compress_str2level(BTRFS_COMPRESS_ZSTD,
                                                         param->string + 4);
                        btrfs_set_opt(ctx->mount_opt, COMPRESS);
                        btrfs_clear_opt(ctx->mount_opt, NODATACOW);
                        btrfs_clear_opt(ctx->mount_opt, NODATASUM);
                } else if (strncmp(param->string, "no", 2) == 0) {
                        ctx->compress_level = 0;
                        ctx->compress_type = 0;
                        btrfs_clear_opt(ctx->mount_opt, COMPRESS);
                        btrfs_clear_opt(ctx->mount_opt, FORCE_COMPRESS);
                } else {
                        btrfs_err(NULL, "unrecognized compression value %s",
                                  param->string);
                        return -EINVAL;
                }
                break;
        case Opt_ssd:
                if (result.negated) {
                        btrfs_set_opt(ctx->mount_opt, NOSSD);
                        btrfs_clear_opt(ctx->mount_opt, SSD);
                        btrfs_clear_opt(ctx->mount_opt, SSD_SPREAD);
                } else {
                        btrfs_set_opt(ctx->mount_opt, SSD);
                        btrfs_clear_opt(ctx->mount_opt, NOSSD);
                }
                break;
        case Opt_ssd_spread:
                if (result.negated) {
                        btrfs_clear_opt(ctx->mount_opt, SSD_SPREAD);
                } else {
                        btrfs_set_opt(ctx->mount_opt, SSD);
                        btrfs_set_opt(ctx->mount_opt, SSD_SPREAD);
                        btrfs_clear_opt(ctx->mount_opt, NOSSD);
                }
                break;
        case Opt_barrier:
                if (result.negated)
                        btrfs_set_opt(ctx->mount_opt, NOBARRIER);
                else
                        btrfs_clear_opt(ctx->mount_opt, NOBARRIER);
                break;
        case Opt_thread_pool:
                if (result.uint_32 == 0) {
                        btrfs_err(NULL, "invalid value 0 for thread_pool");
                        return -EINVAL;
                }
                ctx->thread_pool_size = result.uint_32;
                break;
        case Opt_max_inline:
                ctx->max_inline = memparse(param->string, NULL);
                break;
        case Opt_acl:
                if (result.negated) {
                        fc->sb_flags &= ~SB_POSIXACL;
                } else {
#ifdef CONFIG_BTRFS_FS_POSIX_ACL
                        fc->sb_flags |= SB_POSIXACL;
#else
                        btrfs_err(NULL, "support for ACL not compiled in");
                        return -EINVAL;
#endif
                }
                /*
                 * VFS limits the ability to toggle ACL on and off via remount,
                 * despite every file system allowing this.  This seems to be
                 * an oversight since we all do, but it'll fail if we're
                 * remounting.  So don't set the mask here, we'll check it in
                 * btrfs_reconfigure and do the toggling ourselves.
                 */
                if (fc->purpose != FS_CONTEXT_FOR_RECONFIGURE)
                        fc->sb_flags_mask |= SB_POSIXACL;
                break;
        case Opt_treelog:
                if (result.negated)
                        btrfs_set_opt(ctx->mount_opt, NOTREELOG);
                else
                        btrfs_clear_opt(ctx->mount_opt, NOTREELOG);
                break;
        case Opt_nologreplay:
                btrfs_warn(NULL,
                "'nologreplay' is deprecated, use 'rescue=nologreplay' instead");
                btrfs_set_opt(ctx->mount_opt, NOLOGREPLAY);
                break;
        case Opt_norecovery:
                btrfs_info(NULL,
"'norecovery' is for compatibility only, recommended to use 'rescue=nologreplay'");
                btrfs_set_opt(ctx->mount_opt, NOLOGREPLAY);
                break;
        case Opt_flushoncommit:
                if (result.negated)
                        btrfs_clear_opt(ctx->mount_opt, FLUSHONCOMMIT);
                else
                        btrfs_set_opt(ctx->mount_opt, FLUSHONCOMMIT);
                break;
        case Opt_ratio:
                ctx->metadata_ratio = result.uint_32;
                break;
        case Opt_discard:
                if (result.negated) {
                        btrfs_clear_opt(ctx->mount_opt, DISCARD_SYNC);
                        btrfs_clear_opt(ctx->mount_opt, DISCARD_ASYNC);
                        btrfs_set_opt(ctx->mount_opt, NODISCARD);
                } else {
                        btrfs_set_opt(ctx->mount_opt, DISCARD_SYNC);
                        btrfs_clear_opt(ctx->mount_opt, DISCARD_ASYNC);
                }
                break;
        case Opt_discard_mode:
                switch (result.uint_32) {
                case Opt_discard_sync:
                        btrfs_clear_opt(ctx->mount_opt, DISCARD_ASYNC);
                        btrfs_set_opt(ctx->mount_opt, DISCARD_SYNC);
                        break;
                case Opt_discard_async:
                        btrfs_clear_opt(ctx->mount_opt, DISCARD_SYNC);
                        btrfs_set_opt(ctx->mount_opt, DISCARD_ASYNC);
                        break;
                default:
                        btrfs_err(NULL, "unrecognized discard mode value %s",
                                  param->key);
                        return -EINVAL;
                }
                btrfs_clear_opt(ctx->mount_opt, NODISCARD);
                break;
        case Opt_space_cache:
                if (result.negated) {
                        btrfs_set_opt(ctx->mount_opt, NOSPACECACHE);
                        btrfs_clear_opt(ctx->mount_opt, SPACE_CACHE);
                        btrfs_clear_opt(ctx->mount_opt, FREE_SPACE_TREE);
                } else {
                        btrfs_clear_opt(ctx->mount_opt, FREE_SPACE_TREE);
                        btrfs_set_opt(ctx->mount_opt, SPACE_CACHE);
                }
                break;
        case Opt_space_cache_version:
                switch (result.uint_32) {
                case Opt_space_cache_v1:
                        btrfs_set_opt(ctx->mount_opt, SPACE_CACHE);
                        btrfs_clear_opt(ctx->mount_opt, FREE_SPACE_TREE);
                        break;
                case Opt_space_cache_v2:
                        btrfs_clear_opt(ctx->mount_opt, SPACE_CACHE);
                        btrfs_set_opt(ctx->mount_opt, FREE_SPACE_TREE);
                        break;
                default:
                        btrfs_err(NULL, "unrecognized space_cache value %s",
                                  param->key);
                        return -EINVAL;
                }
                break;
        case Opt_rescan_uuid_tree:
                btrfs_set_opt(ctx->mount_opt, RESCAN_UUID_TREE);
                break;
        case Opt_clear_cache:
                btrfs_set_opt(ctx->mount_opt, CLEAR_CACHE);
                break;
        case Opt_user_subvol_rm_allowed:
                btrfs_set_opt(ctx->mount_opt, USER_SUBVOL_RM_ALLOWED);
                break;
        case Opt_enospc_debug:
                if (result.negated)
                        btrfs_clear_opt(ctx->mount_opt, ENOSPC_DEBUG);
                else
                        btrfs_set_opt(ctx->mount_opt, ENOSPC_DEBUG);
                break;
        case Opt_defrag:
                if (result.negated)
                        btrfs_clear_opt(ctx->mount_opt, AUTO_DEFRAG);
                else
                        btrfs_set_opt(ctx->mount_opt, AUTO_DEFRAG);
                break;
        case Opt_usebackuproot:
                btrfs_warn(NULL,
                           "'usebackuproot' is deprecated, use 'rescue=usebackuproot' instead");
                btrfs_set_opt(ctx->mount_opt, USEBACKUPROOT);

                /* If we're loading the backup roots we can't trust the space cache. */
                btrfs_set_opt(ctx->mount_opt, CLEAR_CACHE);
                break;
        case Opt_skip_balance:
                btrfs_set_opt(ctx->mount_opt, SKIP_BALANCE);
                break;
        case Opt_fatal_errors:
                switch (result.uint_32) {
                case Opt_fatal_errors_panic:
                        btrfs_set_opt(ctx->mount_opt, PANIC_ON_FATAL_ERROR);
                        break;
                case Opt_fatal_errors_bug:
                        btrfs_clear_opt(ctx->mount_opt, PANIC_ON_FATAL_ERROR);
                        break;
                default:
                        btrfs_err(NULL, "unrecognized fatal_errors value %s",
                                  param->key);
                        return -EINVAL;
                }
                break;
        case Opt_commit_interval:
                ctx->commit_interval = result.uint_32;
                if (ctx->commit_interval == 0)
                        ctx->commit_interval = BTRFS_DEFAULT_COMMIT_INTERVAL;
                break;
        case Opt_rescue:
                switch (result.uint_32) {
                case Opt_rescue_usebackuproot:
                        btrfs_set_opt(ctx->mount_opt, USEBACKUPROOT);
                        break;
                case Opt_rescue_nologreplay:
                        btrfs_set_opt(ctx->mount_opt, NOLOGREPLAY);
                        break;
                case Opt_rescue_ignorebadroots:
                        btrfs_set_opt(ctx->mount_opt, IGNOREBADROOTS);
                        break;
                case Opt_rescue_ignoredatacsums:
                        btrfs_set_opt(ctx->mount_opt, IGNOREDATACSUMS);
                        break;
                case Opt_rescue_parameter_all:
                        btrfs_set_opt(ctx->mount_opt, IGNOREDATACSUMS);
                        btrfs_set_opt(ctx->mount_opt, IGNOREBADROOTS);
                        btrfs_set_opt(ctx->mount_opt, NOLOGREPLAY);
                        break;
                default:
                        btrfs_info(NULL, "unrecognized rescue option '%s'",
                                   param->key);
                        return -EINVAL;
                }
                break;
#ifdef CONFIG_BTRFS_DEBUG
        case Opt_fragment:
                switch (result.uint_32) {
                case Opt_fragment_parameter_all:
                        btrfs_set_opt(ctx->mount_opt, FRAGMENT_DATA);
                        btrfs_set_opt(ctx->mount_opt, FRAGMENT_METADATA);
                        break;
                case Opt_fragment_parameter_metadata:
                        btrfs_set_opt(ctx->mount_opt, FRAGMENT_METADATA);
                        break;
                case Opt_fragment_parameter_data:
                        btrfs_set_opt(ctx->mount_opt, FRAGMENT_DATA);
                        break;
                default:
                        btrfs_info(NULL, "unrecognized fragment option '%s'",
                                   param->key);
                        return -EINVAL;
                }
                break;
#endif
#ifdef CONFIG_BTRFS_FS_REF_VERIFY
        case Opt_ref_verify:
                btrfs_set_opt(ctx->mount_opt, REF_VERIFY);
                break;
#endif
        default:
                btrfs_err(NULL, "unrecognized mount option '%s'", param->key);
                return -EINVAL;
        }

        return 0;
}

/*
 * Some options only have meaning at mount time and shouldn't persist across
 * remounts, or be displayed. Clear these at the end of mount and remount code
 * paths.
 */
static void btrfs_clear_oneshot_options(struct btrfs_fs_info *fs_info)
{
        btrfs_clear_opt(fs_info->mount_opt, USEBACKUPROOT);
        btrfs_clear_opt(fs_info->mount_opt, CLEAR_CACHE);
        btrfs_clear_opt(fs_info->mount_opt, NOSPACECACHE);
}

static bool check_ro_option(struct btrfs_fs_info *fs_info,
                            unsigned long mount_opt, unsigned long opt,
                            const char *opt_name)
{
        if (mount_opt & opt) {
                btrfs_err(fs_info, "%s must be used with ro mount option",
                          opt_name);
                return true;
        }
        return false;
}

bool btrfs_check_options(struct btrfs_fs_info *info, unsigned long *mount_opt,
                         unsigned long flags)
{
        bool ret = true;

        if (!(flags & SB_RDONLY) &&
            (check_ro_option(info, *mount_opt, BTRFS_MOUNT_NOLOGREPLAY, "nologreplay") ||
             check_ro_option(info, *mount_opt, BTRFS_MOUNT_IGNOREBADROOTS, "ignorebadroots") ||
             check_ro_option(info, *mount_opt, BTRFS_MOUNT_IGNOREDATACSUMS, "ignoredatacsums")))
                ret = false;

        if (btrfs_fs_compat_ro(info, FREE_SPACE_TREE) &&
            !btrfs_raw_test_opt(*mount_opt, FREE_SPACE_TREE) &&
            !btrfs_raw_test_opt(*mount_opt, CLEAR_CACHE)) {
                btrfs_err(info, "cannot disable free-space-tree");
                ret = false;
        }
        if (btrfs_fs_compat_ro(info, BLOCK_GROUP_TREE) &&
             !btrfs_raw_test_opt(*mount_opt, FREE_SPACE_TREE)) {
                btrfs_err(info, "cannot disable free-space-tree with block-group-tree feature");
                ret = false;
        }

        if (btrfs_check_mountopts_zoned(info, mount_opt))
                ret = false;

        if (!test_bit(BTRFS_FS_STATE_REMOUNTING, &info->fs_state)) {
                if (btrfs_raw_test_opt(*mount_opt, SPACE_CACHE))
                        btrfs_info(info, "disk space caching is enabled");
                if (btrfs_raw_test_opt(*mount_opt, FREE_SPACE_TREE))
                        btrfs_info(info, "using free-space-tree");
        }

        return ret;
}

/*
 * This is subtle, we only call this during open_ctree().  We need to pre-load
 * the mount options with the on-disk settings.  Before the new mount API took
 * effect we would do this on mount and remount.  With the new mount API we'll
 * only do this on the initial mount.
 *
 * This isn't a change in behavior, because we're using the current state of the
 * file system to set the current mount options.  If you mounted with special
 * options to disable these features and then remounted we wouldn't revert the
 * settings, because mounting without these features cleared the on-disk
 * settings, so this being called on re-mount is not needed.
 */
void btrfs_set_free_space_cache_settings(struct btrfs_fs_info *fs_info)
{
        if (fs_info->sectorsize < PAGE_SIZE) {
                btrfs_clear_opt(fs_info->mount_opt, SPACE_CACHE);
                if (!btrfs_test_opt(fs_info, FREE_SPACE_TREE)) {
                        btrfs_info(fs_info,
                                   "forcing free space tree for sector size %u with page size %lu",
                                   fs_info->sectorsize, PAGE_SIZE);
                        btrfs_set_opt(fs_info->mount_opt, FREE_SPACE_TREE);
                }
        }

        /*
         * At this point our mount options are populated, so we only mess with
         * these settings if we don't have any settings already.
         */
        if (btrfs_test_opt(fs_info, FREE_SPACE_TREE))
                return;

        if (btrfs_is_zoned(fs_info) &&
            btrfs_free_space_cache_v1_active(fs_info)) {
                btrfs_info(fs_info, "zoned: clearing existing space cache");
                btrfs_set_super_cache_generation(fs_info->super_copy, 0);
                return;
        }

        if (btrfs_test_opt(fs_info, SPACE_CACHE))
                return;

        if (btrfs_test_opt(fs_info, NOSPACECACHE))
                return;

        /*
         * At this point we don't have explicit options set by the user, set
         * them ourselves based on the state of the file system.
         */
        if (btrfs_fs_compat_ro(fs_info, FREE_SPACE_TREE))
                btrfs_set_opt(fs_info->mount_opt, FREE_SPACE_TREE);
        else if (btrfs_free_space_cache_v1_active(fs_info))
                btrfs_set_opt(fs_info->mount_opt, SPACE_CACHE);
}

static void set_device_specific_options(struct btrfs_fs_info *fs_info)
{
        if (!btrfs_test_opt(fs_info, NOSSD) &&
            !fs_info->fs_devices->rotating)
                btrfs_set_opt(fs_info->mount_opt, SSD);

        /*
         * For devices supporting discard turn on discard=async automatically,
         * unless it's already set or disabled. This could be turned off by
         * nodiscard for the same mount.
         *
         * The zoned mode piggy backs on the discard functionality for
         * resetting a zone. There is no reason to delay the zone reset as it is
         * fast enough. So, do not enable async discard for zoned mode.
         */
        if (!(btrfs_test_opt(fs_info, DISCARD_SYNC) ||
              btrfs_test_opt(fs_info, DISCARD_ASYNC) ||
              btrfs_test_opt(fs_info, NODISCARD)) &&
            fs_info->fs_devices->discardable &&
            !btrfs_is_zoned(fs_info))
                btrfs_set_opt(fs_info->mount_opt, DISCARD_ASYNC);
}

char *btrfs_get_subvol_name_from_objectid(struct btrfs_fs_info *fs_info,
                                          u64 subvol_objectid)
{
        struct btrfs_root *root = fs_info->tree_root;
        struct btrfs_root *fs_root = NULL;
        struct btrfs_root_ref *root_ref;
        struct btrfs_inode_ref *inode_ref;
        struct btrfs_key key;
        struct btrfs_path *path = NULL;
        char *name = NULL, *ptr;
        u64 dirid;
        int len;
        int ret;

        path = btrfs_alloc_path();
        if (!path) {
                ret = -ENOMEM;
                goto err;
        }

        name = kmalloc(PATH_MAX, GFP_KERNEL);
        if (!name) {
                ret = -ENOMEM;
                goto err;
        }
        ptr = name + PATH_MAX - 1;
        ptr[0] = '\0';

        /*
         * Walk up the subvolume trees in the tree of tree roots by root
         * backrefs until we hit the top-level subvolume.
         */
        while (subvol_objectid != BTRFS_FS_TREE_OBJECTID) {
                key.objectid = subvol_objectid;
                key.type = BTRFS_ROOT_BACKREF_KEY;
                key.offset = (u64)-1;

                ret = btrfs_search_backwards(root, &key, path);
                if (ret < 0) {
                        goto err;
                } else if (ret > 0) {
                        ret = -ENOENT;
                        goto err;
                }

                subvol_objectid = key.offset;

                root_ref = btrfs_item_ptr(path->nodes[0], path->slots[0],
                                          struct btrfs_root_ref);
                len = btrfs_root_ref_name_len(path->nodes[0], root_ref);
                ptr -= len + 1;
                if (ptr < name) {
                        ret = -ENAMETOOLONG;
                        goto err;
                }
                read_extent_buffer(path->nodes[0], ptr + 1,
                                   (unsigned long)(root_ref + 1), len);
                ptr[0] = '/';
                dirid = btrfs_root_ref_dirid(path->nodes[0], root_ref);
                btrfs_release_path(path);

                fs_root = btrfs_get_fs_root(fs_info, subvol_objectid, true);
                if (IS_ERR(fs_root)) {
                        ret = PTR_ERR(fs_root);
                        fs_root = NULL;
                        goto err;
                }

                /*
                 * Walk up the filesystem tree by inode refs until we hit the
                 * root directory.
                 */
                while (dirid != BTRFS_FIRST_FREE_OBJECTID) {
                        key.objectid = dirid;
                        key.type = BTRFS_INODE_REF_KEY;
                        key.offset = (u64)-1;

                        ret = btrfs_search_backwards(fs_root, &key, path);
                        if (ret < 0) {
                                goto err;
                        } else if (ret > 0) {
                                ret = -ENOENT;
                                goto err;
                        }

                        dirid = key.offset;

                        inode_ref = btrfs_item_ptr(path->nodes[0],
                                                   path->slots[0],
                                                   struct btrfs_inode_ref);
                        len = btrfs_inode_ref_name_len(path->nodes[0],
                                                       inode_ref);
                        ptr -= len + 1;
                        if (ptr < name) {
                                ret = -ENAMETOOLONG;
                                goto err;
                        }
                        read_extent_buffer(path->nodes[0], ptr + 1,
                                           (unsigned long)(inode_ref + 1), len);
                        ptr[0] = '/';
                        btrfs_release_path(path);
                }
                btrfs_put_root(fs_root);
                fs_root = NULL;
        }

        btrfs_free_path(path);
        if (ptr == name + PATH_MAX - 1) {
                name[0] = '/';
                name[1] = '\0';
        } else {
                memmove(name, ptr, name + PATH_MAX - ptr);
        }
        return name;

err:
        btrfs_put_root(fs_root);
        btrfs_free_path(path);
        kfree(name);
        return ERR_PTR(ret);
}

static int get_default_subvol_objectid(struct btrfs_fs_info *fs_info, u64 *objectid)
{
        struct btrfs_root *root = fs_info->tree_root;
        struct btrfs_dir_item *di;
        struct btrfs_path *path;
        struct btrfs_key location;
        struct fscrypt_str name = FSTR_INIT("default", 7);
        u64 dir_id;

        path = btrfs_alloc_path();
        if (!path)
                return -ENOMEM;

        /*
         * Find the "default" dir item which points to the root item that we
         * will mount by default if we haven't been given a specific subvolume
         * to mount.
         */
        dir_id = btrfs_super_root_dir(fs_info->super_copy);
        di = btrfs_lookup_dir_item(NULL, root, path, dir_id, &name, 0);
        if (IS_ERR(di)) {
                btrfs_free_path(path);
                return PTR_ERR(di);
        }
        if (!di) {
                /*
                 * Ok the default dir item isn't there.  This is weird since
                 * it's always been there, but don't freak out, just try and
                 * mount the top-level subvolume.
                 */
                btrfs_free_path(path);
                *objectid = BTRFS_FS_TREE_OBJECTID;
                return 0;
        }

        btrfs_dir_item_key_to_cpu(path->nodes[0], di, &location);
        btrfs_free_path(path);
        *objectid = location.objectid;
        return 0;
}

static int btrfs_fill_super(struct super_block *sb,
                            struct btrfs_fs_devices *fs_devices,
                            void *data)
{
        struct inode *inode;
        struct btrfs_fs_info *fs_info = btrfs_sb(sb);
        int err;

        sb->s_maxbytes = MAX_LFS_FILESIZE;
        sb->s_magic = BTRFS_SUPER_MAGIC;
        sb->s_op = &btrfs_super_ops;
        sb->s_d_op = &btrfs_dentry_operations;
        sb->s_export_op = &btrfs_export_ops;
#ifdef CONFIG_FS_VERITY
        sb->s_vop = &btrfs_verityops;
#endif
        sb->s_xattr = btrfs_xattr_handlers;
        sb->s_time_gran = 1;
        sb->s_iflags |= SB_I_CGROUPWB;

        err = super_setup_bdi(sb);
        if (err) {
                btrfs_err(fs_info, "super_setup_bdi failed");
                return err;
        }

        err = open_ctree(sb, fs_devices, (char *)data);
        if (err) {
                btrfs_err(fs_info, "open_ctree failed");
                return err;
        }

        inode = btrfs_iget(sb, BTRFS_FIRST_FREE_OBJECTID, fs_info->fs_root);
        if (IS_ERR(inode)) {
                err = PTR_ERR(inode);
                btrfs_handle_fs_error(fs_info, err, NULL);
                goto fail_close;
        }

        sb->s_root = d_make_root(inode);
        if (!sb->s_root) {
                err = -ENOMEM;
                goto fail_close;
        }

        sb->s_flags |= SB_ACTIVE;
        return 0;

fail_close:
        close_ctree(fs_info);
        return err;
}

int btrfs_sync_fs(struct super_block *sb, int wait)
{
        struct btrfs_trans_handle *trans;
        struct btrfs_fs_info *fs_info = btrfs_sb(sb);
        struct btrfs_root *root = fs_info->tree_root;

        trace_btrfs_sync_fs(fs_info, wait);

        if (!wait) {
                filemap_flush(fs_info->btree_inode->i_mapping);
                return 0;
        }

        btrfs_wait_ordered_roots(fs_info, U64_MAX, 0, (u64)-1);

        trans = btrfs_attach_transaction_barrier(root);
        if (IS_ERR(trans)) {
                /* no transaction, don't bother */
                if (PTR_ERR(trans) == -ENOENT) {
                        /*
                         * Exit unless we have some pending changes
                         * that need to go through commit
                         */
                        if (!test_bit(BTRFS_FS_NEED_TRANS_COMMIT,
                                      &fs_info->flags))
                                return 0;
                        /*
                         * A non-blocking test if the fs is frozen. We must not
                         * start a new transaction here otherwise a deadlock
                         * happens. The pending operations are delayed to the
                         * next commit after thawing.
                         */
                        if (sb_start_write_trylock(sb))
                                sb_end_write(sb);
                        else
                                return 0;
                        trans = btrfs_start_transaction(root, 0);
                }
                if (IS_ERR(trans))
                        return PTR_ERR(trans);
        }
        return btrfs_commit_transaction(trans);
}

static void print_rescue_option(struct seq_file *seq, const char *s, bool *printed)
{
        seq_printf(seq, "%s%s", (*printed) ? ":" : ",rescue=", s);
        *printed = true;
}

static int btrfs_show_options(struct seq_file *seq, struct dentry *dentry)
{
        struct btrfs_fs_info *info = btrfs_sb(dentry->d_sb);
        const char *compress_type;
        const char *subvol_name;
        bool printed = false;

        if (btrfs_test_opt(info, DEGRADED))
                seq_puts(seq, ",degraded");
        if (btrfs_test_opt(info, NODATASUM))
                seq_puts(seq, ",nodatasum");
        if (btrfs_test_opt(info, NODATACOW))
                seq_puts(seq, ",nodatacow");
        if (btrfs_test_opt(info, NOBARRIER))
                seq_puts(seq, ",nobarrier");
        if (info->max_inline != BTRFS_DEFAULT_MAX_INLINE)
                seq_printf(seq, ",max_inline=%llu", info->max_inline);
        if (info->thread_pool_size !=  min_t(unsigned long,
                                             num_online_cpus() + 2, 8))
                seq_printf(seq, ",thread_pool=%u", info->thread_pool_size);
        if (btrfs_test_opt(info, COMPRESS)) {
                compress_type = btrfs_compress_type2str(info->compress_type);
                if (btrfs_test_opt(info, FORCE_COMPRESS))
                        seq_printf(seq, ",compress-force=%s", compress_type);
                else
                        seq_printf(seq, ",compress=%s", compress_type);
                if (info->compress_level)
                        seq_printf(seq, ":%d", info->compress_level);
        }
        if (btrfs_test_opt(info, NOSSD))
                seq_puts(seq, ",nossd");
        if (btrfs_test_opt(info, SSD_SPREAD))
                seq_puts(seq, ",ssd_spread");
        else if (btrfs_test_opt(info, SSD))
                seq_puts(seq, ",ssd");
        if (btrfs_test_opt(info, NOTREELOG))
                seq_puts(seq, ",notreelog");
        if (btrfs_test_opt(info, NOLOGREPLAY))
                print_rescue_option(seq, "nologreplay", &printed);
        if (btrfs_test_opt(info, USEBACKUPROOT))
                print_rescue_option(seq, "usebackuproot", &printed);
        if (btrfs_test_opt(info, IGNOREBADROOTS))
                print_rescue_option(seq, "ignorebadroots", &printed);
        if (btrfs_test_opt(info, IGNOREDATACSUMS))
                print_rescue_option(seq, "ignoredatacsums", &printed);
        if (btrfs_test_opt(info, FLUSHONCOMMIT))
                seq_puts(seq, ",flushoncommit");
        if (btrfs_test_opt(info, DISCARD_SYNC))
                seq_puts(seq, ",discard");
        if (btrfs_test_opt(info, DISCARD_ASYNC))
                seq_puts(seq, ",discard=async");
        if (!(info->sb->s_flags & SB_POSIXACL))
                seq_puts(seq, ",noacl");
        if (btrfs_free_space_cache_v1_active(info))
                seq_puts(seq, ",space_cache");
        else if (btrfs_fs_compat_ro(info, FREE_SPACE_TREE))
                seq_puts(seq, ",space_cache=v2");
        else
                seq_puts(seq, ",nospace_cache");
        if (btrfs_test_opt(info, RESCAN_UUID_TREE))
                seq_puts(seq, ",rescan_uuid_tree");
        if (btrfs_test_opt(info, CLEAR_CACHE))
                seq_puts(seq, ",clear_cache");
        if (btrfs_test_opt(info, USER_SUBVOL_RM_ALLOWED))
                seq_puts(seq, ",user_subvol_rm_allowed");
        if (btrfs_test_opt(info, ENOSPC_DEBUG))
                seq_puts(seq, ",enospc_debug");
        if (btrfs_test_opt(info, AUTO_DEFRAG))
                seq_puts(seq, ",autodefrag");
        if (btrfs_test_opt(info, SKIP_BALANCE))
                seq_puts(seq, ",skip_balance");
        if (info->metadata_ratio)
                seq_printf(seq, ",metadata_ratio=%u", info->metadata_ratio);
        if (btrfs_test_opt(info, PANIC_ON_FATAL_ERROR))
                seq_puts(seq, ",fatal_errors=panic");
        if (info->commit_interval != BTRFS_DEFAULT_COMMIT_INTERVAL)
                seq_printf(seq, ",commit=%u", info->commit_interval);
#ifdef CONFIG_BTRFS_DEBUG
        if (btrfs_test_opt(info, FRAGMENT_DATA))
                seq_puts(seq, ",fragment=data");
        if (btrfs_test_opt(info, FRAGMENT_METADATA))
                seq_puts(seq, ",fragment=metadata");
#endif
        if (btrfs_test_opt(info, REF_VERIFY))
                seq_puts(seq, ",ref_verify");
        seq_printf(seq, ",subvolid=%llu", btrfs_root_id(BTRFS_I(d_inode(dentry))->root));
        subvol_name = btrfs_get_subvol_name_from_objectid(info,
                        btrfs_root_id(BTRFS_I(d_inode(dentry))->root));
        if (!IS_ERR(subvol_name)) {
                seq_puts(seq, ",subvol=");
                seq_escape(seq, subvol_name, " \t\n\\");
                kfree(subvol_name);
        }
        return 0;
}

/*
 * subvolumes are identified by ino 256
 */
static inline int is_subvolume_inode(struct inode *inode)
{
        if (inode && inode->i_ino == BTRFS_FIRST_FREE_OBJECTID)
                return 1;
        return 0;
}

static struct dentry *mount_subvol(const char *subvol_name, u64 subvol_objectid,
                                   struct vfsmount *mnt)
{
        struct dentry *root;
        int ret;

        if (!subvol_name) {
                if (!subvol_objectid) {
                        ret = get_default_subvol_objectid(btrfs_sb(mnt->mnt_sb),
                                                          &subvol_objectid);
                        if (ret) {
                                root = ERR_PTR(ret);
                                goto out;
                        }
                }
                subvol_name = btrfs_get_subvol_name_from_objectid(
                                        btrfs_sb(mnt->mnt_sb), subvol_objectid);
                if (IS_ERR(subvol_name)) {
                        root = ERR_CAST(subvol_name);
                        subvol_name = NULL;
                        goto out;
                }

        }

        root = mount_subtree(mnt, subvol_name);
        /* mount_subtree() drops our reference on the vfsmount. */
        mnt = NULL;

        if (!IS_ERR(root)) {
                struct super_block *s = root->d_sb;
                struct btrfs_fs_info *fs_info = btrfs_sb(s);
                struct inode *root_inode = d_inode(root);
                u64 root_objectid = btrfs_root_id(BTRFS_I(root_inode)->root);

                ret = 0;
                if (!is_subvolume_inode(root_inode)) {
                        btrfs_err(fs_info, "'%s' is not a valid subvolume",
                               subvol_name);
                        ret = -EINVAL;
                }
                if (subvol_objectid && root_objectid != subvol_objectid) {
                        /*
                         * This will also catch a race condition where a
                         * subvolume which was passed by ID is renamed and
                         * another subvolume is renamed over the old location.
                         */
                        btrfs_err(fs_info,
                                  "subvol '%s' does not match subvolid %llu",
                                  subvol_name, subvol_objectid);
                        ret = -EINVAL;
                }
                if (ret) {
                        dput(root);
                        root = ERR_PTR(ret);
                        deactivate_locked_super(s);
                }
        }

out:
        mntput(mnt);
        kfree(subvol_name);
        return root;
}

static void btrfs_resize_thread_pool(struct btrfs_fs_info *fs_info,
                                     u32 new_pool_size, u32 old_pool_size)
{
        if (new_pool_size == old_pool_size)
                return;

        fs_info->thread_pool_size = new_pool_size;

        btrfs_info(fs_info, "resize thread pool %d -> %d",
               old_pool_size, new_pool_size);

        btrfs_workqueue_set_max(fs_info->workers, new_pool_size);
        btrfs_workqueue_set_max(fs_info->delalloc_workers, new_pool_size);
        btrfs_workqueue_set_max(fs_info->caching_workers, new_pool_size);
        workqueue_set_max_active(fs_info->endio_workers, new_pool_size);
        workqueue_set_max_active(fs_info->endio_meta_workers, new_pool_size);
        btrfs_workqueue_set_max(fs_info->endio_write_workers, new_pool_size);
        btrfs_workqueue_set_max(fs_info->endio_freespace_worker, new_pool_size);
        btrfs_workqueue_set_max(fs_info->delayed_workers, new_pool_size);
}

static inline void btrfs_remount_begin(struct btrfs_fs_info *fs_info,
                                       unsigned long old_opts, int flags)
{
        if (btrfs_raw_test_opt(old_opts, AUTO_DEFRAG) &&
            (!btrfs_raw_test_opt(fs_info->mount_opt, AUTO_DEFRAG) ||
             (flags & SB_RDONLY))) {
                /* wait for any defraggers to finish */
                wait_event(fs_info->transaction_wait,
                           (atomic_read(&fs_info->defrag_running) == 0));
                if (flags & SB_RDONLY)
                        sync_filesystem(fs_info->sb);
        }
}

static inline void btrfs_remount_cleanup(struct btrfs_fs_info *fs_info,
                                         unsigned long old_opts)
{
        const bool cache_opt = btrfs_test_opt(fs_info, SPACE_CACHE);

        /*
         * We need to cleanup all defragable inodes if the autodefragment is
         * close or the filesystem is read only.
         */
        if (btrfs_raw_test_opt(old_opts, AUTO_DEFRAG) &&
            (!btrfs_raw_test_opt(fs_info->mount_opt, AUTO_DEFRAG) || sb_rdonly(fs_info->sb))) {
                btrfs_cleanup_defrag_inodes(fs_info);
        }

        /* If we toggled discard async */
        if (!btrfs_raw_test_opt(old_opts, DISCARD_ASYNC) &&
            btrfs_test_opt(fs_info, DISCARD_ASYNC))
                btrfs_discard_resume(fs_info);
        else if (btrfs_raw_test_opt(old_opts, DISCARD_ASYNC) &&
                 !btrfs_test_opt(fs_info, DISCARD_ASYNC))
                btrfs_discard_cleanup(fs_info);

        /* If we toggled space cache */
        if (cache_opt != btrfs_free_space_cache_v1_active(fs_info))
                btrfs_set_free_space_cache_v1_active(fs_info, cache_opt);
}

static int btrfs_remount_rw(struct btrfs_fs_info *fs_info)
{
        int ret;

        if (BTRFS_FS_ERROR(fs_info)) {
                btrfs_err(fs_info,
                          "remounting read-write after error is not allowed");
                return -EINVAL;
        }

        if (fs_info->fs_devices->rw_devices == 0)
                return -EACCES;

        if (!btrfs_check_rw_degradable(fs_info, NULL)) {
                btrfs_warn(fs_info,
                           "too many missing devices, writable remount is not allowed");
                return -EACCES;
        }

        if (btrfs_super_log_root(fs_info->super_copy) != 0) {
                btrfs_warn(fs_info,
                           "mount required to replay tree-log, cannot remount read-write");
                return -EINVAL;
        }

        /*
         * NOTE: when remounting with a change that does writes, don't put it
         * anywhere above this point, as we are not sure to be safe to write
         * until we pass the above checks.
         */
        ret = btrfs_start_pre_rw_mount(fs_info);
        if (ret)
                return ret;

        btrfs_clear_sb_rdonly(fs_info->sb);

        set_bit(BTRFS_FS_OPEN, &fs_info->flags);

        /*
         * If we've gone from readonly -> read-write, we need to get our
         * sync/async discard lists in the right state.
         */
        btrfs_discard_resume(fs_info);

        return 0;
}

static int btrfs_remount_ro(struct btrfs_fs_info *fs_info)
{
        /*
         * This also happens on 'umount -rf' or on shutdown, when the
         * filesystem is busy.
         */
        cancel_work_sync(&fs_info->async_reclaim_work);
        cancel_work_sync(&fs_info->async_data_reclaim_work);

        btrfs_discard_cleanup(fs_info);

        /* Wait for the uuid_scan task to finish */
        down(&fs_info->uuid_tree_rescan_sem);
        /* Avoid complains from lockdep et al. */
        up(&fs_info->uuid_tree_rescan_sem);

        btrfs_set_sb_rdonly(fs_info->sb);

        /*
         * Setting SB_RDONLY will put the cleaner thread to sleep at the next
         * loop if it's already active.  If it's already asleep, we'll leave
         * unused block groups on disk until we're mounted read-write again
         * unless we clean them up here.
         */
        btrfs_delete_unused_bgs(fs_info);

        /*
         * The cleaner task could be already running before we set the flag
         * BTRFS_FS_STATE_RO (and SB_RDONLY in the superblock).  We must make
         * sure that after we finish the remount, i.e. after we call
         * btrfs_commit_super(), the cleaner can no longer start a transaction
         * - either because it was dropping a dead root, running delayed iputs
         *   or deleting an unused block group (the cleaner picked a block
         *   group from the list of unused block groups before we were able to
         *   in the previous call to btrfs_delete_unused_bgs()).
         */
        wait_on_bit(&fs_info->flags, BTRFS_FS_CLEANER_RUNNING, TASK_UNINTERRUPTIBLE);

        /*
         * We've set the superblock to RO mode, so we might have made the
         * cleaner task sleep without running all pending delayed iputs. Go
         * through all the delayed iputs here, so that if an unmount happens
         * without remounting RW we don't end up at finishing close_ctree()
         * with a non-empty list of delayed iputs.
         */
        btrfs_run_delayed_iputs(fs_info);

        btrfs_dev_replace_suspend_for_unmount(fs_info);
        btrfs_scrub_cancel(fs_info);
        btrfs_pause_balance(fs_info);

        /*
         * Pause the qgroup rescan worker if it is running. We don't want it to
         * be still running after we are in RO mode, as after that, by the time
         * we unmount, it might have left a transaction open, so we would leak
         * the transaction and/or crash.
         */
        btrfs_qgroup_wait_for_completion(fs_info, false);

        return btrfs_commit_super(fs_info);
}

static void btrfs_ctx_to_info(struct btrfs_fs_info *fs_info, struct btrfs_fs_context *ctx)
{
        fs_info->max_inline = ctx->max_inline;
        fs_info->commit_interval = ctx->commit_interval;
        fs_info->metadata_ratio = ctx->metadata_ratio;
        fs_info->thread_pool_size = ctx->thread_pool_size;
        fs_info->mount_opt = ctx->mount_opt;
        fs_info->compress_type = ctx->compress_type;
        fs_info->compress_level = ctx->compress_level;
}

static void btrfs_info_to_ctx(struct btrfs_fs_info *fs_info, struct btrfs_fs_context *ctx)
{
        ctx->max_inline = fs_info->max_inline;
        ctx->commit_interval = fs_info->commit_interval;
        ctx->metadata_ratio = fs_info->metadata_ratio;
        ctx->thread_pool_size = fs_info->thread_pool_size;
        ctx->mount_opt = fs_info->mount_opt;
        ctx->compress_type = fs_info->compress_type;
        ctx->compress_level = fs_info->compress_level;
}

#define btrfs_info_if_set(fs_info, old_ctx, opt, fmt, args...)                  \
do {                                                                            \
        if ((!old_ctx || !btrfs_raw_test_opt(old_ctx->mount_opt, opt)) &&       \
            btrfs_raw_test_opt(fs_info->mount_opt, opt))                        \
                btrfs_info(fs_info, fmt, ##args);                               \
} while (0)

#define btrfs_info_if_unset(fs_info, old_ctx, opt, fmt, args...)        \
do {                                                                    \
        if ((old_ctx && btrfs_raw_test_opt(old_ctx->mount_opt, opt)) && \
            !btrfs_raw_test_opt(fs_info->mount_opt, opt))               \
                btrfs_info(fs_info, fmt, ##args);                       \
} while (0)

static void btrfs_emit_options(struct btrfs_fs_info *info,
                               struct btrfs_fs_context *old)
{
        btrfs_info_if_set(info, old, NODATASUM, "setting nodatasum");
        btrfs_info_if_set(info, old, DEGRADED, "allowing degraded mounts");
        btrfs_info_if_set(info, old, NODATASUM, "setting nodatasum");
        btrfs_info_if_set(info, old, SSD, "enabling ssd optimizations");
        btrfs_info_if_set(info, old, SSD_SPREAD, "using spread ssd allocation scheme");
        btrfs_info_if_set(info, old, NOBARRIER, "turning off barriers");
        btrfs_info_if_set(info, old, NOTREELOG, "disabling tree log");
        btrfs_info_if_set(info, old, NOLOGREPLAY, "disabling log replay at mount time");
        btrfs_info_if_set(info, old, FLUSHONCOMMIT, "turning on flush-on-commit");
        btrfs_info_if_set(info, old, DISCARD_SYNC, "turning on sync discard");
        btrfs_info_if_set(info, old, DISCARD_ASYNC, "turning on async discard");
        btrfs_info_if_set(info, old, FREE_SPACE_TREE, "enabling free space tree");
        btrfs_info_if_set(info, old, SPACE_CACHE, "enabling disk space caching");
        btrfs_info_if_set(info, old, CLEAR_CACHE, "force clearing of disk cache");
        btrfs_info_if_set(info, old, AUTO_DEFRAG, "enabling auto defrag");
        btrfs_info_if_set(info, old, FRAGMENT_DATA, "fragmenting data");
        btrfs_info_if_set(info, old, FRAGMENT_METADATA, "fragmenting metadata");
        btrfs_info_if_set(info, old, REF_VERIFY, "doing ref verification");
        btrfs_info_if_set(info, old, USEBACKUPROOT, "trying to use backup root at mount time");
        btrfs_info_if_set(info, old, IGNOREBADROOTS, "ignoring bad roots");
        btrfs_info_if_set(info, old, IGNOREDATACSUMS, "ignoring data csums");

        btrfs_info_if_unset(info, old, NODATACOW, "setting datacow");
        btrfs_info_if_unset(info, old, SSD, "not using ssd optimizations");
        btrfs_info_if_unset(info, old, SSD_SPREAD, "not using spread ssd allocation scheme");
        btrfs_info_if_unset(info, old, NOBARRIER, "turning off barriers");
        btrfs_info_if_unset(info, old, NOTREELOG, "enabling tree log");
        btrfs_info_if_unset(info, old, SPACE_CACHE, "disabling disk space caching");
        btrfs_info_if_unset(info, old, FREE_SPACE_TREE, "disabling free space tree");
        btrfs_info_if_unset(info, old, AUTO_DEFRAG, "disabling auto defrag");
        btrfs_info_if_unset(info, old, COMPRESS, "use no compression");

        /* Did the compression settings change? */
        if (btrfs_test_opt(info, COMPRESS) &&
            (!old ||
             old->compress_type != info->compress_type ||
             old->compress_level != info->compress_level ||
             (!btrfs_raw_test_opt(old->mount_opt, FORCE_COMPRESS) &&
              btrfs_raw_test_opt(info->mount_opt, FORCE_COMPRESS)))) {
                const char *compress_type = btrfs_compress_type2str(info->compress_type);

                btrfs_info(info, "%s %s compression, level %d",
                           btrfs_test_opt(info, FORCE_COMPRESS) ? "force" : "use",
                           compress_type, info->compress_level);
        }

        if (info->max_inline != BTRFS_DEFAULT_MAX_INLINE)
                btrfs_info(info, "max_inline set to %llu", info->max_inline);
}

static int btrfs_reconfigure(struct fs_context *fc)
{
        struct super_block *sb = fc->root->d_sb;
        struct btrfs_fs_info *fs_info = btrfs_sb(sb);
        struct btrfs_fs_context *ctx = fc->fs_private;
        struct btrfs_fs_context old_ctx;
        int ret = 0;
        bool mount_reconfigure = (fc->s_fs_info != NULL);

        btrfs_info_to_ctx(fs_info, &old_ctx);

        /*
         * This is our "bind mount" trick, we don't want to allow the user to do
         * anything other than mount a different ro/rw and a different subvol,
         * all of the mount options should be maintained.
         */
        if (mount_reconfigure)
                ctx->mount_opt = old_ctx.mount_opt;

        sync_filesystem(sb);
        set_bit(BTRFS_FS_STATE_REMOUNTING, &fs_info->fs_state);

        if (!mount_reconfigure &&
            !btrfs_check_options(fs_info, &ctx->mount_opt, fc->sb_flags))
                return -EINVAL;

        ret = btrfs_check_features(fs_info, !(fc->sb_flags & SB_RDONLY));
        if (ret < 0)
                return ret;

        btrfs_ctx_to_info(fs_info, ctx);
        btrfs_remount_begin(fs_info, old_ctx.mount_opt, fc->sb_flags);
        btrfs_resize_thread_pool(fs_info, fs_info->thread_pool_size,
                                 old_ctx.thread_pool_size);

        if ((bool)btrfs_test_opt(fs_info, FREE_SPACE_TREE) !=
            (bool)btrfs_fs_compat_ro(fs_info, FREE_SPACE_TREE) &&
            (!sb_rdonly(sb) || (fc->sb_flags & SB_RDONLY))) {
                btrfs_warn(fs_info,
                "remount supports changing free space tree only from RO to RW");
                /* Make sure free space cache options match the state on disk. */
                if (btrfs_fs_compat_ro(fs_info, FREE_SPACE_TREE)) {
                        btrfs_set_opt(fs_info->mount_opt, FREE_SPACE_TREE);
                        btrfs_clear_opt(fs_info->mount_opt, SPACE_CACHE);
                }
                if (btrfs_free_space_cache_v1_active(fs_info)) {
                        btrfs_clear_opt(fs_info->mount_opt, FREE_SPACE_TREE);
                        btrfs_set_opt(fs_info->mount_opt, SPACE_CACHE);
                }
        }

        ret = 0;
        if (!sb_rdonly(sb) && (fc->sb_flags & SB_RDONLY))
                ret = btrfs_remount_ro(fs_info);
        else if (sb_rdonly(sb) && !(fc->sb_flags & SB_RDONLY))
                ret = btrfs_remount_rw(fs_info);
        if (ret)
                goto restore;

        /*
         * If we set the mask during the parameter parsing VFS would reject the
         * remount.  Here we can set the mask and the value will be updated
         * appropriately.
         */
        if ((fc->sb_flags & SB_POSIXACL) != (sb->s_flags & SB_POSIXACL))
                fc->sb_flags_mask |= SB_POSIXACL;

        btrfs_emit_options(fs_info, &old_ctx);
        wake_up_process(fs_info->transaction_kthread);
        btrfs_remount_cleanup(fs_info, old_ctx.mount_opt);
        btrfs_clear_oneshot_options(fs_info);
        clear_bit(BTRFS_FS_STATE_REMOUNTING, &fs_info->fs_state);

        return 0;
restore:
        btrfs_ctx_to_info(fs_info, &old_ctx);
        btrfs_remount_cleanup(fs_info, old_ctx.mount_opt);
        clear_bit(BTRFS_FS_STATE_REMOUNTING, &fs_info->fs_state);
        return ret;
}

/* Used to sort the devices by max_avail(descending sort) */
static int btrfs_cmp_device_free_bytes(const void *a, const void *b)
{
        const struct btrfs_device_info *dev_info1 = a;
        const struct btrfs_device_info *dev_info2 = b;

        if (dev_info1->max_avail > dev_info2->max_avail)
                return -1;
        else if (dev_info1->max_avail < dev_info2->max_avail)
                return 1;
        return 0;
}

/*
 * sort the devices by max_avail, in which max free extent size of each device
 * is stored.(Descending Sort)
 */
static inline void btrfs_descending_sort_devices(
                                        struct btrfs_device_info *devices,
                                        size_t nr_devices)
{
        sort(devices, nr_devices, sizeof(struct btrfs_device_info),
             btrfs_cmp_device_free_bytes, NULL);
}

/*
 * The helper to calc the free space on the devices that can be used to store
 * file data.
 */
static inline int btrfs_calc_avail_data_space(struct btrfs_fs_info *fs_info,
                                              u64 *free_bytes)
{
        struct btrfs_device_info *devices_info;
        struct btrfs_fs_devices *fs_devices = fs_info->fs_devices;
        struct btrfs_device *device;
        u64 type;
        u64 avail_space;
        u64 min_stripe_size;
        int num_stripes = 1;
        int i = 0, nr_devices;
        const struct btrfs_raid_attr *rattr;

        /*
         * We aren't under the device list lock, so this is racy-ish, but good
         * enough for our purposes.
         */
        nr_devices = fs_info->fs_devices->open_devices;
        if (!nr_devices) {
                smp_mb();
                nr_devices = fs_info->fs_devices->open_devices;
                ASSERT(nr_devices);
                if (!nr_devices) {
                        *free_bytes = 0;
                        return 0;
                }
        }

        devices_info = kmalloc_array(nr_devices, sizeof(*devices_info),
                               GFP_KERNEL);
        if (!devices_info)
                return -ENOMEM;

        /* calc min stripe number for data space allocation */
        type = btrfs_data_alloc_profile(fs_info);
        rattr = &btrfs_raid_array[btrfs_bg_flags_to_raid_index(type)];

        if (type & BTRFS_BLOCK_GROUP_RAID0)
                num_stripes = nr_devices;
        else if (type & BTRFS_BLOCK_GROUP_RAID1_MASK)
                num_stripes = rattr->ncopies;
        else if (type & BTRFS_BLOCK_GROUP_RAID10)
                num_stripes = 4;

        /* Adjust for more than 1 stripe per device */
        min_stripe_size = rattr->dev_stripes * BTRFS_STRIPE_LEN;

        rcu_read_lock();
        list_for_each_entry_rcu(device, &fs_devices->devices, dev_list) {
                if (!test_bit(BTRFS_DEV_STATE_IN_FS_METADATA,
                                                &device->dev_state) ||
                    !device->bdev ||
                    test_bit(BTRFS_DEV_STATE_REPLACE_TGT, &device->dev_state))
                        continue;

                if (i >= nr_devices)
                        break;

                avail_space = device->total_bytes - device->bytes_used;

                /* align with stripe_len */
                avail_space = rounddown(avail_space, BTRFS_STRIPE_LEN);

                /*
                 * Ensure we have at least min_stripe_size on top of the
                 * reserved space on the device.
                 */
                if (avail_space <= BTRFS_DEVICE_RANGE_RESERVED + min_stripe_size)
                        continue;

                avail_space -= BTRFS_DEVICE_RANGE_RESERVED;

                devices_info[i].dev = device;
                devices_info[i].max_avail = avail_space;

                i++;
        }
        rcu_read_unlock();

        nr_devices = i;

        btrfs_descending_sort_devices(devices_info, nr_devices);

        i = nr_devices - 1;
        avail_space = 0;
        while (nr_devices >= rattr->devs_min) {
                num_stripes = min(num_stripes, nr_devices);

                if (devices_info[i].max_avail >= min_stripe_size) {
                        int j;
                        u64 alloc_size;

                        avail_space += devices_info[i].max_avail * num_stripes;
                        alloc_size = devices_info[i].max_avail;
                        for (j = i + 1 - num_stripes; j <= i; j++)
                                devices_info[j].max_avail -= alloc_size;
                }
                i--;
                nr_devices--;
        }

        kfree(devices_info);
        *free_bytes = avail_space;
        return 0;
}

/*
 * Calculate numbers for 'df', pessimistic in case of mixed raid profiles.
 *
 * If there's a redundant raid level at DATA block groups, use the respective
 * multiplier to scale the sizes.
 *
 * Unused device space usage is based on simulating the chunk allocator
 * algorithm that respects the device sizes and order of allocations.  This is
 * a close approximation of the actual use but there are other factors that may
 * change the result (like a new metadata chunk).
 *
 * If metadata is exhausted, f_bavail will be 0.
 */
static int btrfs_statfs(struct dentry *dentry, struct kstatfs *buf)
{
        struct btrfs_fs_info *fs_info = btrfs_sb(dentry->d_sb);
        struct btrfs_super_block *disk_super = fs_info->super_copy;
        struct btrfs_space_info *found;
        u64 total_used = 0;
        u64 total_free_data = 0;
        u64 total_free_meta = 0;
        u32 bits = fs_info->sectorsize_bits;
        __be32 *fsid = (__be32 *)fs_info->fs_devices->fsid;
        unsigned factor = 1;
        struct btrfs_block_rsv *block_rsv = &fs_info->global_block_rsv;
        int ret;
        u64 thresh = 0;
        int mixed = 0;

        list_for_each_entry(found, &fs_info->space_info, list) {
                if (found->flags & BTRFS_BLOCK_GROUP_DATA) {
                        int i;

                        total_free_data += found->disk_total - found->disk_used;
                        total_free_data -=
                                btrfs_account_ro_block_groups_free_space(found);

                        for (i = 0; i < BTRFS_NR_RAID_TYPES; i++) {
                                if (!list_empty(&found->block_groups[i]))
                                        factor = btrfs_bg_type_to_factor(
                                                btrfs_raid_array[i].bg_flag);
                        }
                }

                /*
                 * Metadata in mixed block group profiles are accounted in data
                 */
                if (!mixed && found->flags & BTRFS_BLOCK_GROUP_METADATA) {
                        if (found->flags & BTRFS_BLOCK_GROUP_DATA)
                                mixed = 1;
                        else
                                total_free_meta += found->disk_total -
                                        found->disk_used;
                }

                total_used += found->disk_used;
        }

        buf->f_blocks = div_u64(btrfs_super_total_bytes(disk_super), factor);
        buf->f_blocks >>= bits;
        buf->f_bfree = buf->f_blocks - (div_u64(total_used, factor) >> bits);

        /* Account global block reserve as used, it's in logical size already */
        spin_lock(&block_rsv->lock);
        /* Mixed block groups accounting is not byte-accurate, avoid overflow */
        if (buf->f_bfree >= block_rsv->size >> bits)
                buf->f_bfree -= block_rsv->size >> bits;
        else
                buf->f_bfree = 0;
        spin_unlock(&block_rsv->lock);

        buf->f_bavail = div_u64(total_free_data, factor);
        ret = btrfs_calc_avail_data_space(fs_info, &total_free_data);
        if (ret)
                return ret;
        buf->f_bavail += div_u64(total_free_data, factor);
        buf->f_bavail = buf->f_bavail >> bits;

        /*
         * We calculate the remaining metadata space minus global reserve. If
         * this is (supposedly) smaller than zero, there's no space. But this
         * does not hold in practice, the exhausted state happens where's still
         * some positive delta. So we apply some guesswork and compare the
         * delta to a 4M threshold.  (Practically observed delta was ~2M.)
         *
         * We probably cannot calculate the exact threshold value because this
         * depends on the internal reservations requested by various
         * operations, so some operations that consume a few metadata will
         * succeed even if the Avail is zero. But this is better than the other
         * way around.
         */
        thresh = SZ_4M;

        /*
         * We only want to claim there's no available space if we can no longer
         * allocate chunks for our metadata profile and our global reserve will
         * not fit in the free metadata space.  If we aren't ->full then we
         * still can allocate chunks and thus are fine using the currently
         * calculated f_bavail.
         */
        if (!mixed && block_rsv->space_info->full &&
            (total_free_meta < thresh || total_free_meta - thresh < block_rsv->size))
                buf->f_bavail = 0;

        buf->f_type = BTRFS_SUPER_MAGIC;
        buf->f_bsize = fs_info->sectorsize;
        buf->f_namelen = BTRFS_NAME_LEN;

        /* We treat it as constant endianness (it doesn't matter _which_)
           because we want the fsid to come out the same whether mounted
           on a big-endian or little-endian host */
        buf->f_fsid.val[0] = be32_to_cpu(fsid[0]) ^ be32_to_cpu(fsid[2]);
        buf->f_fsid.val[1] = be32_to_cpu(fsid[1]) ^ be32_to_cpu(fsid[3]);
        /* Mask in the root object ID too, to disambiguate subvols */
        buf->f_fsid.val[0] ^= btrfs_root_id(BTRFS_I(d_inode(dentry))->root) >> 32;
        buf->f_fsid.val[1] ^= btrfs_root_id(BTRFS_I(d_inode(dentry))->root);

        return 0;
}

static int btrfs_fc_test_super(struct super_block *sb, struct fs_context *fc)
{
        struct btrfs_fs_info *p = fc->s_fs_info;
        struct btrfs_fs_info *fs_info = btrfs_sb(sb);

        return fs_info->fs_devices == p->fs_devices;
}

static int btrfs_get_tree_super(struct fs_context *fc)
{
        struct btrfs_fs_info *fs_info = fc->s_fs_info;
        struct btrfs_fs_context *ctx = fc->fs_private;
        struct btrfs_fs_devices *fs_devices = NULL;
        struct block_device *bdev;
        struct btrfs_device *device;
        struct super_block *sb;
        blk_mode_t mode = btrfs_open_mode(fc);
        int ret;

        btrfs_ctx_to_info(fs_info, ctx);
        mutex_lock(&uuid_mutex);

        /*
         * With 'true' passed to btrfs_scan_one_device() (mount time) we expect
         * either a valid device or an error.
         */
        device = btrfs_scan_one_device(fc->source, mode, true);
        ASSERT(device != NULL);
        if (IS_ERR(device)) {
                mutex_unlock(&uuid_mutex);
                return PTR_ERR(device);
        }

        fs_devices = device->fs_devices;
        fs_info->fs_devices = fs_devices;

        ret = btrfs_open_devices(fs_devices, mode, &btrfs_fs_type);
        mutex_unlock(&uuid_mutex);
        if (ret)
                return ret;

        if (!(fc->sb_flags & SB_RDONLY) && fs_devices->rw_devices == 0) {
                ret = -EACCES;
                goto error;
        }

        bdev = fs_devices->latest_dev->bdev;

        /*
         * From now on the error handling is not straightforward.
         *
         * If successful, this will transfer the fs_info into the super block,
         * and fc->s_fs_info will be NULL.  However if there's an existing
         * super, we'll still have fc->s_fs_info populated.  If we error
         * completely out it'll be cleaned up when we drop the fs_context,
         * otherwise it's tied to the lifetime of the super_block.
         */
        sb = sget_fc(fc, btrfs_fc_test_super, set_anon_super_fc);
        if (IS_ERR(sb)) {
                ret = PTR_ERR(sb);
                goto error;
        }

        set_device_specific_options(fs_info);

        if (sb->s_root) {
                btrfs_close_devices(fs_devices);
                if ((fc->sb_flags ^ sb->s_flags) & SB_RDONLY)
                        ret = -EBUSY;
        } else {
                snprintf(sb->s_id, sizeof(sb->s_id), "%pg", bdev);
                shrinker_debugfs_rename(sb->s_shrink, "sb-btrfs:%s", sb->s_id);
                btrfs_sb(sb)->bdev_holder = &btrfs_fs_type;
                ret = btrfs_fill_super(sb, fs_devices, NULL);
        }

        if (ret) {
                deactivate_locked_super(sb);
                return ret;
        }

        btrfs_clear_oneshot_options(fs_info);

        fc->root = dget(sb->s_root);
        return 0;

error:
        btrfs_close_devices(fs_devices);
        return ret;
}

/*
 * Ever since commit 0723a0473fb4 ("btrfs: allow mounting btrfs subvolumes
 * with different ro/rw options") the following works:
 *
 *        (i) mount /dev/sda3 -o subvol=foo,ro /mnt/foo
 *       (ii) mount /dev/sda3 -o subvol=bar,rw /mnt/bar
 *
 * which looks nice and innocent but is actually pretty intricate and deserves
 * a long comment.
 *
 * On another filesystem a subvolume mount is close to something like:
 *
 *      (iii) # create rw superblock + initial mount
 *            mount -t xfs /dev/sdb /opt/
 *
 *            # create ro bind mount
 *            mount --bind -o ro /opt/foo /mnt/foo
 *
 *            # unmount initial mount
 *            umount /opt
 *
 * Of course, there's some special subvolume sauce and there's the fact that the
 * sb->s_root dentry is really swapped after mount_subtree(). But conceptually
 * it's very close and will help us understand the issue.
 *
 * The old mount API didn't cleanly distinguish between a mount being made ro
 * and a superblock being made ro.  The only way to change the ro state of
 * either object was by passing ms_rdonly. If a new mount was created via
 * mount(2) such as:
 *
 *      mount("/dev/sdb", "/mnt", "xfs", ms_rdonly, null);
 *
 * the MS_RDONLY flag being specified had two effects:
 *
 * (1) MNT_READONLY was raised -> the resulting mount got
 *     @mnt->mnt_flags |= MNT_READONLY raised.
 *
 * (2) MS_RDONLY was passed to the filesystem's mount method and the filesystems
 *     made the superblock ro. Note, how SB_RDONLY has the same value as
 *     ms_rdonly and is raised whenever MS_RDONLY is passed through mount(2).
 *
 * Creating a subtree mount via (iii) ends up leaving a rw superblock with a
 * subtree mounted ro.
 *
 * But consider the effect on the old mount API on btrfs subvolume mounting
 * which combines the distinct step in (iii) into a single step.
 *
 * By issuing (i) both the mount and the superblock are turned ro. Now when (ii)
 * is issued the superblock is ro and thus even if the mount created for (ii) is
 * rw it wouldn't help. Hence, btrfs needed to transition the superblock from ro
 * to rw for (ii) which it did using an internal remount call.
 *
 * IOW, subvolume mounting was inherently complicated due to the ambiguity of
 * MS_RDONLY in mount(2). Note, this ambiguity has mount(8) always translate
 * "ro" to MS_RDONLY. IOW, in both (i) and (ii) "ro" becomes MS_RDONLY when
 * passed by mount(8) to mount(2).
 *
 * Enter the new mount API. The new mount API disambiguates making a mount ro
 * and making a superblock ro.
 *
 * (3) To turn a mount ro the MOUNT_ATTR_ONLY flag can be used with either
 *     fsmount() or mount_setattr() this is a pure VFS level change for a
 *     specific mount or mount tree that is never seen by the filesystem itself.
 *
 * (4) To turn a superblock ro the "ro" flag must be used with
 *     fsconfig(FSCONFIG_SET_FLAG, "ro"). This option is seen by the filesystem
 *     in fc->sb_flags.
 *
 * This disambiguation has rather positive consequences.  Mounting a subvolume
 * ro will not also turn the superblock ro. Only the mount for the subvolume
 * will become ro.
 *
 * So, if the superblock creation request comes from the new mount API the
 * caller must have explicitly done:
 *
 *      fsconfig(FSCONFIG_SET_FLAG, "ro")
 *      fsmount/mount_setattr(MOUNT_ATTR_RDONLY)
 *
 * IOW, at some point the caller must have explicitly turned the whole
 * superblock ro and we shouldn't just undo it like we did for the old mount
 * API. In any case, it lets us avoid the hack in the new mount API.
 *
 * Consequently, the remounting hack must only be used for requests originating
 * from the old mount API and should be marked for full deprecation so it can be
 * turned off in a couple of years.
 *
 * The new mount API has no reason to support this hack.
 */
static struct vfsmount *btrfs_reconfigure_for_mount(struct fs_context *fc)
{
        struct vfsmount *mnt;
        int ret;
        const bool ro2rw = !(fc->sb_flags & SB_RDONLY);

        /*
         * We got an EBUSY because our SB_RDONLY flag didn't match the existing
         * super block, so invert our setting here and retry the mount so we
         * can get our vfsmount.
         */
        if (ro2rw)
                fc->sb_flags |= SB_RDONLY;
        else
                fc->sb_flags &= ~SB_RDONLY;

        mnt = fc_mount(fc);
        if (IS_ERR(mnt))
                return mnt;

        if (!fc->oldapi || !ro2rw)
                return mnt;

        /* We need to convert to rw, call reconfigure. */
        fc->sb_flags &= ~SB_RDONLY;
        down_write(&mnt->mnt_sb->s_umount);
        ret = btrfs_reconfigure(fc);
        up_write(&mnt->mnt_sb->s_umount);
        if (ret) {
                mntput(mnt);
                return ERR_PTR(ret);
        }
        return mnt;
}

static int btrfs_get_tree_subvol(struct fs_context *fc)
{
        struct btrfs_fs_info *fs_info = NULL;
        struct btrfs_fs_context *ctx = fc->fs_private;
        struct fs_context *dup_fc;
        struct dentry *dentry;
        struct vfsmount *mnt;

        /*
         * Setup a dummy root and fs_info for test/set super.  This is because
         * we don't actually fill this stuff out until open_ctree, but we need
         * then open_ctree will properly initialize the file system specific
         * settings later.  btrfs_init_fs_info initializes the static elements
         * of the fs_info (locks and such) to make cleanup easier if we find a
         * superblock with our given fs_devices later on at sget() time.
         */
        fs_info = kvzalloc(sizeof(struct btrfs_fs_info), GFP_KERNEL);
        if (!fs_info)
                return -ENOMEM;

        fs_info->super_copy = kzalloc(BTRFS_SUPER_INFO_SIZE, GFP_KERNEL);
        fs_info->super_for_commit = kzalloc(BTRFS_SUPER_INFO_SIZE, GFP_KERNEL);
        if (!fs_info->super_copy || !fs_info->super_for_commit) {
                btrfs_free_fs_info(fs_info);
                return -ENOMEM;
        }
        btrfs_init_fs_info(fs_info);

        dup_fc = vfs_dup_fs_context(fc);
        if (IS_ERR(dup_fc)) {
                btrfs_free_fs_info(fs_info);
                return PTR_ERR(dup_fc);
        }

        /*
         * When we do the sget_fc this gets transferred to the sb, so we only
         * need to set it on the dup_fc as this is what creates the super block.
         */
        dup_fc->s_fs_info = fs_info;

        /*
         * We'll do the security settings in our btrfs_get_tree_super() mount
         * loop, they were duplicated into dup_fc, we can drop the originals
         * here.
         */
        security_free_mnt_opts(&fc->security);
        fc->security = NULL;

        mnt = fc_mount(dup_fc);
        if (PTR_ERR_OR_ZERO(mnt) == -EBUSY)
                mnt = btrfs_reconfigure_for_mount(dup_fc);
        put_fs_context(dup_fc);
        if (IS_ERR(mnt))
                return PTR_ERR(mnt);

        /*
         * This free's ->subvol_name, because if it isn't set we have to
         * allocate a buffer to hold the subvol_name, so we just drop our
         * reference to it here.
         */
        dentry = mount_subvol(ctx->subvol_name, ctx->subvol_objectid, mnt);
        ctx->subvol_name = NULL;
        if (IS_ERR(dentry))
                return PTR_ERR(dentry);

        fc->root = dentry;
        return 0;
}

static int btrfs_get_tree(struct fs_context *fc)
{
        /*
         * Since we use mount_subtree to mount the default/specified subvol, we
         * have to do mounts in two steps.
         *
         * First pass through we call btrfs_get_tree_subvol(), this is just a
         * wrapper around fc_mount() to call back into here again, and this time
         * we'll call btrfs_get_tree_super().  This will do the open_ctree() and
         * everything to open the devices and file system.  Then we return back
         * with a fully constructed vfsmount in btrfs_get_tree_subvol(), and
         * from there we can do our mount_subvol() call, which will lookup
         * whichever subvol we're mounting and setup this fc with the
         * appropriate dentry for the subvol.
         */
        if (fc->s_fs_info)
                return btrfs_get_tree_super(fc);
        return btrfs_get_tree_subvol(fc);
}

static void btrfs_kill_super(struct super_block *sb)
{
        struct btrfs_fs_info *fs_info = btrfs_sb(sb);
        kill_anon_super(sb);
        btrfs_free_fs_info(fs_info);
}

static void btrfs_free_fs_context(struct fs_context *fc)
{
        struct btrfs_fs_context *ctx = fc->fs_private;
        struct btrfs_fs_info *fs_info = fc->s_fs_info;

        if (fs_info)
                btrfs_free_fs_info(fs_info);

        if (ctx && refcount_dec_and_test(&ctx->refs)) {
                kfree(ctx->subvol_name);
                kfree(ctx);
        }
}

static int btrfs_dup_fs_context(struct fs_context *fc, struct fs_context *src_fc)
{
        struct btrfs_fs_context *ctx = src_fc->fs_private;

        /*
         * Give a ref to our ctx to this dup, as we want to keep it around for
         * our original fc so we can have the subvolume name or objectid.
         *
         * We unset ->source in the original fc because the dup needs it for
         * mounting, and then once we free the dup it'll free ->source, so we
         * need to make sure we're only pointing to it in one fc.
         */
        refcount_inc(&ctx->refs);
        fc->fs_private = ctx;
        fc->source = src_fc->source;
        src_fc->source = NULL;
        return 0;
}

static const struct fs_context_operations btrfs_fs_context_ops = {
        .parse_param    = btrfs_parse_param,
        .reconfigure    = btrfs_reconfigure,
        .get_tree       = btrfs_get_tree,
        .dup            = btrfs_dup_fs_context,
        .free           = btrfs_free_fs_context,
};

static int btrfs_init_fs_context(struct fs_context *fc)
{
        struct btrfs_fs_context *ctx;

        ctx = kzalloc(sizeof(struct btrfs_fs_context), GFP_KERNEL);
        if (!ctx)
                return -ENOMEM;

        refcount_set(&ctx->refs, 1);
        fc->fs_private = ctx;
        fc->ops = &btrfs_fs_context_ops;

        if (fc->purpose == FS_CONTEXT_FOR_RECONFIGURE) {
                btrfs_info_to_ctx(btrfs_sb(fc->root->d_sb), ctx);
        } else {
                ctx->thread_pool_size =
                        min_t(unsigned long, num_online_cpus() + 2, 8);
                ctx->max_inline = BTRFS_DEFAULT_MAX_INLINE;
                ctx->commit_interval = BTRFS_DEFAULT_COMMIT_INTERVAL;
        }

#ifdef CONFIG_BTRFS_FS_POSIX_ACL
        fc->sb_flags |= SB_POSIXACL;
#endif
        fc->sb_flags |= SB_I_VERSION;

        return 0;
}

static struct file_system_type btrfs_fs_type = {
        .owner                  = THIS_MODULE,
        .name                   = "btrfs",
        .init_fs_context        = btrfs_init_fs_context,
        .parameters             = btrfs_fs_parameters,
        .kill_sb                = btrfs_kill_super,
        .fs_flags               = FS_REQUIRES_DEV | FS_BINARY_MOUNTDATA | FS_ALLOW_IDMAP,
 };

MODULE_ALIAS_FS("btrfs");

static int btrfs_control_open(struct inode *inode, struct file *file)
{
        /*
         * The control file's private_data is used to hold the
         * transaction when it is started and is used to keep
         * track of whether a transaction is already in progress.
         */
        file->private_data = NULL;
        return 0;
}

/*
 * Used by /dev/btrfs-control for devices ioctls.
 */
static long btrfs_control_ioctl(struct file *file, unsigned int cmd,
                                unsigned long arg)
{
        struct btrfs_ioctl_vol_args *vol;
        struct btrfs_device *device = NULL;
        dev_t devt = 0;
        int ret = -ENOTTY;

        if (!capable(CAP_SYS_ADMIN))
                return -EPERM;

        vol = memdup_user((void __user *)arg, sizeof(*vol));
        if (IS_ERR(vol))
                return PTR_ERR(vol);
        ret = btrfs_check_ioctl_vol_args_path(vol);
        if (ret < 0)
                goto out;

        switch (cmd) {
        case BTRFS_IOC_SCAN_DEV:
                mutex_lock(&uuid_mutex);
                /*
                 * Scanning outside of mount can return NULL which would turn
                 * into 0 error code.
                 */
                device = btrfs_scan_one_device(vol->name, BLK_OPEN_READ, false);
                ret = PTR_ERR_OR_ZERO(device);
                mutex_unlock(&uuid_mutex);
                break;
        case BTRFS_IOC_FORGET_DEV:
                if (vol->name[0] != 0) {
                        ret = lookup_bdev(vol->name, &devt);
                        if (ret)
                                break;
                }
                ret = btrfs_forget_devices(devt);
                break;
        case BTRFS_IOC_DEVICES_READY:
                mutex_lock(&uuid_mutex);
                /*
                 * Scanning outside of mount can return NULL which would turn
                 * into 0 error code.
                 */
                device = btrfs_scan_one_device(vol->name, BLK_OPEN_READ, false);
                if (IS_ERR_OR_NULL(device)) {
                        mutex_unlock(&uuid_mutex);
                        ret = PTR_ERR(device);
                        break;
                }
                ret = !(device->fs_devices->num_devices ==
                        device->fs_devices->total_devices);
                mutex_unlock(&uuid_mutex);
                break;
        case BTRFS_IOC_GET_SUPPORTED_FEATURES:
                ret = btrfs_ioctl_get_supported_features((void __user*)arg);
                break;
        }

out:
        kfree(vol);
        return ret;
}

static int btrfs_freeze(struct super_block *sb)
{
        struct btrfs_trans_handle *trans;
        struct btrfs_fs_info *fs_info = btrfs_sb(sb);
        struct btrfs_root *root = fs_info->tree_root;

        set_bit(BTRFS_FS_FROZEN, &fs_info->flags);
        /*
         * We don't need a barrier here, we'll wait for any transaction that
         * could be in progress on other threads (and do delayed iputs that
         * we want to avoid on a frozen filesystem), or do the commit
         * ourselves.
         */
        trans = btrfs_attach_transaction_barrier(root);
        if (IS_ERR(trans)) {
                /* no transaction, don't bother */
                if (PTR_ERR(trans) == -ENOENT)
                        return 0;
                return PTR_ERR(trans);
        }
        return btrfs_commit_transaction(trans);
}

static int check_dev_super(struct btrfs_device *dev)
{
        struct btrfs_fs_info *fs_info = dev->fs_info;
        struct btrfs_super_block *sb;
        u64 last_trans;
        u16 csum_type;
        int ret = 0;

        /* This should be called with fs still frozen. */
        ASSERT(test_bit(BTRFS_FS_FROZEN, &fs_info->flags));

        /* Missing dev, no need to check. */
        if (!dev->bdev)
                return 0;

        /* Only need to check the primary super block. */
        sb = btrfs_read_dev_one_super(dev->bdev, 0, true);
        if (IS_ERR(sb))
                return PTR_ERR(sb);

        /* Verify the checksum. */
        csum_type = btrfs_super_csum_type(sb);
        if (csum_type != btrfs_super_csum_type(fs_info->super_copy)) {
                btrfs_err(fs_info, "csum type changed, has %u expect %u",
                          csum_type, btrfs_super_csum_type(fs_info->super_copy));
                ret = -EUCLEAN;
                goto out;
        }

        if (btrfs_check_super_csum(fs_info, sb)) {
                btrfs_err(fs_info, "csum for on-disk super block no longer matches");
                ret = -EUCLEAN;
                goto out;
        }

        /* Btrfs_validate_super() includes fsid check against super->fsid. */
        ret = btrfs_validate_super(fs_info, sb, 0);
        if (ret < 0)
                goto out;

        last_trans = btrfs_get_last_trans_committed(fs_info);
        if (btrfs_super_generation(sb) != last_trans) {
                btrfs_err(fs_info, "transid mismatch, has %llu expect %llu",
                          btrfs_super_generation(sb), last_trans);
                ret = -EUCLEAN;
                goto out;
        }
out:
        btrfs_release_disk_super(sb);
        return ret;
}

static int btrfs_unfreeze(struct super_block *sb)
{
        struct btrfs_fs_info *fs_info = btrfs_sb(sb);
        struct btrfs_device *device;
        int ret = 0;

        /*
         * Make sure the fs is not changed by accident (like hibernation then
         * modified by other OS).
         * If we found anything wrong, we mark the fs error immediately.
         *
         * And since the fs is frozen, no one can modify the fs yet, thus
         * we don't need to hold device_list_mutex.
         */
        list_for_each_entry(device, &fs_info->fs_devices->devices, dev_list) {
                ret = check_dev_super(device);
                if (ret < 0) {
                        btrfs_handle_fs_error(fs_info, ret,
                                "super block on devid %llu got modified unexpectedly",
                                device->devid);
                        break;
                }
        }
        clear_bit(BTRFS_FS_FROZEN, &fs_info->flags);

        /*
         * We still return 0, to allow VFS layer to unfreeze the fs even the
         * above checks failed. Since the fs is either fine or read-only, we're
         * safe to continue, without causing further damage.
         */
        return 0;
}

static int btrfs_show_devname(struct seq_file *m, struct dentry *root)
{
        struct btrfs_fs_info *fs_info = btrfs_sb(root->d_sb);

        /*
         * There should be always a valid pointer in latest_dev, it may be stale
         * for a short moment in case it's being deleted but still valid until
         * the end of RCU grace period.
         */
        rcu_read_lock();
        seq_escape(m, btrfs_dev_name(fs_info->fs_devices->latest_dev), " \t\n\\");
        rcu_read_unlock();

        return 0;
}

static long btrfs_nr_cached_objects(struct super_block *sb, struct shrink_control *sc)
{
        struct btrfs_fs_info *fs_info = btrfs_sb(sb);
        const s64 nr = percpu_counter_sum_positive(&fs_info->evictable_extent_maps);

        trace_btrfs_extent_map_shrinker_count(fs_info, nr);

        return nr;
}

static long btrfs_free_cached_objects(struct super_block *sb, struct shrink_control *sc)
{
        const long nr_to_scan = min_t(unsigned long, LONG_MAX, sc->nr_to_scan);
        struct btrfs_fs_info *fs_info = btrfs_sb(sb);

        return btrfs_free_extent_maps(fs_info, nr_to_scan);
}

static const struct super_operations btrfs_super_ops = {
        .drop_inode     = btrfs_drop_inode,
        .evict_inode    = btrfs_evict_inode,
        .put_super      = btrfs_put_super,
        .sync_fs        = btrfs_sync_fs,
        .show_options   = btrfs_show_options,
        .show_devname   = btrfs_show_devname,
        .alloc_inode    = btrfs_alloc_inode,
        .destroy_inode  = btrfs_destroy_inode,
        .free_inode     = btrfs_free_inode,
        .statfs         = btrfs_statfs,
        .freeze_fs      = btrfs_freeze,
        .unfreeze_fs    = btrfs_unfreeze,
        .nr_cached_objects = btrfs_nr_cached_objects,
        .free_cached_objects = btrfs_free_cached_objects,
};

static const struct file_operations btrfs_ctl_fops = {
        .open = btrfs_control_open,
        .unlocked_ioctl  = btrfs_control_ioctl,
        .compat_ioctl = compat_ptr_ioctl,
        .owner   = THIS_MODULE,
        .llseek = noop_llseek,
};

static struct miscdevice btrfs_misc = {
        .minor          = BTRFS_MINOR,
        .name           = "btrfs-control",
        .fops           = &btrfs_ctl_fops
};

MODULE_ALIAS_MISCDEV(BTRFS_MINOR);
MODULE_ALIAS("devname:btrfs-control");

static int __init btrfs_interface_init(void)
{
        return misc_register(&btrfs_misc);
}

static __cold void btrfs_interface_exit(void)
{
        misc_deregister(&btrfs_misc);
}

static int __init btrfs_print_mod_info(void)
{
        static const char options[] = ""
#ifdef CONFIG_BTRFS_DEBUG
                        ", debug=on"
#endif
#ifdef CONFIG_BTRFS_ASSERT
                        ", assert=on"
#endif
#ifdef CONFIG_BTRFS_FS_REF_VERIFY
                        ", ref-verify=on"
#endif
#ifdef CONFIG_BLK_DEV_ZONED
                        ", zoned=yes"
#else
                        ", zoned=no"
#endif
#ifdef CONFIG_FS_VERITY
                        ", fsverity=yes"
#else
                        ", fsverity=no"
#endif
                        ;
        pr_info("Btrfs loaded%s\n", options);
        return 0;
}

static int register_btrfs(void)
{
        return register_filesystem(&btrfs_fs_type);
}

static void unregister_btrfs(void)
{
        unregister_filesystem(&btrfs_fs_type);
}

/* Helper structure for long init/exit functions. */
struct init_sequence {
        int (*init_func)(void);
        /* Can be NULL if the init_func doesn't need cleanup. */
        void (*exit_func)(void);
};

static const struct init_sequence mod_init_seq[] = {
        {
                .init_func = btrfs_props_init,
                .exit_func = NULL,
        }, {
                .init_func = btrfs_init_sysfs,
                .exit_func = btrfs_exit_sysfs,
        }, {
                .init_func = btrfs_init_compress,
                .exit_func = btrfs_exit_compress,
        }, {
                .init_func = btrfs_init_cachep,
                .exit_func = btrfs_destroy_cachep,
        }, {
                .init_func = btrfs_transaction_init,
                .exit_func = btrfs_transaction_exit,
        }, {
                .init_func = btrfs_ctree_init,
                .exit_func = btrfs_ctree_exit,
        }, {
                .init_func = btrfs_free_space_init,
                .exit_func = btrfs_free_space_exit,
        }, {
                .init_func = extent_state_init_cachep,
                .exit_func = extent_state_free_cachep,
        }, {
                .init_func = extent_buffer_init_cachep,
                .exit_func = extent_buffer_free_cachep,
        }, {
                .init_func = btrfs_bioset_init,
                .exit_func = btrfs_bioset_exit,
        }, {
                .init_func = extent_map_init,
                .exit_func = extent_map_exit,
        }, {
                .init_func = ordered_data_init,
                .exit_func = ordered_data_exit,
        }, {
                .init_func = btrfs_delayed_inode_init,
                .exit_func = btrfs_delayed_inode_exit,
        }, {
                .init_func = btrfs_auto_defrag_init,
                .exit_func = btrfs_auto_defrag_exit,
        }, {
                .init_func = btrfs_delayed_ref_init,
                .exit_func = btrfs_delayed_ref_exit,
        }, {
                .init_func = btrfs_prelim_ref_init,
                .exit_func = btrfs_prelim_ref_exit,
        }, {
                .init_func = btrfs_interface_init,
                .exit_func = btrfs_interface_exit,
        }, {
                .init_func = btrfs_print_mod_info,
                .exit_func = NULL,
        }, {
                .init_func = btrfs_run_sanity_tests,
                .exit_func = NULL,
        }, {
                .init_func = register_btrfs,
                .exit_func = unregister_btrfs,
        }
};

static bool mod_init_result[ARRAY_SIZE(mod_init_seq)];

static __always_inline void btrfs_exit_btrfs_fs(void)
{
        int i;

        for (i = ARRAY_SIZE(mod_init_seq) - 1; i >= 0; i--) {
                if (!mod_init_result[i])
                        continue;
                if (mod_init_seq[i].exit_func)
                        mod_init_seq[i].exit_func();
                mod_init_result[i] = false;
        }
}

static void __exit exit_btrfs_fs(void)
{
        btrfs_exit_btrfs_fs();
        btrfs_cleanup_fs_uuids();
}

static int __init init_btrfs_fs(void)
{
        int ret;
        int i;

        for (i = 0; i < ARRAY_SIZE(mod_init_seq); i++) {
                ASSERT(!mod_init_result[i]);
                ret = mod_init_seq[i].init_func();
                if (ret < 0) {
                        btrfs_exit_btrfs_fs();
                        return ret;
                }
                mod_init_result[i] = true;
        }
        return 0;
}

late_initcall(init_btrfs_fs);
module_exit(exit_btrfs_fs)

MODULE_LICENSE("GPL");
MODULE_SOFTDEP("pre: crc32c");
MODULE_SOFTDEP("pre: xxhash64");
MODULE_SOFTDEP("pre: sha256");
MODULE_SOFTDEP("pre: blake2b-256");