cifs: Fix SMB1 readv/writev callback in the same way as SMB2/3

[linux.git] / net / core / page_pool.c

/* SPDX-License-Identifier: GPL-2.0
 *
 * page_pool.c
 *      Author: Jesper Dangaard Brouer <[email protected]>
 *      Copyright (C) 2016 Red Hat, Inc.
 */

#include <linux/error-injection.h>
#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/slab.h>
#include <linux/device.h>

#include <net/page_pool/helpers.h>
#include <net/xdp.h>

#include <linux/dma-direction.h>
#include <linux/dma-mapping.h>
#include <linux/page-flags.h>
#include <linux/mm.h> /* for put_page() */
#include <linux/poison.h>
#include <linux/ethtool.h>
#include <linux/netdevice.h>

#include <trace/events/page_pool.h>

#include "page_pool_priv.h"

#define DEFER_TIME (msecs_to_jiffies(1000))
#define DEFER_WARN_INTERVAL (60 * HZ)

#define BIAS_MAX        (LONG_MAX >> 1)

#ifdef CONFIG_PAGE_POOL_STATS
static DEFINE_PER_CPU(struct page_pool_recycle_stats, pp_system_recycle_stats);

/* alloc_stat_inc is intended to be used in softirq context */
#define alloc_stat_inc(pool, __stat)    (pool->alloc_stats.__stat++)
/* recycle_stat_inc is safe to use when preemption is possible. */
#define recycle_stat_inc(pool, __stat)                                                  \
        do {                                                                            \
                struct page_pool_recycle_stats __percpu *s = pool->recycle_stats;       \
                this_cpu_inc(s->__stat);                                                \
        } while (0)

#define recycle_stat_add(pool, __stat, val)                                             \
        do {                                                                            \
                struct page_pool_recycle_stats __percpu *s = pool->recycle_stats;       \
                this_cpu_add(s->__stat, val);                                           \
        } while (0)

static const char pp_stats[][ETH_GSTRING_LEN] = {
        "rx_pp_alloc_fast",
        "rx_pp_alloc_slow",
        "rx_pp_alloc_slow_ho",
        "rx_pp_alloc_empty",
        "rx_pp_alloc_refill",
        "rx_pp_alloc_waive",
        "rx_pp_recycle_cached",
        "rx_pp_recycle_cache_full",
        "rx_pp_recycle_ring",
        "rx_pp_recycle_ring_full",
        "rx_pp_recycle_released_ref",
};

/**
 * page_pool_get_stats() - fetch page pool stats
 * @pool:       pool from which page was allocated
 * @stats:      struct page_pool_stats to fill in
 *
 * Retrieve statistics about the page_pool. This API is only available
 * if the kernel has been configured with ``CONFIG_PAGE_POOL_STATS=y``.
 * A pointer to a caller allocated struct page_pool_stats structure
 * is passed to this API which is filled in. The caller can then report
 * those stats to the user (perhaps via ethtool, debugfs, etc.).
 */
bool page_pool_get_stats(const struct page_pool *pool,
                         struct page_pool_stats *stats)
{
        int cpu = 0;

        if (!stats)
                return false;

        /* The caller is responsible to initialize stats. */
        stats->alloc_stats.fast += pool->alloc_stats.fast;
        stats->alloc_stats.slow += pool->alloc_stats.slow;
        stats->alloc_stats.slow_high_order += pool->alloc_stats.slow_high_order;
        stats->alloc_stats.empty += pool->alloc_stats.empty;
        stats->alloc_stats.refill += pool->alloc_stats.refill;
        stats->alloc_stats.waive += pool->alloc_stats.waive;

        for_each_possible_cpu(cpu) {
                const struct page_pool_recycle_stats *pcpu =
                        per_cpu_ptr(pool->recycle_stats, cpu);

                stats->recycle_stats.cached += pcpu->cached;
                stats->recycle_stats.cache_full += pcpu->cache_full;
                stats->recycle_stats.ring += pcpu->ring;
                stats->recycle_stats.ring_full += pcpu->ring_full;
                stats->recycle_stats.released_refcnt += pcpu->released_refcnt;
        }

        return true;
}
EXPORT_SYMBOL(page_pool_get_stats);

u8 *page_pool_ethtool_stats_get_strings(u8 *data)
{
        int i;

        for (i = 0; i < ARRAY_SIZE(pp_stats); i++) {
                memcpy(data, pp_stats[i], ETH_GSTRING_LEN);
                data += ETH_GSTRING_LEN;
        }

        return data;
}
EXPORT_SYMBOL(page_pool_ethtool_stats_get_strings);

int page_pool_ethtool_stats_get_count(void)
{
        return ARRAY_SIZE(pp_stats);
}
EXPORT_SYMBOL(page_pool_ethtool_stats_get_count);

u64 *page_pool_ethtool_stats_get(u64 *data, const void *stats)
{
        const struct page_pool_stats *pool_stats = stats;

        *data++ = pool_stats->alloc_stats.fast;
        *data++ = pool_stats->alloc_stats.slow;
        *data++ = pool_stats->alloc_stats.slow_high_order;
        *data++ = pool_stats->alloc_stats.empty;
        *data++ = pool_stats->alloc_stats.refill;
        *data++ = pool_stats->alloc_stats.waive;
        *data++ = pool_stats->recycle_stats.cached;
        *data++ = pool_stats->recycle_stats.cache_full;
        *data++ = pool_stats->recycle_stats.ring;
        *data++ = pool_stats->recycle_stats.ring_full;
        *data++ = pool_stats->recycle_stats.released_refcnt;

        return data;
}
EXPORT_SYMBOL(page_pool_ethtool_stats_get);

#else
#define alloc_stat_inc(pool, __stat)
#define recycle_stat_inc(pool, __stat)
#define recycle_stat_add(pool, __stat, val)
#endif

static bool page_pool_producer_lock(struct page_pool *pool)
        __acquires(&pool->ring.producer_lock)
{
        bool in_softirq = in_softirq();

        if (in_softirq)
                spin_lock(&pool->ring.producer_lock);
        else
                spin_lock_bh(&pool->ring.producer_lock);

        return in_softirq;
}

static void page_pool_producer_unlock(struct page_pool *pool,
                                      bool in_softirq)
        __releases(&pool->ring.producer_lock)
{
        if (in_softirq)
                spin_unlock(&pool->ring.producer_lock);
        else
                spin_unlock_bh(&pool->ring.producer_lock);
}

static void page_pool_struct_check(void)
{
        CACHELINE_ASSERT_GROUP_MEMBER(struct page_pool, frag, frag_users);
        CACHELINE_ASSERT_GROUP_MEMBER(struct page_pool, frag, frag_page);
        CACHELINE_ASSERT_GROUP_MEMBER(struct page_pool, frag, frag_offset);
        CACHELINE_ASSERT_GROUP_SIZE(struct page_pool, frag,
                                    PAGE_POOL_FRAG_GROUP_ALIGN);
}

static int page_pool_init(struct page_pool *pool,
                          const struct page_pool_params *params,
                          int cpuid)
{
        unsigned int ring_qsize = 1024; /* Default */

        page_pool_struct_check();

        memcpy(&pool->p, &params->fast, sizeof(pool->p));
        memcpy(&pool->slow, &params->slow, sizeof(pool->slow));

        pool->cpuid = cpuid;

        /* Validate only known flags were used */
        if (pool->slow.flags & ~PP_FLAG_ALL)
                return -EINVAL;

        if (pool->p.pool_size)
                ring_qsize = pool->p.pool_size;

        /* Sanity limit mem that can be pinned down */
        if (ring_qsize > 32768)
                return -E2BIG;

        /* DMA direction is either DMA_FROM_DEVICE or DMA_BIDIRECTIONAL.
         * DMA_BIDIRECTIONAL is for allowing page used for DMA sending,
         * which is the XDP_TX use-case.
         */
        if (pool->slow.flags & PP_FLAG_DMA_MAP) {
                if ((pool->p.dma_dir != DMA_FROM_DEVICE) &&
                    (pool->p.dma_dir != DMA_BIDIRECTIONAL))
                        return -EINVAL;

                pool->dma_map = true;
        }

        if (pool->slow.flags & PP_FLAG_DMA_SYNC_DEV) {
                /* In order to request DMA-sync-for-device the page
                 * needs to be mapped
                 */
                if (!(pool->slow.flags & PP_FLAG_DMA_MAP))
                        return -EINVAL;

                if (!pool->p.max_len)
                        return -EINVAL;

                pool->dma_sync = true;

                /* pool->p.offset has to be set according to the address
                 * offset used by the DMA engine to start copying rx data
                 */
        }

        pool->has_init_callback = !!pool->slow.init_callback;

#ifdef CONFIG_PAGE_POOL_STATS
        if (!(pool->slow.flags & PP_FLAG_SYSTEM_POOL)) {
                pool->recycle_stats = alloc_percpu(struct page_pool_recycle_stats);
                if (!pool->recycle_stats)
                        return -ENOMEM;
        } else {
                /* For system page pool instance we use a singular stats object
                 * instead of allocating a separate percpu variable for each
                 * (also percpu) page pool instance.
                 */
                pool->recycle_stats = &pp_system_recycle_stats;
                pool->system = true;
        }
#endif

        if (ptr_ring_init(&pool->ring, ring_qsize, GFP_KERNEL) < 0) {
#ifdef CONFIG_PAGE_POOL_STATS
                if (!pool->system)
                        free_percpu(pool->recycle_stats);
#endif
                return -ENOMEM;
        }

        atomic_set(&pool->pages_state_release_cnt, 0);

        /* Driver calling page_pool_create() also call page_pool_destroy() */
        refcount_set(&pool->user_cnt, 1);

        if (pool->dma_map)
                get_device(pool->p.dev);

        return 0;
}

static void page_pool_uninit(struct page_pool *pool)
{
        ptr_ring_cleanup(&pool->ring, NULL);

        if (pool->dma_map)
                put_device(pool->p.dev);

#ifdef CONFIG_PAGE_POOL_STATS
        if (!pool->system)
                free_percpu(pool->recycle_stats);
#endif
}

/**
 * page_pool_create_percpu() - create a page pool for a given cpu.
 * @params: parameters, see struct page_pool_params
 * @cpuid: cpu identifier
 */
struct page_pool *
page_pool_create_percpu(const struct page_pool_params *params, int cpuid)
{
        struct page_pool *pool;
        int err;

        pool = kzalloc_node(sizeof(*pool), GFP_KERNEL, params->nid);
        if (!pool)
                return ERR_PTR(-ENOMEM);

        err = page_pool_init(pool, params, cpuid);
        if (err < 0)
                goto err_free;

        err = page_pool_list(pool);
        if (err)
                goto err_uninit;

        return pool;

err_uninit:
        page_pool_uninit(pool);
err_free:
        pr_warn("%s() gave up with errno %d\n", __func__, err);
        kfree(pool);
        return ERR_PTR(err);
}
EXPORT_SYMBOL(page_pool_create_percpu);

/**
 * page_pool_create() - create a page pool
 * @params: parameters, see struct page_pool_params
 */
struct page_pool *page_pool_create(const struct page_pool_params *params)
{
        return page_pool_create_percpu(params, -1);
}
EXPORT_SYMBOL(page_pool_create);

static void page_pool_return_page(struct page_pool *pool, netmem_ref netmem);

static noinline netmem_ref page_pool_refill_alloc_cache(struct page_pool *pool)
{
        struct ptr_ring *r = &pool->ring;
        netmem_ref netmem;
        int pref_nid; /* preferred NUMA node */

        /* Quicker fallback, avoid locks when ring is empty */
        if (__ptr_ring_empty(r)) {
                alloc_stat_inc(pool, empty);
                return 0;
        }

        /* Softirq guarantee CPU and thus NUMA node is stable. This,
         * assumes CPU refilling driver RX-ring will also run RX-NAPI.
         */
#ifdef CONFIG_NUMA
        pref_nid = (pool->p.nid == NUMA_NO_NODE) ? numa_mem_id() : pool->p.nid;
#else
        /* Ignore pool->p.nid setting if !CONFIG_NUMA, helps compiler */
        pref_nid = numa_mem_id(); /* will be zero like page_to_nid() */
#endif

        /* Refill alloc array, but only if NUMA match */
        do {
                netmem = (__force netmem_ref)__ptr_ring_consume(r);
                if (unlikely(!netmem))
                        break;

                if (likely(page_to_nid(netmem_to_page(netmem)) == pref_nid)) {
                        pool->alloc.cache[pool->alloc.count++] = netmem;
                } else {
                        /* NUMA mismatch;
                         * (1) release 1 page to page-allocator and
                         * (2) break out to fallthrough to alloc_pages_node.
                         * This limit stress on page buddy alloactor.
                         */
                        page_pool_return_page(pool, netmem);
                        alloc_stat_inc(pool, waive);
                        netmem = 0;
                        break;
                }
        } while (pool->alloc.count < PP_ALLOC_CACHE_REFILL);

        /* Return last page */
        if (likely(pool->alloc.count > 0)) {
                netmem = pool->alloc.cache[--pool->alloc.count];
                alloc_stat_inc(pool, refill);
        }

        return netmem;
}

/* fast path */
static netmem_ref __page_pool_get_cached(struct page_pool *pool)
{
        netmem_ref netmem;

        /* Caller MUST guarantee safe non-concurrent access, e.g. softirq */
        if (likely(pool->alloc.count)) {
                /* Fast-path */
                netmem = pool->alloc.cache[--pool->alloc.count];
                alloc_stat_inc(pool, fast);
        } else {
                netmem = page_pool_refill_alloc_cache(pool);
        }

        return netmem;
}

static void __page_pool_dma_sync_for_device(const struct page_pool *pool,
                                            netmem_ref netmem,
                                            u32 dma_sync_size)
{
#if defined(CONFIG_HAS_DMA) && defined(CONFIG_DMA_NEED_SYNC)
        dma_addr_t dma_addr = page_pool_get_dma_addr_netmem(netmem);

        dma_sync_size = min(dma_sync_size, pool->p.max_len);
        __dma_sync_single_for_device(pool->p.dev, dma_addr + pool->p.offset,
                                     dma_sync_size, pool->p.dma_dir);
#endif
}

static __always_inline void
page_pool_dma_sync_for_device(const struct page_pool *pool,
                              netmem_ref netmem,
                              u32 dma_sync_size)
{
        if (pool->dma_sync && dma_dev_need_sync(pool->p.dev))
                __page_pool_dma_sync_for_device(pool, netmem, dma_sync_size);
}

static bool page_pool_dma_map(struct page_pool *pool, netmem_ref netmem)
{
        dma_addr_t dma;

        /* Setup DMA mapping: use 'struct page' area for storing DMA-addr
         * since dma_addr_t can be either 32 or 64 bits and does not always fit
         * into page private data (i.e 32bit cpu with 64bit DMA caps)
         * This mapping is kept for lifetime of page, until leaving pool.
         */
        dma = dma_map_page_attrs(pool->p.dev, netmem_to_page(netmem), 0,
                                 (PAGE_SIZE << pool->p.order), pool->p.dma_dir,
                                 DMA_ATTR_SKIP_CPU_SYNC |
                                         DMA_ATTR_WEAK_ORDERING);
        if (dma_mapping_error(pool->p.dev, dma))
                return false;

        if (page_pool_set_dma_addr_netmem(netmem, dma))
                goto unmap_failed;

        page_pool_dma_sync_for_device(pool, netmem, pool->p.max_len);

        return true;

unmap_failed:
        WARN_ONCE(1, "unexpected DMA address, please report to netdev@");
        dma_unmap_page_attrs(pool->p.dev, dma,
                             PAGE_SIZE << pool->p.order, pool->p.dma_dir,
                             DMA_ATTR_SKIP_CPU_SYNC | DMA_ATTR_WEAK_ORDERING);
        return false;
}

static void page_pool_set_pp_info(struct page_pool *pool, netmem_ref netmem)
{
        struct page *page = netmem_to_page(netmem);

        page->pp = pool;
        page->pp_magic |= PP_SIGNATURE;

        /* Ensuring all pages have been split into one fragment initially:
         * page_pool_set_pp_info() is only called once for every page when it
         * is allocated from the page allocator and page_pool_fragment_page()
         * is dirtying the same cache line as the page->pp_magic above, so
         * the overhead is negligible.
         */
        page_pool_fragment_netmem(netmem, 1);
        if (pool->has_init_callback)
                pool->slow.init_callback(netmem, pool->slow.init_arg);
}

static void page_pool_clear_pp_info(netmem_ref netmem)
{
        struct page *page = netmem_to_page(netmem);

        page->pp_magic = 0;
        page->pp = NULL;
}

static struct page *__page_pool_alloc_page_order(struct page_pool *pool,
                                                 gfp_t gfp)
{
        struct page *page;

        gfp |= __GFP_COMP;
        page = alloc_pages_node(pool->p.nid, gfp, pool->p.order);
        if (unlikely(!page))
                return NULL;

        if (pool->dma_map && unlikely(!page_pool_dma_map(pool, page_to_netmem(page)))) {
                put_page(page);
                return NULL;
        }

        alloc_stat_inc(pool, slow_high_order);
        page_pool_set_pp_info(pool, page_to_netmem(page));

        /* Track how many pages are held 'in-flight' */
        pool->pages_state_hold_cnt++;
        trace_page_pool_state_hold(pool, page_to_netmem(page),
                                   pool->pages_state_hold_cnt);
        return page;
}

/* slow path */
static noinline netmem_ref __page_pool_alloc_pages_slow(struct page_pool *pool,
                                                        gfp_t gfp)
{
        const int bulk = PP_ALLOC_CACHE_REFILL;
        unsigned int pp_order = pool->p.order;
        bool dma_map = pool->dma_map;
        netmem_ref netmem;
        int i, nr_pages;

        /* Don't support bulk alloc for high-order pages */
        if (unlikely(pp_order))
                return page_to_netmem(__page_pool_alloc_page_order(pool, gfp));

        /* Unnecessary as alloc cache is empty, but guarantees zero count */
        if (unlikely(pool->alloc.count > 0))
                return pool->alloc.cache[--pool->alloc.count];

        /* Mark empty alloc.cache slots "empty" for alloc_pages_bulk_array */
        memset(&pool->alloc.cache, 0, sizeof(void *) * bulk);

        nr_pages = alloc_pages_bulk_array_node(gfp,
                                               pool->p.nid, bulk,
                                               (struct page **)pool->alloc.cache);
        if (unlikely(!nr_pages))
                return 0;

        /* Pages have been filled into alloc.cache array, but count is zero and
         * page element have not been (possibly) DMA mapped.
         */
        for (i = 0; i < nr_pages; i++) {
                netmem = pool->alloc.cache[i];
                if (dma_map && unlikely(!page_pool_dma_map(pool, netmem))) {
                        put_page(netmem_to_page(netmem));
                        continue;
                }

                page_pool_set_pp_info(pool, netmem);
                pool->alloc.cache[pool->alloc.count++] = netmem;
                /* Track how many pages are held 'in-flight' */
                pool->pages_state_hold_cnt++;
                trace_page_pool_state_hold(pool, netmem,
                                           pool->pages_state_hold_cnt);
        }

        /* Return last page */
        if (likely(pool->alloc.count > 0)) {
                netmem = pool->alloc.cache[--pool->alloc.count];
                alloc_stat_inc(pool, slow);
        } else {
                netmem = 0;
        }

        /* When page just alloc'ed is should/must have refcnt 1. */
        return netmem;
}

/* For using page_pool replace: alloc_pages() API calls, but provide
 * synchronization guarantee for allocation side.
 */
netmem_ref page_pool_alloc_netmem(struct page_pool *pool, gfp_t gfp)
{
        netmem_ref netmem;

        /* Fast-path: Get a page from cache */
        netmem = __page_pool_get_cached(pool);
        if (netmem)
                return netmem;

        /* Slow-path: cache empty, do real allocation */
        netmem = __page_pool_alloc_pages_slow(pool, gfp);
        return netmem;
}
EXPORT_SYMBOL(page_pool_alloc_netmem);

struct page *page_pool_alloc_pages(struct page_pool *pool, gfp_t gfp)
{
        return netmem_to_page(page_pool_alloc_netmem(pool, gfp));
}
EXPORT_SYMBOL(page_pool_alloc_pages);
ALLOW_ERROR_INJECTION(page_pool_alloc_pages, NULL);

/* Calculate distance between two u32 values, valid if distance is below 2^(31)
 *  https://en.wikipedia.org/wiki/Serial_number_arithmetic#General_Solution
 */
#define _distance(a, b) (s32)((a) - (b))

s32 page_pool_inflight(const struct page_pool *pool, bool strict)
{
        u32 release_cnt = atomic_read(&pool->pages_state_release_cnt);
        u32 hold_cnt = READ_ONCE(pool->pages_state_hold_cnt);
        s32 inflight;

        inflight = _distance(hold_cnt, release_cnt);

        if (strict) {
                trace_page_pool_release(pool, inflight, hold_cnt, release_cnt);
                WARN(inflight < 0, "Negative(%d) inflight packet-pages",
                     inflight);
        } else {
                inflight = max(0, inflight);
        }

        return inflight;
}

static __always_inline void __page_pool_release_page_dma(struct page_pool *pool,
                                                         netmem_ref netmem)
{
        dma_addr_t dma;

        if (!pool->dma_map)
                /* Always account for inflight pages, even if we didn't
                 * map them
                 */
                return;

        dma = page_pool_get_dma_addr_netmem(netmem);

        /* When page is unmapped, it cannot be returned to our pool */
        dma_unmap_page_attrs(pool->p.dev, dma,
                             PAGE_SIZE << pool->p.order, pool->p.dma_dir,
                             DMA_ATTR_SKIP_CPU_SYNC | DMA_ATTR_WEAK_ORDERING);
        page_pool_set_dma_addr_netmem(netmem, 0);
}

/* Disconnects a page (from a page_pool).  API users can have a need
 * to disconnect a page (from a page_pool), to allow it to be used as
 * a regular page (that will eventually be returned to the normal
 * page-allocator via put_page).
 */
void page_pool_return_page(struct page_pool *pool, netmem_ref netmem)
{
        int count;

        __page_pool_release_page_dma(pool, netmem);

        /* This may be the last page returned, releasing the pool, so
         * it is not safe to reference pool afterwards.
         */
        count = atomic_inc_return_relaxed(&pool->pages_state_release_cnt);
        trace_page_pool_state_release(pool, netmem, count);

        page_pool_clear_pp_info(netmem);
        put_page(netmem_to_page(netmem));
        /* An optimization would be to call __free_pages(page, pool->p.order)
         * knowing page is not part of page-cache (thus avoiding a
         * __page_cache_release() call).
         */
}

static bool page_pool_recycle_in_ring(struct page_pool *pool, netmem_ref netmem)
{
        int ret;
        /* BH protection not needed if current is softirq */
        if (in_softirq())
                ret = ptr_ring_produce(&pool->ring, (__force void *)netmem);
        else
                ret = ptr_ring_produce_bh(&pool->ring, (__force void *)netmem);

        if (!ret) {
                recycle_stat_inc(pool, ring);
                return true;
        }

        return false;
}

/* Only allow direct recycling in special circumstances, into the
 * alloc side cache.  E.g. during RX-NAPI processing for XDP_DROP use-case.
 *
 * Caller must provide appropriate safe context.
 */
static bool page_pool_recycle_in_cache(netmem_ref netmem,
                                       struct page_pool *pool)
{
        if (unlikely(pool->alloc.count == PP_ALLOC_CACHE_SIZE)) {
                recycle_stat_inc(pool, cache_full);
                return false;
        }

        /* Caller MUST have verified/know (page_ref_count(page) == 1) */
        pool->alloc.cache[pool->alloc.count++] = netmem;
        recycle_stat_inc(pool, cached);
        return true;
}

static bool __page_pool_page_can_be_recycled(netmem_ref netmem)
{
        return page_ref_count(netmem_to_page(netmem)) == 1 &&
               !page_is_pfmemalloc(netmem_to_page(netmem));
}

/* If the page refcnt == 1, this will try to recycle the page.
 * If pool->dma_sync is set, we'll try to sync the DMA area for
 * the configured size min(dma_sync_size, pool->max_len).
 * If the page refcnt != 1, then the page will be returned to memory
 * subsystem.
 */
static __always_inline netmem_ref
__page_pool_put_page(struct page_pool *pool, netmem_ref netmem,
                     unsigned int dma_sync_size, bool allow_direct)
{
        lockdep_assert_no_hardirq();

        /* This allocator is optimized for the XDP mode that uses
         * one-frame-per-page, but have fallbacks that act like the
         * regular page allocator APIs.
         *
         * refcnt == 1 means page_pool owns page, and can recycle it.
         *
         * page is NOT reusable when allocated when system is under
         * some pressure. (page_is_pfmemalloc)
         */
        if (likely(__page_pool_page_can_be_recycled(netmem))) {
                /* Read barrier done in page_ref_count / READ_ONCE */

                page_pool_dma_sync_for_device(pool, netmem, dma_sync_size);

                if (allow_direct && page_pool_recycle_in_cache(netmem, pool))
                        return 0;

                /* Page found as candidate for recycling */
                return netmem;
        }
        /* Fallback/non-XDP mode: API user have elevated refcnt.
         *
         * Many drivers split up the page into fragments, and some
         * want to keep doing this to save memory and do refcnt based
         * recycling. Support this use case too, to ease drivers
         * switching between XDP/non-XDP.
         *
         * In-case page_pool maintains the DMA mapping, API user must
         * call page_pool_put_page once.  In this elevated refcnt
         * case, the DMA is unmapped/released, as driver is likely
         * doing refcnt based recycle tricks, meaning another process
         * will be invoking put_page.
         */
        recycle_stat_inc(pool, released_refcnt);
        page_pool_return_page(pool, netmem);

        return 0;
}

static bool page_pool_napi_local(const struct page_pool *pool)
{
        const struct napi_struct *napi;
        u32 cpuid;

        if (unlikely(!in_softirq()))
                return false;

        /* Allow direct recycle if we have reasons to believe that we are
         * in the same context as the consumer would run, so there's
         * no possible race.
         * __page_pool_put_page() makes sure we're not in hardirq context
         * and interrupts are enabled prior to accessing the cache.
         */
        cpuid = smp_processor_id();
        if (READ_ONCE(pool->cpuid) == cpuid)
                return true;

        napi = READ_ONCE(pool->p.napi);

        return napi && READ_ONCE(napi->list_owner) == cpuid;
}

void page_pool_put_unrefed_netmem(struct page_pool *pool, netmem_ref netmem,
                                  unsigned int dma_sync_size, bool allow_direct)
{
        if (!allow_direct)
                allow_direct = page_pool_napi_local(pool);

        netmem =
                __page_pool_put_page(pool, netmem, dma_sync_size, allow_direct);
        if (netmem && !page_pool_recycle_in_ring(pool, netmem)) {
                /* Cache full, fallback to free pages */
                recycle_stat_inc(pool, ring_full);
                page_pool_return_page(pool, netmem);
        }
}
EXPORT_SYMBOL(page_pool_put_unrefed_netmem);

void page_pool_put_unrefed_page(struct page_pool *pool, struct page *page,
                                unsigned int dma_sync_size, bool allow_direct)
{
        page_pool_put_unrefed_netmem(pool, page_to_netmem(page), dma_sync_size,
                                     allow_direct);
}
EXPORT_SYMBOL(page_pool_put_unrefed_page);

/**
 * page_pool_put_page_bulk() - release references on multiple pages
 * @pool:       pool from which pages were allocated
 * @data:       array holding page pointers
 * @count:      number of pages in @data
 *
 * Tries to refill a number of pages into the ptr_ring cache holding ptr_ring
 * producer lock. If the ptr_ring is full, page_pool_put_page_bulk()
 * will release leftover pages to the page allocator.
 * page_pool_put_page_bulk() is suitable to be run inside the driver NAPI tx
 * completion loop for the XDP_REDIRECT use case.
 *
 * Please note the caller must not use data area after running
 * page_pool_put_page_bulk(), as this function overwrites it.
 */
void page_pool_put_page_bulk(struct page_pool *pool, void **data,
                             int count)
{
        int i, bulk_len = 0;
        bool allow_direct;
        bool in_softirq;

        allow_direct = page_pool_napi_local(pool);

        for (i = 0; i < count; i++) {
                netmem_ref netmem = page_to_netmem(virt_to_head_page(data[i]));

                /* It is not the last user for the page frag case */
                if (!page_pool_is_last_ref(netmem))
                        continue;

                netmem = __page_pool_put_page(pool, netmem, -1, allow_direct);
                /* Approved for bulk recycling in ptr_ring cache */
                if (netmem)
                        data[bulk_len++] = (__force void *)netmem;
        }

        if (!bulk_len)
                return;

        /* Bulk producer into ptr_ring page_pool cache */
        in_softirq = page_pool_producer_lock(pool);
        for (i = 0; i < bulk_len; i++) {
                if (__ptr_ring_produce(&pool->ring, data[i])) {
                        /* ring full */
                        recycle_stat_inc(pool, ring_full);
                        break;
                }
        }
        recycle_stat_add(pool, ring, i);
        page_pool_producer_unlock(pool, in_softirq);

        /* Hopefully all pages was return into ptr_ring */
        if (likely(i == bulk_len))
                return;

        /* ptr_ring cache full, free remaining pages outside producer lock
         * since put_page() with refcnt == 1 can be an expensive operation
         */
        for (; i < bulk_len; i++)
                page_pool_return_page(pool, (__force netmem_ref)data[i]);
}
EXPORT_SYMBOL(page_pool_put_page_bulk);

static netmem_ref page_pool_drain_frag(struct page_pool *pool,
                                       netmem_ref netmem)
{
        long drain_count = BIAS_MAX - pool->frag_users;

        /* Some user is still using the page frag */
        if (likely(page_pool_unref_netmem(netmem, drain_count)))
                return 0;

        if (__page_pool_page_can_be_recycled(netmem)) {
                page_pool_dma_sync_for_device(pool, netmem, -1);
                return netmem;
        }

        page_pool_return_page(pool, netmem);
        return 0;
}

static void page_pool_free_frag(struct page_pool *pool)
{
        long drain_count = BIAS_MAX - pool->frag_users;
        netmem_ref netmem = pool->frag_page;

        pool->frag_page = 0;

        if (!netmem || page_pool_unref_netmem(netmem, drain_count))
                return;

        page_pool_return_page(pool, netmem);
}

netmem_ref page_pool_alloc_frag_netmem(struct page_pool *pool,
                                       unsigned int *offset, unsigned int size,
                                       gfp_t gfp)
{
        unsigned int max_size = PAGE_SIZE << pool->p.order;
        netmem_ref netmem = pool->frag_page;

        if (WARN_ON(size > max_size))
                return 0;

        size = ALIGN(size, dma_get_cache_alignment());
        *offset = pool->frag_offset;

        if (netmem && *offset + size > max_size) {
                netmem = page_pool_drain_frag(pool, netmem);
                if (netmem) {
                        alloc_stat_inc(pool, fast);
                        goto frag_reset;
                }
        }

        if (!netmem) {
                netmem = page_pool_alloc_netmem(pool, gfp);
                if (unlikely(!netmem)) {
                        pool->frag_page = 0;
                        return 0;
                }

                pool->frag_page = netmem;

frag_reset:
                pool->frag_users = 1;
                *offset = 0;
                pool->frag_offset = size;
                page_pool_fragment_netmem(netmem, BIAS_MAX);
                return netmem;
        }

        pool->frag_users++;
        pool->frag_offset = *offset + size;
        alloc_stat_inc(pool, fast);
        return netmem;
}
EXPORT_SYMBOL(page_pool_alloc_frag_netmem);

struct page *page_pool_alloc_frag(struct page_pool *pool, unsigned int *offset,
                                  unsigned int size, gfp_t gfp)
{
        return netmem_to_page(page_pool_alloc_frag_netmem(pool, offset, size,
                                                          gfp));
}
EXPORT_SYMBOL(page_pool_alloc_frag);

static void page_pool_empty_ring(struct page_pool *pool)
{
        netmem_ref netmem;

        /* Empty recycle ring */
        while ((netmem = (__force netmem_ref)ptr_ring_consume_bh(&pool->ring))) {
                /* Verify the refcnt invariant of cached pages */
                if (!(page_ref_count(netmem_to_page(netmem)) == 1))
                        pr_crit("%s() page_pool refcnt %d violation\n",
                                __func__, netmem_ref_count(netmem));

                page_pool_return_page(pool, netmem);
        }
}

static void __page_pool_destroy(struct page_pool *pool)
{
        if (pool->disconnect)
                pool->disconnect(pool);

        page_pool_unlist(pool);
        page_pool_uninit(pool);
        kfree(pool);
}

static void page_pool_empty_alloc_cache_once(struct page_pool *pool)
{
        netmem_ref netmem;

        if (pool->destroy_cnt)
                return;

        /* Empty alloc cache, assume caller made sure this is
         * no-longer in use, and page_pool_alloc_pages() cannot be
         * call concurrently.
         */
        while (pool->alloc.count) {
                netmem = pool->alloc.cache[--pool->alloc.count];
                page_pool_return_page(pool, netmem);
        }
}

static void page_pool_scrub(struct page_pool *pool)
{
        page_pool_empty_alloc_cache_once(pool);
        pool->destroy_cnt++;

        /* No more consumers should exist, but producers could still
         * be in-flight.
         */
        page_pool_empty_ring(pool);
}

static int page_pool_release(struct page_pool *pool)
{
        int inflight;

        page_pool_scrub(pool);
        inflight = page_pool_inflight(pool, true);
        if (!inflight)
                __page_pool_destroy(pool);

        return inflight;
}

static void page_pool_release_retry(struct work_struct *wq)
{
        struct delayed_work *dwq = to_delayed_work(wq);
        struct page_pool *pool = container_of(dwq, typeof(*pool), release_dw);
        void *netdev;
        int inflight;

        inflight = page_pool_release(pool);
        if (!inflight)
                return;

        /* Periodic warning for page pools the user can't see */
        netdev = READ_ONCE(pool->slow.netdev);
        if (time_after_eq(jiffies, pool->defer_warn) &&
            (!netdev || netdev == NET_PTR_POISON)) {
                int sec = (s32)((u32)jiffies - (u32)pool->defer_start) / HZ;

                pr_warn("%s() stalled pool shutdown: id %u, %d inflight %d sec\n",
                        __func__, pool->user.id, inflight, sec);
                pool->defer_warn = jiffies + DEFER_WARN_INTERVAL;
        }

        /* Still not ready to be disconnected, retry later */
        schedule_delayed_work(&pool->release_dw, DEFER_TIME);
}

void page_pool_use_xdp_mem(struct page_pool *pool, void (*disconnect)(void *),
                           const struct xdp_mem_info *mem)
{
        refcount_inc(&pool->user_cnt);
        pool->disconnect = disconnect;
        pool->xdp_mem_id = mem->id;
}

void page_pool_disable_direct_recycling(struct page_pool *pool)
{
        /* Disable direct recycling based on pool->cpuid.
         * Paired with READ_ONCE() in page_pool_napi_local().
         */
        WRITE_ONCE(pool->cpuid, -1);

        if (!pool->p.napi)
                return;

        /* To avoid races with recycling and additional barriers make sure
         * pool and NAPI are unlinked when NAPI is disabled.
         */
        WARN_ON(!test_bit(NAPI_STATE_SCHED, &pool->p.napi->state));
        WARN_ON(READ_ONCE(pool->p.napi->list_owner) != -1);

        WRITE_ONCE(pool->p.napi, NULL);
}
EXPORT_SYMBOL(page_pool_disable_direct_recycling);

void page_pool_destroy(struct page_pool *pool)
{
        if (!pool)
                return;

        if (!page_pool_put(pool))
                return;

        page_pool_disable_direct_recycling(pool);
        page_pool_free_frag(pool);

        if (!page_pool_release(pool))
                return;

        page_pool_detached(pool);
        pool->defer_start = jiffies;
        pool->defer_warn  = jiffies + DEFER_WARN_INTERVAL;

        INIT_DELAYED_WORK(&pool->release_dw, page_pool_release_retry);
        schedule_delayed_work(&pool->release_dw, DEFER_TIME);
}
EXPORT_SYMBOL(page_pool_destroy);

/* Caller must provide appropriate safe context, e.g. NAPI. */
void page_pool_update_nid(struct page_pool *pool, int new_nid)
{
        netmem_ref netmem;

        trace_page_pool_update_nid(pool, new_nid);
        pool->p.nid = new_nid;

        /* Flush pool alloc cache, as refill will check NUMA node */
        while (pool->alloc.count) {
                netmem = pool->alloc.cache[--pool->alloc.count];
                page_pool_return_page(pool, netmem);
        }
}
EXPORT_SYMBOL(page_pool_update_nid);