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	Version: linux-6.0.1 spark-3.0.0 hadoop-3.2.0-src hadoop-3.3.0-src spark-2.4.7 linux-4.15.13 hadoop-2.7.4-src Revert   Change

 /* SPDX-License-Identifier: GPL-2.0
  *
  * page_pool.c
  *  Author: Jesper Dangaard Brouer <netoptimizer@brouer.com>
  *  Copyright (C) 2016 Red Hat, Inc.
  */
 
 #include <linux/types.h>
 #include <linux/kernel.h>
 #include <linux/slab.h>
 #include <linux/device.h>
 
 #include <net/page_pool.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 <trace/events/page_pool.h>
 
 #define DEFER_TIME (msecs_to_jiffies(1000))
 #define DEFER_WARN_INTERVAL (60 * HZ)
 
 #define BIAS_MAX    LONG_MAX
 
 #ifdef CONFIG_PAGE_POOL_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",
 };
 
 bool page_pool_get_stats(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, void *stats)
 {
     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 int page_pool_init(struct page_pool *pool,
               const struct page_pool_params *params)
 {
     unsigned int ring_qsize = 1024; /* Default */
 
     memcpy(&pool->p, params, sizeof(pool->p));
 
     /* Validate only known flags were used */
     if (pool->p.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->p.flags & PP_FLAG_DMA_MAP) {
         if ((pool->p.dma_dir != DMA_FROM_DEVICE) &&
             (pool->p.dma_dir != DMA_BIDIRECTIONAL))
             return -EINVAL;
     }
 
     if (pool->p.flags & PP_FLAG_DMA_SYNC_DEV) {
         /* In order to request DMA-sync-for-device the page
          * needs to be mapped
          */
         if (!(pool->p.flags & PP_FLAG_DMA_MAP))
             return -EINVAL;
 
         if (!pool->p.max_len)
             return -EINVAL;
 
         /* pool->p.offset has to be set according to the address
          * offset used by the DMA engine to start copying rx data
          */
     }
 
     if (PAGE_POOL_DMA_USE_PP_FRAG_COUNT &&
         pool->p.flags & PP_FLAG_PAGE_FRAG)
         return -EINVAL;
 
 #ifdef CONFIG_PAGE_POOL_STATS
     pool->recycle_stats = alloc_percpu(struct page_pool_recycle_stats);
     if (!pool->recycle_stats)
         return -ENOMEM;
 #endif
 
     if (ptr_ring_init(&pool->ring, ring_qsize, GFP_KERNEL) < 0)
         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->p.flags & PP_FLAG_DMA_MAP)
         get_device(pool->p.dev);
 
     return 0;
 }
 
 struct page_pool *page_pool_create(const struct page_pool_params *params)
 {
     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);
     if (err < 0) {
         pr_warn("%s() gave up with errno %d\n", __func__, err);
         kfree(pool);
         return ERR_PTR(err);
     }
 
     return pool;
 }
 EXPORT_SYMBOL(page_pool_create);
 
 static void page_pool_return_page(struct page_pool *pool, struct page *page);
 
 noinline
 static struct page *page_pool_refill_alloc_cache(struct page_pool *pool)
 {
     struct ptr_ring *r = &pool->ring;
     struct page *page;
     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 NULL;
     }
 
     /* 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 {
         page = __ptr_ring_consume(r);
         if (unlikely(!page))
             break;
 
         if (likely(page_to_nid(page) == pref_nid)) {
             pool->alloc.cache[pool->alloc.count++] = page;
         } 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, page);
             alloc_stat_inc(pool, waive);
             page = NULL;
             break;
         }
     } while (pool->alloc.count < PP_ALLOC_CACHE_REFILL);
 
     /* Return last page */
     if (likely(pool->alloc.count > 0)) {
         page = pool->alloc.cache[--pool->alloc.count];
         alloc_stat_inc(pool, refill);
     }
 
     return page;
 }
 
 /* fast path */
 static struct page *__page_pool_get_cached(struct page_pool *pool)
 {
     struct page *page;
 
     /* Caller MUST guarantee safe non-concurrent access, e.g. softirq */
     if (likely(pool->alloc.count)) {
         /* Fast-path */
         page = pool->alloc.cache[--pool->alloc.count];
         alloc_stat_inc(pool, fast);
     } else {
         page = page_pool_refill_alloc_cache(pool);
     }
 
     return page;
 }
 
 static void page_pool_dma_sync_for_device(struct page_pool *pool,
                       struct page *page,
                       unsigned int dma_sync_size)
 {
     dma_addr_t dma_addr = page_pool_get_dma_addr(page);
 
     dma_sync_size = min(dma_sync_size, pool->p.max_len);
     dma_sync_single_range_for_device(pool->p.dev, dma_addr,
                      pool->p.offset, dma_sync_size,
                      pool->p.dma_dir);
 }
 
 static bool page_pool_dma_map(struct page_pool *pool, struct page *page)
 {
     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, page, 0,
                  (PAGE_SIZE << pool->p.order),
                  pool->p.dma_dir, DMA_ATTR_SKIP_CPU_SYNC);
     if (dma_mapping_error(pool->p.dev, dma))
         return false;
 
     page_pool_set_dma_addr(page, dma);
 
     if (pool->p.flags & PP_FLAG_DMA_SYNC_DEV)
         page_pool_dma_sync_for_device(pool, page, pool->p.max_len);
 
     return true;
 }
 
 static void page_pool_set_pp_info(struct page_pool *pool,
                   struct page *page)
 {
     page->pp = pool;
     page->pp_magic |= PP_SIGNATURE;
     if (pool->p.init_callback)
         pool->p.init_callback(page, pool->p.init_arg);
 }
 
 static void page_pool_clear_pp_info(struct page *page)
 {
     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->p.flags & PP_FLAG_DMA_MAP) &&
         unlikely(!page_pool_dma_map(pool, page))) {
         put_page(page);
         return NULL;
     }
 
     alloc_stat_inc(pool, slow_high_order);
     page_pool_set_pp_info(pool, page);
 
     /* Track how many pages are held 'in-flight' */
     pool->pages_state_hold_cnt++;
     trace_page_pool_state_hold(pool, page, pool->pages_state_hold_cnt);
     return page;
 }
 
 /* slow path */
 noinline
 static struct page *__page_pool_alloc_pages_slow(struct page_pool *pool,
                          gfp_t gfp)
 {
     const int bulk = PP_ALLOC_CACHE_REFILL;
     unsigned int pp_flags = pool->p.flags;
     unsigned int pp_order = pool->p.order;
     struct page *page;
     int i, nr_pages;
 
     /* Don't support bulk alloc for high-order pages */
     if (unlikely(pp_order))
         return __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,
                            pool->alloc.cache);
     if (unlikely(!nr_pages))
         return NULL;
 
     /* 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++) {
         page = pool->alloc.cache[i];
         if ((pp_flags & PP_FLAG_DMA_MAP) &&
             unlikely(!page_pool_dma_map(pool, page))) {
             put_page(page);
             continue;
         }
 
         page_pool_set_pp_info(pool, page);
         pool->alloc.cache[pool->alloc.count++] = page;
         /* Track how many pages are held 'in-flight' */
         pool->pages_state_hold_cnt++;
         trace_page_pool_state_hold(pool, page,
                        pool->pages_state_hold_cnt);
     }
 
     /* Return last page */
     if (likely(pool->alloc.count > 0)) {
         page = pool->alloc.cache[--pool->alloc.count];
         alloc_stat_inc(pool, slow);
     } else {
         page = NULL;
     }
 
     /* When page just alloc'ed is should/must have refcnt 1. */
     return page;
 }
 
 /* For using page_pool replace: alloc_pages() API calls, but provide
  * synchronization guarantee for allocation side.
  */
 struct page *page_pool_alloc_pages(struct page_pool *pool, gfp_t gfp)
 {
     struct page *page;
 
     /* Fast-path: Get a page from cache */
     page = __page_pool_get_cached(pool);
     if (page)
         return page;
 
     /* Slow-path: cache empty, do real allocation */
     page = __page_pool_alloc_pages_slow(pool, gfp);
     return page;
 }
 EXPORT_SYMBOL(page_pool_alloc_pages);
 
 /* 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))
 
 static s32 page_pool_inflight(struct page_pool *pool)
 {
     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);
 
     trace_page_pool_release(pool, inflight, hold_cnt, release_cnt);
     WARN(inflight < 0, "Negative(%d) inflight packet-pages", inflight);
 
     return inflight;
 }
 
 /* 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_release_page(struct page_pool *pool, struct page *page)
 {
     dma_addr_t dma;
     int count;
 
     if (!(pool->p.flags & PP_FLAG_DMA_MAP))
         /* Always account for inflight pages, even if we didn't
          * map them
          */
         goto skip_dma_unmap;
 
     dma = page_pool_get_dma_addr(page);
 
     /* 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);
     page_pool_set_dma_addr(page, 0);
 skip_dma_unmap:
     page_pool_clear_pp_info(page);
 
     /* 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, page, count);
 }
 EXPORT_SYMBOL(page_pool_release_page);
 
 /* Return a page to the page allocator, cleaning up our state */
 static void page_pool_return_page(struct page_pool *pool, struct page *page)
 {
     page_pool_release_page(pool, page);
 
     put_page(page);
     /* 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, struct page *page)
 {
     int ret;
     /* BH protection not needed if current is serving softirq */
     if (in_serving_softirq())
         ret = ptr_ring_produce(&pool->ring, page);
     else
         ret = ptr_ring_produce_bh(&pool->ring, page);
 
     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(struct page *page,
                        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++] = page;
     recycle_stat_inc(pool, cached);
     return true;
 }
 
 /* If the page refcnt == 1, this will try to recycle the page.
  * if PP_FLAG_DMA_SYNC_DEV 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 struct page *
 __page_pool_put_page(struct page_pool *pool, struct page *page,
              unsigned int dma_sync_size, bool allow_direct)
 {
     /* 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_ref_count(page) == 1 && !page_is_pfmemalloc(page))) {
         /* Read barrier done in page_ref_count / READ_ONCE */
 
         if (pool->p.flags & PP_FLAG_DMA_SYNC_DEV)
             page_pool_dma_sync_for_device(pool, page,
                               dma_sync_size);
 
         if (allow_direct && in_serving_softirq() &&
             page_pool_recycle_in_cache(page, pool))
             return NULL;
 
         /* Page found as candidate for recycling */
         return page;
     }
     /* 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);
     /* Do not replace this with page_pool_return_page() */
     page_pool_release_page(pool, page);
     put_page(page);
 
     return NULL;
 }
 
 void page_pool_put_defragged_page(struct page_pool *pool, struct page *page,
                   unsigned int dma_sync_size, bool allow_direct)
 {
     page = __page_pool_put_page(pool, page, dma_sync_size, allow_direct);
     if (page && !page_pool_recycle_in_ring(pool, page)) {
         /* Cache full, fallback to free pages */
         recycle_stat_inc(pool, ring_full);
         page_pool_return_page(pool, page);
     }
 }
 EXPORT_SYMBOL(page_pool_put_defragged_page);
 
 /* Caller must not use data area after call, as this function overwrites it */
 void page_pool_put_page_bulk(struct page_pool *pool, void **data,
                  int count)
 {
     int i, bulk_len = 0;
 
     for (i = 0; i < count; i++) {
         struct page *page = virt_to_head_page(data[i]);
 
         /* It is not the last user for the page frag case */
         if (!page_pool_is_last_frag(pool, page))
             continue;
 
         page = __page_pool_put_page(pool, page, -1, false);
         /* Approved for bulk recycling in ptr_ring cache */
         if (page)
             data[bulk_len++] = page;
     }
 
     if (unlikely(!bulk_len))
         return;
 
     /* Bulk producer into ptr_ring page_pool cache */
     page_pool_ring_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_ring_unlock(pool);
 
     /* 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, data[i]);
 }
 EXPORT_SYMBOL(page_pool_put_page_bulk);
 
 static struct page *page_pool_drain_frag(struct page_pool *pool,
                      struct page *page)
 {
     long drain_count = BIAS_MAX - pool->frag_users;
 
     /* Some user is still using the page frag */
     if (likely(page_pool_defrag_page(page, drain_count)))
         return NULL;
 
     if (page_ref_count(page) == 1 && !page_is_pfmemalloc(page)) {
         if (pool->p.flags & PP_FLAG_DMA_SYNC_DEV)
             page_pool_dma_sync_for_device(pool, page, -1);
 
         return page;
     }
 
     page_pool_return_page(pool, page);
     return NULL;
 }
 
 static void page_pool_free_frag(struct page_pool *pool)
 {
     long drain_count = BIAS_MAX - pool->frag_users;
     struct page *page = pool->frag_page;
 
     pool->frag_page = NULL;
 
     if (!page || page_pool_defrag_page(page, drain_count))
         return;
 
     page_pool_return_page(pool, page);
 }
 
 struct page *page_pool_alloc_frag(struct page_pool *pool,
                   unsigned int *offset,
                   unsigned int size, gfp_t gfp)
 {
     unsigned int max_size = PAGE_SIZE << pool->p.order;
     struct page *page = pool->frag_page;
 
     if (WARN_ON(!(pool->p.flags & PP_FLAG_PAGE_FRAG) ||
             size > max_size))
         return NULL;
 
     size = ALIGN(size, dma_get_cache_alignment());
     *offset = pool->frag_offset;
 
     if (page && *offset + size > max_size) {
         page = page_pool_drain_frag(pool, page);
         if (page) {
             alloc_stat_inc(pool, fast);
             goto frag_reset;
         }
     }
 
     if (!page) {
         page = page_pool_alloc_pages(pool, gfp);
         if (unlikely(!page)) {
             pool->frag_page = NULL;
             return NULL;
         }
 
         pool->frag_page = page;
 
 frag_reset:
         pool->frag_users = 1;
         *offset = 0;
         pool->frag_offset = size;
         page_pool_fragment_page(page, BIAS_MAX);
         return page;
     }
 
     pool->frag_users++;
     pool->frag_offset = *offset + size;
     alloc_stat_inc(pool, fast);
     return page;
 }
 EXPORT_SYMBOL(page_pool_alloc_frag);
 
 static void page_pool_empty_ring(struct page_pool *pool)
 {
     struct page *page;
 
     /* Empty recycle ring */
     while ((page = ptr_ring_consume_bh(&pool->ring))) {
         /* Verify the refcnt invariant of cached pages */
         if (!(page_ref_count(page) == 1))
             pr_crit("%s() page_pool refcnt %d violation\n",
                 __func__, page_ref_count(page));
 
         page_pool_return_page(pool, page);
     }
 }
 
 static void page_pool_free(struct page_pool *pool)
 {
     if (pool->disconnect)
         pool->disconnect(pool);
 
     ptr_ring_cleanup(&pool->ring, NULL);
 
     if (pool->p.flags & PP_FLAG_DMA_MAP)
         put_device(pool->p.dev);
 
 #ifdef CONFIG_PAGE_POOL_STATS
     free_percpu(pool->recycle_stats);
 #endif
     kfree(pool);
 }
 
 static void page_pool_empty_alloc_cache_once(struct page_pool *pool)
 {
     struct page *page;
 
     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) {
         page = pool->alloc.cache[--pool->alloc.count];
         page_pool_return_page(pool, page);
     }
 }
 
 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);
     if (!inflight)
         page_pool_free(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);
     int inflight;
 
     inflight = page_pool_release(pool);
     if (!inflight)
         return;
 
     /* Periodic warning */
     if (time_after_eq(jiffies, pool->defer_warn)) {
         int sec = (s32)((u32)jiffies - (u32)pool->defer_start) / HZ;
 
         pr_warn("%s() stalled pool shutdown %d inflight %d sec\n",
             __func__, 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 *),
                struct xdp_mem_info *mem)
 {
     refcount_inc(&pool->user_cnt);
     pool->disconnect = disconnect;
     pool->xdp_mem_id = mem->id;
 }
 
 void page_pool_destroy(struct page_pool *pool)
 {
     if (!pool)
         return;
 
     if (!page_pool_put(pool))
         return;
 
     page_pool_free_frag(pool);
 
     if (!page_pool_release(pool))
         return;
 
     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)
 {
     struct page *page;
 
     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) {
         page = pool->alloc.cache[--pool->alloc.count];
         page_pool_return_page(pool, page);
     }
 }
 EXPORT_SYMBOL(page_pool_update_nid);
 
 bool page_pool_return_skb_page(struct page *page)
 {
     struct page_pool *pp;
 
     page = compound_head(page);
 
     /* page->pp_magic is OR'ed with PP_SIGNATURE after the allocation
      * in order to preserve any existing bits, such as bit 0 for the
      * head page of compound page and bit 1 for pfmemalloc page, so
      * mask those bits for freeing side when doing below checking,
      * and page_is_pfmemalloc() is checked in __page_pool_put_page()
      * to avoid recycling the pfmemalloc page.
      */
     if (unlikely((page->pp_magic & ~0x3UL) != PP_SIGNATURE))
         return false;
 
     pp = page->pp;
 
     /* Driver set this to memory recycling info. Reset it on recycle.
      * This will *not* work for NIC using a split-page memory model.
      * The page will be returned to the pool here regardless of the
      * 'flipped' fragment being in use or not.
      */
     page_pool_put_full_page(pp, page, false);
 
     return true;
 }
 EXPORT_SYMBOL(page_pool_return_skb_page);

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