net/core/page_pool.c

   1 /* SPDX-License-Identifier: GPL-2.0
   2  *
   3  * page_pool.c
   4  *      Author: Jesper Dangaard Brouer <netoptimizer@brouer.com>
   5  *      Copyright (C) 2016 Red Hat, Inc.
   6  */
   7
   8 #include <linux/types.h>
   9 #include <linux/kernel.h>
  10 #include <linux/slab.h>
  11 #include <linux/device.h>
  12
  13 #include <net/page_pool.h>
  14 #include <net/xdp.h>
  15
  16 #include <linux/dma-direction.h>
  17 #include <linux/dma-mapping.h>
  18 #include <linux/page-flags.h>
  19 #include <linux/mm.h> /* for __put_page() */
  20 #include <linux/poison.h>
  21
  22 #include <trace/events/page_pool.h>
  23
  24 #define DEFER_TIME (msecs_to_jiffies(1000))
  25 #define DEFER_WARN_INTERVAL (60 * HZ)
  26
  27 static int page_pool_init(struct page_pool *pool,
  28                           const struct page_pool_params *params)
  29 {
  30         unsigned int ring_qsize = 1024; /* Default */
  31
  32         memcpy(&pool->p, params, sizeof(pool->p));
  33
  34         /* Validate only known flags were used */
  35         if (pool->p.flags & ~(PP_FLAG_ALL))
  36                 return -EINVAL;
  37
  38         if (pool->p.pool_size)
  39                 ring_qsize = pool->p.pool_size;
  40
  41         /* Sanity limit mem that can be pinned down */
  42         if (ring_qsize > 32768)
  43                 return -E2BIG;
  44
  45         /* DMA direction is either DMA_FROM_DEVICE or DMA_BIDIRECTIONAL.
  46          * DMA_BIDIRECTIONAL is for allowing page used for DMA sending,
  47          * which is the XDP_TX use-case.
  48          */
  49         if (pool->p.flags & PP_FLAG_DMA_MAP) {
  50                 if ((pool->p.dma_dir != DMA_FROM_DEVICE) &&
  51                     (pool->p.dma_dir != DMA_BIDIRECTIONAL))
  52                         return -EINVAL;
  53         }
  54
  55         if (pool->p.flags & PP_FLAG_DMA_SYNC_DEV) {
  56                 /* In order to request DMA-sync-for-device the page
  57                  * needs to be mapped
  58                  */
  59                 if (!(pool->p.flags & PP_FLAG_DMA_MAP))
  60                         return -EINVAL;
  61
  62                 if (!pool->p.max_len)
  63                         return -EINVAL;
  64
  65                 /* pool->p.offset has to be set according to the address
  66                  * offset used by the DMA engine to start copying rx data
  67                  */
  68         }
  69
  70         if (ptr_ring_init(&pool->ring, ring_qsize, GFP_KERNEL) < 0)
  71                 return -ENOMEM;
  72
  73         atomic_set(&pool->pages_state_release_cnt, 0);
  74
  75         /* Driver calling page_pool_create() also call page_pool_destroy() */
  76         refcount_set(&pool->user_cnt, 1);
  77
  78         if (pool->p.flags & PP_FLAG_DMA_MAP)
  79                 get_device(pool->p.dev);
  80
  81         return 0;
  82 }
  83
  84 struct page_pool *page_pool_create(const struct page_pool_params *params)
  85 {
  86         struct page_pool *pool;
  87         int err;
  88
  89         pool = kzalloc_node(sizeof(*pool), GFP_KERNEL, params->nid);
  90         if (!pool)
  91                 return ERR_PTR(-ENOMEM);
  92
  93         err = page_pool_init(pool, params);
  94         if (err < 0) {
  95                 pr_warn("%s() gave up with errno %d\n", __func__, err);
  96                 kfree(pool);
  97                 return ERR_PTR(err);
  98         }
  99
 100         return pool;
 101 }
 102 EXPORT_SYMBOL(page_pool_create);
 103
 104 static void page_pool_return_page(struct page_pool *pool, struct page *page);
 105
 106 noinline
 107 static struct page *page_pool_refill_alloc_cache(struct page_pool *pool)
 108 {
 109         struct ptr_ring *r = &pool->ring;
 110         struct page *page;
 111         int pref_nid; /* preferred NUMA node */
 112
 113         /* Quicker fallback, avoid locks when ring is empty */
 114         if (__ptr_ring_empty(r))
 115                 return NULL;
 116
 117         /* Softirq guarantee CPU and thus NUMA node is stable. This,
 118          * assumes CPU refilling driver RX-ring will also run RX-NAPI.
 119          */
 120 #ifdef CONFIG_NUMA
 121         pref_nid = (pool->p.nid == NUMA_NO_NODE) ? numa_mem_id() : pool->p.nid;
 122 #else
 123         /* Ignore pool->p.nid setting if !CONFIG_NUMA, helps compiler */
 124         pref_nid = numa_mem_id(); /* will be zero like page_to_nid() */
 125 #endif
 126
 127         /* Slower-path: Get pages from locked ring queue */
 128         spin_lock(&r->consumer_lock);
 129
 130         /* Refill alloc array, but only if NUMA match */
 131         do {
 132                 page = __ptr_ring_consume(r);
 133                 if (unlikely(!page))
 134                         break;
 135
 136                 if (likely(page_to_nid(page) == pref_nid)) {
 137                         pool->alloc.cache[pool->alloc.count++] = page;
 138                 } else {
 139                         /* NUMA mismatch;
 140                          * (1) release 1 page to page-allocator and
 141                          * (2) break out to fallthrough to alloc_pages_node.
 142                          * This limit stress on page buddy alloactor.
 143                          */
 144                         page_pool_return_page(pool, page);
 145                         page = NULL;
 146                         break;
 147                 }
 148         } while (pool->alloc.count < PP_ALLOC_CACHE_REFILL);
 149
 150         /* Return last page */
 151         if (likely(pool->alloc.count > 0))
 152                 page = pool->alloc.cache[--pool->alloc.count];
 153
 154         spin_unlock(&r->consumer_lock);
 155         return page;
 156 }
 157
 158 /* fast path */
 159 static struct page *__page_pool_get_cached(struct page_pool *pool)
 160 {
 161         struct page *page;
 162
 163         /* Caller MUST guarantee safe non-concurrent access, e.g. softirq */
 164         if (likely(pool->alloc.count)) {
 165                 /* Fast-path */
 166                 page = pool->alloc.cache[--pool->alloc.count];
 167         } else {
 168                 page = page_pool_refill_alloc_cache(pool);
 169         }
 170
 171         return page;
 172 }
 173
 174 static void page_pool_dma_sync_for_device(struct page_pool *pool,
 175                                           struct page *page,
 176                                           unsigned int dma_sync_size)
 177 {
 178         dma_addr_t dma_addr = page_pool_get_dma_addr(page);
 179
 180         dma_sync_size = min(dma_sync_size, pool->p.max_len);
 181         dma_sync_single_range_for_device(pool->p.dev, dma_addr,
 182                                          pool->p.offset, dma_sync_size,
 183                                          pool->p.dma_dir);
 184 }
 185
 186 static bool page_pool_dma_map(struct page_pool *pool, struct page *page)
 187 {
 188         dma_addr_t dma;
 189
 190         /* Setup DMA mapping: use 'struct page' area for storing DMA-addr
 191          * since dma_addr_t can be either 32 or 64 bits and does not always fit
 192          * into page private data (i.e 32bit cpu with 64bit DMA caps)
 193          * This mapping is kept for lifetime of page, until leaving pool.
 194          */
 195         dma = dma_map_page_attrs(pool->p.dev, page, 0,
 196                                  (PAGE_SIZE << pool->p.order),
 197                                  pool->p.dma_dir, DMA_ATTR_SKIP_CPU_SYNC);
 198         if (dma_mapping_error(pool->p.dev, dma))
 199                 return false;
 200
 201         page_pool_set_dma_addr(page, dma);
 202
 203         if (pool->p.flags & PP_FLAG_DMA_SYNC_DEV)
 204                 page_pool_dma_sync_for_device(pool, page, pool->p.max_len);
 205
 206         return true;
 207 }
 208
 209 static struct page *__page_pool_alloc_page_order(struct page_pool *pool,
 210                                                  gfp_t gfp)
 211 {
 212         struct page *page;
 213
 214         gfp |= __GFP_COMP;
 215         page = alloc_pages_node(pool->p.nid, gfp, pool->p.order);
 216         if (unlikely(!page))
 217                 return NULL;
 218
 219         if ((pool->p.flags & PP_FLAG_DMA_MAP) &&
 220             unlikely(!page_pool_dma_map(pool, page))) {
 221                 put_page(page);
 222                 return NULL;
 223         }
 224
 225         page->pp_magic |= PP_SIGNATURE;
 226
 227         /* Track how many pages are held 'in-flight' */
 228         pool->pages_state_hold_cnt++;
 229         trace_page_pool_state_hold(pool, page, pool->pages_state_hold_cnt);
 230         return page;
 231 }
 232
 233 /* slow path */
 234 noinline
 235 static struct page *__page_pool_alloc_pages_slow(struct page_pool *pool,
 236                                                  gfp_t gfp)
 237 {
 238         const int bulk = PP_ALLOC_CACHE_REFILL;
 239         unsigned int pp_flags = pool->p.flags;
 240         unsigned int pp_order = pool->p.order;
 241         struct page *page;
 242         int i, nr_pages;
 243
 244         /* Don't support bulk alloc for high-order pages */
 245         if (unlikely(pp_order))
 246                 return __page_pool_alloc_page_order(pool, gfp);
 247
 248         /* Unnecessary as alloc cache is empty, but guarantees zero count */
 249         if (unlikely(pool->alloc.count > 0))
 250                 return pool->alloc.cache[--pool->alloc.count];
 251
 252         /* Mark empty alloc.cache slots "empty" for alloc_pages_bulk_array */
 253         memset(&pool->alloc.cache, 0, sizeof(void *) * bulk);
 254
 255         nr_pages = alloc_pages_bulk_array(gfp, bulk, pool->alloc.cache);
 256         if (unlikely(!nr_pages))
 257                 return NULL;
 258
 259         /* Pages have been filled into alloc.cache array, but count is zero and
 260          * page element have not been (possibly) DMA mapped.
 261          */
 262         for (i = 0; i < nr_pages; i++) {
 263                 page = pool->alloc.cache[i];
 264                 if ((pp_flags & PP_FLAG_DMA_MAP) &&
 265                     unlikely(!page_pool_dma_map(pool, page))) {
 266                         put_page(page);
 267                         continue;
 268                 }
 269                 page->pp_magic |= PP_SIGNATURE;
 270                 pool->alloc.cache[pool->alloc.count++] = page;
 271                 /* Track how many pages are held 'in-flight' */
 272                 pool->pages_state_hold_cnt++;
 273                 trace_page_pool_state_hold(pool, page,
 274                                            pool->pages_state_hold_cnt);
 275         }
 276
 277         /* Return last page */
 278         if (likely(pool->alloc.count > 0))
 279                 page = pool->alloc.cache[--pool->alloc.count];
 280         else
 281                 page = NULL;
 282
 283         /* When page just alloc'ed is should/must have refcnt 1. */
 284         return page;
 285 }
 286
 287 /* For using page_pool replace: alloc_pages() API calls, but provide
 288  * synchronization guarantee for allocation side.
 289  */
 290 struct page *page_pool_alloc_pages(struct page_pool *pool, gfp_t gfp)
 291 {
 292         struct page *page;
 293
 294         /* Fast-path: Get a page from cache */
 295         page = __page_pool_get_cached(pool);
 296         if (page)
 297                 return page;
 298
 299         /* Slow-path: cache empty, do real allocation */
 300         page = __page_pool_alloc_pages_slow(pool, gfp);
 301         return page;
 302 }
 303 EXPORT_SYMBOL(page_pool_alloc_pages);
 304
 305 /* Calculate distance between two u32 values, valid if distance is below 2^(31)
 306  *  https://en.wikipedia.org/wiki/Serial_number_arithmetic#General_Solution
 307  */
 308 #define _distance(a, b) (s32)((a) - (b))
 309
 310 static s32 page_pool_inflight(struct page_pool *pool)
 311 {
 312         u32 release_cnt = atomic_read(&pool->pages_state_release_cnt);
 313         u32 hold_cnt = READ_ONCE(pool->pages_state_hold_cnt);
 314         s32 inflight;
 315
 316         inflight = _distance(hold_cnt, release_cnt);
 317
 318         trace_page_pool_release(pool, inflight, hold_cnt, release_cnt);
 319         WARN(inflight < 0, "Negative(%d) inflight packet-pages", inflight);
 320
 321         return inflight;
 322 }
 323
 324 /* Disconnects a page (from a page_pool).  API users can have a need
 325  * to disconnect a page (from a page_pool), to allow it to be used as
 326  * a regular page (that will eventually be returned to the normal
 327  * page-allocator via put_page).
 328  */
 329 void page_pool_release_page(struct page_pool *pool, struct page *page)
 330 {
 331         dma_addr_t dma;
 332         int count;
 333
 334         if (!(pool->p.flags & PP_FLAG_DMA_MAP))
 335                 /* Always account for inflight pages, even if we didn't
 336                  * map them
 337                  */
 338                 goto skip_dma_unmap;
 339
 340         dma = page_pool_get_dma_addr(page);
 341
 342         /* When page is unmapped, it cannot be returned to our pool */
 343         dma_unmap_page_attrs(pool->p.dev, dma,
 344                              PAGE_SIZE << pool->p.order, pool->p.dma_dir,
 345                              DMA_ATTR_SKIP_CPU_SYNC);
 346         page_pool_set_dma_addr(page, 0);
 347 skip_dma_unmap:
 348         page->pp_magic = 0;
 349
 350         /* This may be the last page returned, releasing the pool, so
 351          * it is not safe to reference pool afterwards.
 352          */
 353         count = atomic_inc_return(&pool->pages_state_release_cnt);
 354         trace_page_pool_state_release(pool, page, count);
 355 }
 356 EXPORT_SYMBOL(page_pool_release_page);
 357
 358 /* Return a page to the page allocator, cleaning up our state */
 359 static void page_pool_return_page(struct page_pool *pool, struct page *page)
 360 {
 361         page_pool_release_page(pool, page);
 362
 363         put_page(page);
 364         /* An optimization would be to call __free_pages(page, pool->p.order)
 365          * knowing page is not part of page-cache (thus avoiding a
 366          * __page_cache_release() call).
 367          */
 368 }
 369
 370 static bool page_pool_recycle_in_ring(struct page_pool *pool, struct page *page)
 371 {
 372         int ret;
 373         /* BH protection not needed if current is serving softirq */
 374         if (in_serving_softirq())
 375                 ret = ptr_ring_produce(&pool->ring, page);
 376         else
 377                 ret = ptr_ring_produce_bh(&pool->ring, page);
 378
 379         return (ret == 0) ? true : false;
 380 }
 381
 382 /* Only allow direct recycling in special circumstances, into the
 383  * alloc side cache.  E.g. during RX-NAPI processing for XDP_DROP use-case.
 384  *
 385  * Caller must provide appropriate safe context.
 386  */
 387 static bool page_pool_recycle_in_cache(struct page *page,
 388                                        struct page_pool *pool)
 389 {
 390         if (unlikely(pool->alloc.count == PP_ALLOC_CACHE_SIZE))
 391                 return false;
 392
 393         /* Caller MUST have verified/know (page_ref_count(page) == 1) */
 394         pool->alloc.cache[pool->alloc.count++] = page;
 395         return true;
 396 }
 397
 398 /* If the page refcnt == 1, this will try to recycle the page.
 399  * if PP_FLAG_DMA_SYNC_DEV is set, we'll try to sync the DMA area for
 400  * the configured size min(dma_sync_size, pool->max_len).
 401  * If the page refcnt != 1, then the page will be returned to memory
 402  * subsystem.
 403  */
 404 static __always_inline struct page *
 405 __page_pool_put_page(struct page_pool *pool, struct page *page,
 406                      unsigned int dma_sync_size, bool allow_direct)
 407 {
 408         /* This allocator is optimized for the XDP mode that uses
 409          * one-frame-per-page, but have fallbacks that act like the
 410          * regular page allocator APIs.
 411          *
 412          * refcnt == 1 means page_pool owns page, and can recycle it.
 413          *
 414          * page is NOT reusable when allocated when system is under
 415          * some pressure. (page_is_pfmemalloc)
 416          */
 417         if (likely(page_ref_count(page) == 1 && !page_is_pfmemalloc(page))) {
 418                 /* Read barrier done in page_ref_count / READ_ONCE */
 419
 420                 if (pool->p.flags & PP_FLAG_DMA_SYNC_DEV)
 421                         page_pool_dma_sync_for_device(pool, page,
 422                                                       dma_sync_size);
 423
 424                 if (allow_direct && in_serving_softirq() &&
 425                     page_pool_recycle_in_cache(page, pool))
 426                         return NULL;
 427
 428                 /* Page found as candidate for recycling */
 429                 return page;
 430         }
 431         /* Fallback/non-XDP mode: API user have elevated refcnt.
 432          *
 433          * Many drivers split up the page into fragments, and some
 434          * want to keep doing this to save memory and do refcnt based
 435          * recycling. Support this use case too, to ease drivers
 436          * switching between XDP/non-XDP.
 437          *
 438          * In-case page_pool maintains the DMA mapping, API user must
 439          * call page_pool_put_page once.  In this elevated refcnt
 440          * case, the DMA is unmapped/released, as driver is likely
 441          * doing refcnt based recycle tricks, meaning another process
 442          * will be invoking put_page.
 443          */
 444         /* Do not replace this with page_pool_return_page() */
 445         page_pool_release_page(pool, page);
 446         put_page(page);
 447
 448         return NULL;
 449 }
 450
 451 void page_pool_put_page(struct page_pool *pool, struct page *page,
 452                         unsigned int dma_sync_size, bool allow_direct)
 453 {
 454         page = __page_pool_put_page(pool, page, dma_sync_size, allow_direct);
 455         if (page && !page_pool_recycle_in_ring(pool, page)) {
 456                 /* Cache full, fallback to free pages */
 457                 page_pool_return_page(pool, page);
 458         }
 459 }
 460 EXPORT_SYMBOL(page_pool_put_page);
 461
 462 /* Caller must not use data area after call, as this function overwrites it */
 463 void page_pool_put_page_bulk(struct page_pool *pool, void **data,
 464                              int count)
 465 {
 466         int i, bulk_len = 0;
 467
 468         for (i = 0; i < count; i++) {
 469                 struct page *page = virt_to_head_page(data[i]);
 470
 471                 page = __page_pool_put_page(pool, page, -1, false);
 472                 /* Approved for bulk recycling in ptr_ring cache */
 473                 if (page)
 474                         data[bulk_len++] = page;
 475         }
 476
 477         if (unlikely(!bulk_len))
 478                 return;
 479
 480         /* Bulk producer into ptr_ring page_pool cache */
 481         page_pool_ring_lock(pool);
 482         for (i = 0; i < bulk_len; i++) {
 483                 if (__ptr_ring_produce(&pool->ring, data[i]))
 484                         break; /* ring full */
 485         }
 486         page_pool_ring_unlock(pool);
 487
 488         /* Hopefully all pages was return into ptr_ring */
 489         if (likely(i == bulk_len))
 490                 return;
 491
 492         /* ptr_ring cache full, free remaining pages outside producer lock
 493          * since put_page() with refcnt == 1 can be an expensive operation
 494          */
 495         for (; i < bulk_len; i++)
 496                 page_pool_return_page(pool, data[i]);
 497 }
 498 EXPORT_SYMBOL(page_pool_put_page_bulk);
 499
 500 static void page_pool_empty_ring(struct page_pool *pool)
 501 {
 502         struct page *page;
 503
 504         /* Empty recycle ring */
 505         while ((page = ptr_ring_consume_bh(&pool->ring))) {
 506                 /* Verify the refcnt invariant of cached pages */
 507                 if (!(page_ref_count(page) == 1))
 508                         pr_crit("%s() page_pool refcnt %d violation\n",
 509                                 __func__, page_ref_count(page));
 510
 511                 page_pool_return_page(pool, page);
 512         }
 513 }
 514
 515 static void page_pool_free(struct page_pool *pool)
 516 {
 517         if (pool->disconnect)
 518                 pool->disconnect(pool);
 519
 520         ptr_ring_cleanup(&pool->ring, NULL);
 521
 522         if (pool->p.flags & PP_FLAG_DMA_MAP)
 523                 put_device(pool->p.dev);
 524
 525         kfree(pool);
 526 }
 527
 528 static void page_pool_empty_alloc_cache_once(struct page_pool *pool)
 529 {
 530         struct page *page;
 531
 532         if (pool->destroy_cnt)
 533                 return;
 534
 535         /* Empty alloc cache, assume caller made sure this is
 536          * no-longer in use, and page_pool_alloc_pages() cannot be
 537          * call concurrently.
 538          */
 539         while (pool->alloc.count) {
 540                 page = pool->alloc.cache[--pool->alloc.count];
 541                 page_pool_return_page(pool, page);
 542         }
 543 }
 544
 545 static void page_pool_scrub(struct page_pool *pool)
 546 {
 547         page_pool_empty_alloc_cache_once(pool);
 548         pool->destroy_cnt++;
 549
 550         /* No more consumers should exist, but producers could still
 551          * be in-flight.
 552          */
 553         page_pool_empty_ring(pool);
 554 }
 555
 556 static int page_pool_release(struct page_pool *pool)
 557 {
 558         int inflight;
 559
 560         page_pool_scrub(pool);
 561         inflight = page_pool_inflight(pool);
 562         if (!inflight)
 563                 page_pool_free(pool);
 564
 565         return inflight;
 566 }
 567
 568 static void page_pool_release_retry(struct work_struct *wq)
 569 {
 570         struct delayed_work *dwq = to_delayed_work(wq);
 571         struct page_pool *pool = container_of(dwq, typeof(*pool), release_dw);
 572         int inflight;
 573
 574         inflight = page_pool_release(pool);
 575         if (!inflight)
 576                 return;
 577
 578         /* Periodic warning */
 579         if (time_after_eq(jiffies, pool->defer_warn)) {
 580                 int sec = (s32)((u32)jiffies - (u32)pool->defer_start) / HZ;
 581
 582                 pr_warn("%s() stalled pool shutdown %d inflight %d sec\n",
 583                         __func__, inflight, sec);
 584                 pool->defer_warn = jiffies + DEFER_WARN_INTERVAL;
 585         }
 586
 587         /* Still not ready to be disconnected, retry later */
 588         schedule_delayed_work(&pool->release_dw, DEFER_TIME);
 589 }
 590
 591 void page_pool_use_xdp_mem(struct page_pool *pool, void (*disconnect)(void *))
 592 {
 593         refcount_inc(&pool->user_cnt);
 594         pool->disconnect = disconnect;
 595 }
 596
 597 void page_pool_destroy(struct page_pool *pool)
 598 {
 599         if (!pool)
 600                 return;
 601
 602         if (!page_pool_put(pool))
 603                 return;
 604
 605         if (!page_pool_release(pool))
 606                 return;
 607
 608         pool->defer_start = jiffies;
 609         pool->defer_warn  = jiffies + DEFER_WARN_INTERVAL;
 610
 611         INIT_DELAYED_WORK(&pool->release_dw, page_pool_release_retry);
 612         schedule_delayed_work(&pool->release_dw, DEFER_TIME);
 613 }
 614 EXPORT_SYMBOL(page_pool_destroy);
 615
 616 /* Caller must provide appropriate safe context, e.g. NAPI. */
 617 void page_pool_update_nid(struct page_pool *pool, int new_nid)
 618 {
 619         struct page *page;
 620
 621         trace_page_pool_update_nid(pool, new_nid);
 622         pool->p.nid = new_nid;
 623
 624         /* Flush pool alloc cache, as refill will check NUMA node */
 625         while (pool->alloc.count) {
 626                 page = pool->alloc.cache[--pool->alloc.count];
 627                 page_pool_return_page(pool, page);
 628         }
 629 }
 630 EXPORT_SYMBOL(page_pool_update_nid);
 631
 632 bool page_pool_return_skb_page(struct page *page)
 633 {
 634         struct page_pool *pp;
 635
 636         page = compound_head(page);
 637
 638         /* page->pp_magic is OR'ed with PP_SIGNATURE after the allocation
 639          * in order to preserve any existing bits, such as bit 0 for the
 640          * head page of compound page and bit 1 for pfmemalloc page, so
 641          * mask those bits for freeing side when doing below checking,
 642          * and page_is_pfmemalloc() is checked in __page_pool_put_page()
 643          * to avoid recycling the pfmemalloc page.
 644          */
 645         if (unlikely((page->pp_magic & ~0x3UL) != PP_SIGNATURE))
 646                 return false;
 647
 648         pp = page->pp;
 649
 650         /* Driver set this to memory recycling info. Reset it on recycle.
 651          * This will *not* work for NIC using a split-page memory model.
 652          * The page will be returned to the pool here regardless of the
 653          * 'flipped' fragment being in use or not.
 654          */
 655         page->pp = NULL;
 656         page_pool_put_full_page(pp, page, false);
 657
 658         return true;
 659 }
 660 EXPORT_SYMBOL(page_pool_return_skb_page);