net/core/page_pool.c

   1 /* SPDX-License-Identifier: GPL-2.0
   2  *
   3  * page_pool.c
   4  *      Author: Jesper Dangaard Brouer <[email protected]>
   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 <linux/dma-direction.h>
  15 #include <linux/dma-mapping.h>
  16 #include <linux/page-flags.h>
  17 #include <linux/mm.h> /* for __put_page() */
  18
  19 #include <trace/events/page_pool.h>
  20
  21 static int page_pool_init(struct page_pool *pool,
  22                           const struct page_pool_params *params)
  23 {
  24         unsigned int ring_qsize = 1024; /* Default */
  25
  26         memcpy(&pool->p, params, sizeof(pool->p));
  27
  28         /* Validate only known flags were used */
  29         if (pool->p.flags & ~(PP_FLAG_ALL))
  30                 return -EINVAL;
  31
  32         if (pool->p.pool_size)
  33                 ring_qsize = pool->p.pool_size;
  34
  35         /* Sanity limit mem that can be pinned down */
  36         if (ring_qsize > 32768)
  37                 return -E2BIG;
  38
  39         /* DMA direction is either DMA_FROM_DEVICE or DMA_BIDIRECTIONAL.
  40          * DMA_BIDIRECTIONAL is for allowing page used for DMA sending,
  41          * which is the XDP_TX use-case.
  42          */
  43         if ((pool->p.dma_dir != DMA_FROM_DEVICE) &&
  44             (pool->p.dma_dir != DMA_BIDIRECTIONAL))
  45                 return -EINVAL;
  46
  47         if (ptr_ring_init(&pool->ring, ring_qsize, GFP_KERNEL) < 0)
  48                 return -ENOMEM;
  49
  50         atomic_set(&pool->pages_state_release_cnt, 0);
  51
  52         if (pool->p.flags & PP_FLAG_DMA_MAP)
  53                 get_device(pool->p.dev);
  54
  55         return 0;
  56 }
  57
  58 struct page_pool *page_pool_create(const struct page_pool_params *params)
  59 {
  60         struct page_pool *pool;
  61         int err = 0;
  62
  63         pool = kzalloc_node(sizeof(*pool), GFP_KERNEL, params->nid);
  64         if (!pool)
  65                 return ERR_PTR(-ENOMEM);
  66
  67         err = page_pool_init(pool, params);
  68         if (err < 0) {
  69                 pr_warn("%s() gave up with errno %d\n", __func__, err);
  70                 kfree(pool);
  71                 return ERR_PTR(err);
  72         }
  73         return pool;
  74 }
  75 EXPORT_SYMBOL(page_pool_create);
  76
  77 /* fast path */
  78 static struct page *__page_pool_get_cached(struct page_pool *pool)
  79 {
  80         struct ptr_ring *r = &pool->ring;
  81         struct page *page;
  82
  83         /* Quicker fallback, avoid locks when ring is empty */
  84         if (__ptr_ring_empty(r))
  85                 return NULL;
  86
  87         /* Test for safe-context, caller should provide this guarantee */
  88         if (likely(in_serving_softirq())) {
  89                 if (likely(pool->alloc.count)) {
  90                         /* Fast-path */
  91                         page = pool->alloc.cache[--pool->alloc.count];
  92                         return page;
  93                 }
  94                 /* Slower-path: Alloc array empty, time to refill
  95                  *
  96                  * Open-coded bulk ptr_ring consumer.
  97                  *
  98                  * Discussion: the ring consumer lock is not really
  99                  * needed due to the softirq/NAPI protection, but
 100                  * later need the ability to reclaim pages on the
 101                  * ring. Thus, keeping the locks.
 102                  */
 103                 spin_lock(&r->consumer_lock);
 104                 while ((page = __ptr_ring_consume(r))) {
 105                         if (pool->alloc.count == PP_ALLOC_CACHE_REFILL)
 106                                 break;
 107                         pool->alloc.cache[pool->alloc.count++] = page;
 108                 }
 109                 spin_unlock(&r->consumer_lock);
 110                 return page;
 111         }
 112
 113         /* Slow-path: Get page from locked ring queue */
 114         page = ptr_ring_consume(&pool->ring);
 115         return page;
 116 }
 117
 118 /* slow path */
 119 noinline
 120 static struct page *__page_pool_alloc_pages_slow(struct page_pool *pool,
 121                                                  gfp_t _gfp)
 122 {
 123         struct page *page;
 124         gfp_t gfp = _gfp;
 125         dma_addr_t dma;
 126
 127         /* We could always set __GFP_COMP, and avoid this branch, as
 128          * prep_new_page() can handle order-0 with __GFP_COMP.
 129          */
 130         if (pool->p.order)
 131                 gfp |= __GFP_COMP;
 132
 133         /* FUTURE development:
 134          *
 135          * Current slow-path essentially falls back to single page
 136          * allocations, which doesn't improve performance.  This code
 137          * need bulk allocation support from the page allocator code.
 138          */
 139
 140         /* Cache was empty, do real allocation */
 141         page = alloc_pages_node(pool->p.nid, gfp, pool->p.order);
 142         if (!page)
 143                 return NULL;
 144
 145         if (!(pool->p.flags & PP_FLAG_DMA_MAP))
 146                 goto skip_dma_map;
 147
 148         /* Setup DMA mapping: use 'struct page' area for storing DMA-addr
 149          * since dma_addr_t can be either 32 or 64 bits and does not always fit
 150          * into page private data (i.e 32bit cpu with 64bit DMA caps)
 151          * This mapping is kept for lifetime of page, until leaving pool.
 152          */
 153         dma = dma_map_page_attrs(pool->p.dev, page, 0,
 154                                  (PAGE_SIZE << pool->p.order),
 155                                  pool->p.dma_dir, DMA_ATTR_SKIP_CPU_SYNC);
 156         if (dma_mapping_error(pool->p.dev, dma)) {
 157                 put_page(page);
 158                 return NULL;
 159         }
 160         page->dma_addr = dma;
 161
 162 skip_dma_map:
 163         /* Track how many pages are held 'in-flight' */
 164         pool->pages_state_hold_cnt++;
 165
 166         trace_page_pool_state_hold(pool, page, pool->pages_state_hold_cnt);
 167
 168         /* When page just alloc'ed is should/must have refcnt 1. */
 169         return page;
 170 }
 171
 172 /* For using page_pool replace: alloc_pages() API calls, but provide
 173  * synchronization guarantee for allocation side.
 174  */
 175 struct page *page_pool_alloc_pages(struct page_pool *pool, gfp_t gfp)
 176 {
 177         struct page *page;
 178
 179         /* Fast-path: Get a page from cache */
 180         page = __page_pool_get_cached(pool);
 181         if (page)
 182                 return page;
 183
 184         /* Slow-path: cache empty, do real allocation */
 185         page = __page_pool_alloc_pages_slow(pool, gfp);
 186         return page;
 187 }
 188 EXPORT_SYMBOL(page_pool_alloc_pages);
 189
 190 /* Calculate distance between two u32 values, valid if distance is below 2^(31)
 191  *  https://en.wikipedia.org/wiki/Serial_number_arithmetic#General_Solution
 192  */
 193 #define _distance(a, b) (s32)((a) - (b))
 194
 195 static s32 page_pool_inflight(struct page_pool *pool)
 196 {
 197         u32 release_cnt = atomic_read(&pool->pages_state_release_cnt);
 198         u32 hold_cnt = READ_ONCE(pool->pages_state_hold_cnt);
 199         s32 distance;
 200
 201         distance = _distance(hold_cnt, release_cnt);
 202
 203         trace_page_pool_inflight(pool, distance, hold_cnt, release_cnt);
 204         return distance;
 205 }
 206
 207 static bool __page_pool_safe_to_destroy(struct page_pool *pool)
 208 {
 209         s32 inflight = page_pool_inflight(pool);
 210
 211         /* The distance should not be able to become negative */
 212         WARN(inflight < 0, "Negative(%d) inflight packet-pages", inflight);
 213
 214         return (inflight == 0);
 215 }
 216
 217 /* Cleanup page_pool state from page */
 218 static void __page_pool_clean_page(struct page_pool *pool,
 219                                    struct page *page)
 220 {
 221         dma_addr_t dma;
 222
 223         if (!(pool->p.flags & PP_FLAG_DMA_MAP))
 224                 goto skip_dma_unmap;
 225
 226         dma = page->dma_addr;
 227         /* DMA unmap */
 228         dma_unmap_page_attrs(pool->p.dev, dma,
 229                              PAGE_SIZE << pool->p.order, pool->p.dma_dir,
 230                              DMA_ATTR_SKIP_CPU_SYNC);
 231         page->dma_addr = 0;
 232 skip_dma_unmap:
 233         atomic_inc(&pool->pages_state_release_cnt);
 234         trace_page_pool_state_release(pool, page,
 235                               atomic_read(&pool->pages_state_release_cnt));
 236 }
 237
 238 /* unmap the page and clean our state */
 239 void page_pool_unmap_page(struct page_pool *pool, struct page *page)
 240 {
 241         /* When page is unmapped, this implies page will not be
 242          * returned to page_pool.
 243          */
 244         __page_pool_clean_page(pool, page);
 245 }
 246 EXPORT_SYMBOL(page_pool_unmap_page);
 247
 248 /* Return a page to the page allocator, cleaning up our state */
 249 static void __page_pool_return_page(struct page_pool *pool, struct page *page)
 250 {
 251         __page_pool_clean_page(pool, page);
 252
 253         put_page(page);
 254         /* An optimization would be to call __free_pages(page, pool->p.order)
 255          * knowing page is not part of page-cache (thus avoiding a
 256          * __page_cache_release() call).
 257          */
 258 }
 259
 260 static bool __page_pool_recycle_into_ring(struct page_pool *pool,
 261                                    struct page *page)
 262 {
 263         int ret;
 264         /* BH protection not needed if current is serving softirq */
 265         if (in_serving_softirq())
 266                 ret = ptr_ring_produce(&pool->ring, page);
 267         else
 268                 ret = ptr_ring_produce_bh(&pool->ring, page);
 269
 270         return (ret == 0) ? true : false;
 271 }
 272
 273 /* Only allow direct recycling in special circumstances, into the
 274  * alloc side cache.  E.g. during RX-NAPI processing for XDP_DROP use-case.
 275  *
 276  * Caller must provide appropriate safe context.
 277  */
 278 static bool __page_pool_recycle_direct(struct page *page,
 279                                        struct page_pool *pool)
 280 {
 281         if (unlikely(pool->alloc.count == PP_ALLOC_CACHE_SIZE))
 282                 return false;
 283
 284         /* Caller MUST have verified/know (page_ref_count(page) == 1) */
 285         pool->alloc.cache[pool->alloc.count++] = page;
 286         return true;
 287 }
 288
 289 void __page_pool_put_page(struct page_pool *pool,
 290                           struct page *page, bool allow_direct)
 291 {
 292         /* This allocator is optimized for the XDP mode that uses
 293          * one-frame-per-page, but have fallbacks that act like the
 294          * regular page allocator APIs.
 295          *
 296          * refcnt == 1 means page_pool owns page, and can recycle it.
 297          */
 298         if (likely(page_ref_count(page) == 1)) {
 299                 /* Read barrier done in page_ref_count / READ_ONCE */
 300
 301                 if (allow_direct && in_serving_softirq())
 302                         if (__page_pool_recycle_direct(page, pool))
 303                                 return;
 304
 305                 if (!__page_pool_recycle_into_ring(pool, page)) {
 306                         /* Cache full, fallback to free pages */
 307                         __page_pool_return_page(pool, page);
 308                 }
 309                 return;
 310         }
 311         /* Fallback/non-XDP mode: API user have elevated refcnt.
 312          *
 313          * Many drivers split up the page into fragments, and some
 314          * want to keep doing this to save memory and do refcnt based
 315          * recycling. Support this use case too, to ease drivers
 316          * switching between XDP/non-XDP.
 317          *
 318          * In-case page_pool maintains the DMA mapping, API user must
 319          * call page_pool_put_page once.  In this elevated refcnt
 320          * case, the DMA is unmapped/released, as driver is likely
 321          * doing refcnt based recycle tricks, meaning another process
 322          * will be invoking put_page.
 323          */
 324         __page_pool_clean_page(pool, page);
 325         put_page(page);
 326 }
 327 EXPORT_SYMBOL(__page_pool_put_page);
 328
 329 static void __page_pool_empty_ring(struct page_pool *pool)
 330 {
 331         struct page *page;
 332
 333         /* Empty recycle ring */
 334         while ((page = ptr_ring_consume_bh(&pool->ring))) {
 335                 /* Verify the refcnt invariant of cached pages */
 336                 if (!(page_ref_count(page) == 1))
 337                         pr_crit("%s() page_pool refcnt %d violation\n",
 338                                 __func__, page_ref_count(page));
 339
 340                 __page_pool_return_page(pool, page);
 341         }
 342 }
 343
 344 static void __warn_in_flight(struct page_pool *pool)
 345 {
 346         u32 release_cnt = atomic_read(&pool->pages_state_release_cnt);
 347         u32 hold_cnt = READ_ONCE(pool->pages_state_hold_cnt);
 348         s32 distance;
 349
 350         distance = _distance(hold_cnt, release_cnt);
 351
 352         /* Drivers should fix this, but only problematic when DMA is used */
 353         WARN(1, "Still in-flight pages:%d hold:%u released:%u",
 354              distance, hold_cnt, release_cnt);
 355 }
 356
 357 void __page_pool_free(struct page_pool *pool)
 358 {
 359         WARN(pool->alloc.count, "API usage violation");
 360         WARN(!ptr_ring_empty(&pool->ring), "ptr_ring is not empty");
 361
 362         /* Can happen due to forced shutdown */
 363         if (!__page_pool_safe_to_destroy(pool))
 364                 __warn_in_flight(pool);
 365
 366         ptr_ring_cleanup(&pool->ring, NULL);
 367
 368         if (pool->p.flags & PP_FLAG_DMA_MAP)
 369                 put_device(pool->p.dev);
 370
 371         kfree(pool);
 372 }
 373 EXPORT_SYMBOL(__page_pool_free);
 374
 375 /* Request to shutdown: release pages cached by page_pool, and check
 376  * for in-flight pages
 377  */
 378 bool __page_pool_request_shutdown(struct page_pool *pool)
 379 {
 380         struct page *page;
 381
 382         /* Empty alloc cache, assume caller made sure this is
 383          * no-longer in use, and page_pool_alloc_pages() cannot be
 384          * call concurrently.
 385          */
 386         while (pool->alloc.count) {
 387                 page = pool->alloc.cache[--pool->alloc.count];
 388                 __page_pool_return_page(pool, page);
 389         }
 390
 391         /* No more consumers should exist, but producers could still
 392          * be in-flight.
 393          */
 394         __page_pool_empty_ring(pool);
 395
 396         return __page_pool_safe_to_destroy(pool);
 397 }
 398 EXPORT_SYMBOL(__page_pool_request_shutdown);