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