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); 400