1 /* SPDX-License-Identifier: GPL-2.0
2 *
3 * page_pool/helpers.h
4 * Author: Jesper Dangaard Brouer <netoptimizer@brouer.com>
5 * Copyright (C) 2016 Red Hat, Inc.
6 */
7
8 /**
9 * DOC: page_pool allocator
10 *
11 * The page_pool allocator is optimized for recycling page or page fragment used
12 * by skb packet and xdp frame.
13 *
14 * Basic use involves replacing any alloc_pages() calls with page_pool_alloc(),
15 * which allocate memory with or without page splitting depending on the
16 * requested memory size.
17 *
18 * If the driver knows that it always requires full pages or its allocations are
19 * always smaller than half a page, it can use one of the more specific API
20 * calls:
21 *
22 * 1. page_pool_alloc_pages(): allocate memory without page splitting when
23 * driver knows that the memory it need is always bigger than half of the page
24 * allocated from page pool. There is no cache line dirtying for 'struct page'
25 * when a page is recycled back to the page pool.
26 *
27 * 2. page_pool_alloc_frag(): allocate memory with page splitting when driver
28 * knows that the memory it need is always smaller than or equal to half of the
29 * page allocated from page pool. Page splitting enables memory saving and thus
30 * avoids TLB/cache miss for data access, but there also is some cost to
31 * implement page splitting, mainly some cache line dirtying/bouncing for
32 * 'struct page' and atomic operation for page->pp_ref_count.
33 *
34 * The API keeps track of in-flight pages, in order to let API users know when
35 * it is safe to free a page_pool object, the API users must call
36 * page_pool_put_page() or page_pool_free_va() to free the page_pool object, or
37 * attach the page_pool object to a page_pool-aware object like skbs marked with
38 * skb_mark_for_recycle().
39 *
40 * page_pool_put_page() may be called multiple times on the same page if a page
41 * is split into multiple fragments. For the last fragment, it will either
42 * recycle the page, or in case of page->_refcount > 1, it will release the DMA
43 * mapping and in-flight state accounting.
44 *
45 * dma_sync_single_range_for_device() is only called for the last fragment when
46 * page_pool is created with PP_FLAG_DMA_SYNC_DEV flag, so it depends on the
47 * last freed fragment to do the sync_for_device operation for all fragments in
48 * the same page when a page is split. The API user must setup pool->p.max_len
49 * and pool->p.offset correctly and ensure that page_pool_put_page() is called
50 * with dma_sync_size being -1 for fragment API.
51 */
52 #ifndef _NET_PAGE_POOL_HELPERS_H
53 #define _NET_PAGE_POOL_HELPERS_H
54
55 #include <linux/dma-mapping.h>
56
57 #include <net/page_pool/types.h>
58 #include <net/net_debug.h>
59 #include <net/netmem.h>
60
61 #ifdef CONFIG_PAGE_POOL_STATS
62 /* Deprecated driver-facing API, use netlink instead */
63 int page_pool_ethtool_stats_get_count(void);
64 u8 *page_pool_ethtool_stats_get_strings(u8 *data);
65 u64 *page_pool_ethtool_stats_get(u64 *data, const void *stats);
66
67 bool page_pool_get_stats(const struct page_pool *pool,
68 struct page_pool_stats *stats);
69 #else
70 static inline int page_pool_ethtool_stats_get_count(void)
71 {
72 return 0;
73 }
74
75 static inline u8 *page_pool_ethtool_stats_get_strings(u8 *data)
76 {
77 return data;
78 }
79
80 static inline u64 *page_pool_ethtool_stats_get(u64 *data, const void *stats)
81 {
82 return data;
83 }
84 #endif
85
86 /**
87 * page_pool_dev_alloc_pages() - allocate a page.
88 * @pool: pool from which to allocate
89 *
90 * Get a page from the page allocator or page_pool caches.
91 */
92 static inline struct page *page_pool_dev_alloc_pages(struct page_pool *pool)
93 {
94 gfp_t gfp = (GFP_ATOMIC | __GFP_NOWARN);
95
96 return page_pool_alloc_pages(pool, gfp);
97 }
98
99 /**
100 * page_pool_dev_alloc_frag() - allocate a page fragment.
101 * @pool: pool from which to allocate
102 * @offset: offset to the allocated page
103 * @size: requested size
104 *
105 * Get a page fragment from the page allocator or page_pool caches.
106 *
107 * Return:
108 * Return allocated page fragment, otherwise return NULL.
109 */
110 static inline struct page *page_pool_dev_alloc_frag(struct page_pool *pool,
111 unsigned int *offset,
112 unsigned int size)
113 {
114 gfp_t gfp = (GFP_ATOMIC | __GFP_NOWARN);
115
116 return page_pool_alloc_frag(pool, offset, size, gfp);
117 }
118
119 static inline struct page *page_pool_alloc(struct page_pool *pool,
120 unsigned int *offset,
121 unsigned int *size, gfp_t gfp)
122 {
123 unsigned int max_size = PAGE_SIZE << pool->p.order;
124 struct page *page;
125
126 if ((*size << 1) > max_size) {
127 *size = max_size;
128 *offset = 0;
129 return page_pool_alloc_pages(pool, gfp);
130 }
131
132 page = page_pool_alloc_frag(pool, offset, *size, gfp);
133 if (unlikely(!page))
134 return NULL;
135
136 /* There is very likely not enough space for another fragment, so append
137 * the remaining size to the current fragment to avoid truesize
138 * underestimate problem.
139 */
140 if (pool->frag_offset + *size > max_size) {
141 *size = max_size - *offset;
142 pool->frag_offset = max_size;
143 }
144
145 return page;
146 }
147
148 /**
149 * page_pool_dev_alloc() - allocate a page or a page fragment.
150 * @pool: pool from which to allocate
151 * @offset: offset to the allocated page
152 * @size: in as the requested size, out as the allocated size
153 *
154 * Get a page or a page fragment from the page allocator or page_pool caches
155 * depending on the requested size in order to allocate memory with least memory
156 * utilization and performance penalty.
157 *
158 * Return:
159 * Return allocated page or page fragment, otherwise return NULL.
160 */
161 static inline struct page *page_pool_dev_alloc(struct page_pool *pool,
162 unsigned int *offset,
163 unsigned int *size)
164 {
165 gfp_t gfp = (GFP_ATOMIC | __GFP_NOWARN);
166
167 return page_pool_alloc(pool, offset, size, gfp);
168 }
169
170 static inline void *page_pool_alloc_va(struct page_pool *pool,
171 unsigned int *size, gfp_t gfp)
172 {
173 unsigned int offset;
174 struct page *page;
175
176 /* Mask off __GFP_HIGHMEM to ensure we can use page_address() */
177 page = page_pool_alloc(pool, &offset, size, gfp & ~__GFP_HIGHMEM);
178 if (unlikely(!page))
179 return NULL;
180
181 return page_address(page) + offset;
182 }
183
184 /**
185 * page_pool_dev_alloc_va() - allocate a page or a page fragment and return its
186 * va.
187 * @pool: pool from which to allocate
188 * @size: in as the requested size, out as the allocated size
189 *
190 * This is just a thin wrapper around the page_pool_alloc() API, and
191 * it returns va of the allocated page or page fragment.
192 *
193 * Return:
194 * Return the va for the allocated page or page fragment, otherwise return NULL.
195 */
196 static inline void *page_pool_dev_alloc_va(struct page_pool *pool,
197 unsigned int *size)
198 {
199 gfp_t gfp = (GFP_ATOMIC | __GFP_NOWARN);
200
201 return page_pool_alloc_va(pool, size, gfp);
202 }
203
204 /**
205 * page_pool_get_dma_dir() - Retrieve the stored DMA direction.
206 * @pool: pool from which page was allocated
207 *
208 * Get the stored dma direction. A driver might decide to store this locally
209 * and avoid the extra cache line from page_pool to determine the direction.
210 */
211 static inline enum dma_data_direction
212 page_pool_get_dma_dir(const struct page_pool *pool)
213 {
214 return pool->p.dma_dir;
215 }
216
217 static inline void page_pool_fragment_netmem(netmem_ref netmem, long nr)
218 {
219 atomic_long_set(&netmem_to_page(netmem)->pp_ref_count, nr);
220 }
221
222 /**
223 * page_pool_fragment_page() - split a fresh page into fragments
224 * @page: page to split
225 * @nr: references to set
226 *
227 * pp_ref_count represents the number of outstanding references to the page,
228 * which will be freed using page_pool APIs (rather than page allocator APIs
229 * like put_page()). Such references are usually held by page_pool-aware
230 * objects like skbs marked for page pool recycling.
231 *
232 * This helper allows the caller to take (set) multiple references to a
233 * freshly allocated page. The page must be freshly allocated (have a
234 * pp_ref_count of 1). This is commonly done by drivers and
235 * "fragment allocators" to save atomic operations - either when they know
236 * upfront how many references they will need; or to take MAX references and
237 * return the unused ones with a single atomic dec(), instead of performing
238 * multiple atomic inc() operations.
239 */
240 static inline void page_pool_fragment_page(struct page *page, long nr)
241 {
242 page_pool_fragment_netmem(page_to_netmem(page), nr);
243 }
244
245 static inline long page_pool_unref_netmem(netmem_ref netmem, long nr)
246 {
247 struct page *page = netmem_to_page(netmem);
248 long ret;
249
250 /* If nr == pp_ref_count then we have cleared all remaining
251 * references to the page:
252 * 1. 'n == 1': no need to actually overwrite it.
253 * 2. 'n != 1': overwrite it with one, which is the rare case
254 * for pp_ref_count draining.
255 *
256 * The main advantage to doing this is that not only we avoid a atomic
257 * update, as an atomic_read is generally a much cheaper operation than
258 * an atomic update, especially when dealing with a page that may be
259 * referenced by only 2 or 3 users; but also unify the pp_ref_count
260 * handling by ensuring all pages have partitioned into only 1 piece
261 * initially, and only overwrite it when the page is partitioned into
262 * more than one piece.
263 */
264 if (atomic_long_read(&page->pp_ref_count) == nr) {
265 /* As we have ensured nr is always one for constant case using
266 * the BUILD_BUG_ON(), only need to handle the non-constant case
267 * here for pp_ref_count draining, which is a rare case.
268 */
269 BUILD_BUG_ON(__builtin_constant_p(nr) && nr != 1);
270 if (!__builtin_constant_p(nr))
271 atomic_long_set(&page->pp_ref_count, 1);
272
273 return 0;
274 }
275
276 ret = atomic_long_sub_return(nr, &page->pp_ref_count);
277 WARN_ON(ret < 0);
278
279 /* We are the last user here too, reset pp_ref_count back to 1 to
280 * ensure all pages have been partitioned into 1 piece initially,
281 * this should be the rare case when the last two fragment users call
282 * page_pool_unref_page() currently.
283 */
284 if (unlikely(!ret))
285 atomic_long_set(&page->pp_ref_count, 1);
286
287 return ret;
288 }
289
290 static inline long page_pool_unref_page(struct page *page, long nr)
291 {
292 return page_pool_unref_netmem(page_to_netmem(page), nr);
293 }
294
295 static inline void page_pool_ref_netmem(netmem_ref netmem)
296 {
297 atomic_long_inc(&netmem_to_page(netmem)->pp_ref_count);
298 }
299
300 static inline void page_pool_ref_page(struct page *page)
301 {
302 page_pool_ref_netmem(page_to_netmem(page));
303 }
304
305 static inline bool page_pool_is_last_ref(netmem_ref netmem)
306 {
307 /* If page_pool_unref_page() returns 0, we were the last user */
308 return page_pool_unref_netmem(netmem, 1) == 0;
309 }
310
311 static inline void page_pool_put_netmem(struct page_pool *pool,
312 netmem_ref netmem,
313 unsigned int dma_sync_size,
314 bool allow_direct)
315 {
316 /* When page_pool isn't compiled-in, net/core/xdp.c doesn't
317 * allow registering MEM_TYPE_PAGE_POOL, but shield linker.
318 */
319 #ifdef CONFIG_PAGE_POOL
320 if (!page_pool_is_last_ref(netmem))
321 return;
322
323 page_pool_put_unrefed_netmem(pool, netmem, dma_sync_size, allow_direct);
324 #endif
325 }
326
327 /**
328 * page_pool_put_page() - release a reference to a page pool page
329 * @pool: pool from which page was allocated
330 * @page: page to release a reference on
331 * @dma_sync_size: how much of the page may have been touched by the device
332 * @allow_direct: released by the consumer, allow lockless caching
333 *
334 * The outcome of this depends on the page refcnt. If the driver bumps
335 * the refcnt > 1 this will unmap the page. If the page refcnt is 1
336 * the allocator owns the page and will try to recycle it in one of the pool
337 * caches. If PP_FLAG_DMA_SYNC_DEV is set, the page will be synced for_device
338 * using dma_sync_single_range_for_device().
339 */
340 static inline void page_pool_put_page(struct page_pool *pool,
341 struct page *page,
342 unsigned int dma_sync_size,
343 bool allow_direct)
344 {
345 page_pool_put_netmem(pool, page_to_netmem(page), dma_sync_size,
346 allow_direct);
347 }
348
349 static inline void page_pool_put_full_netmem(struct page_pool *pool,
350 netmem_ref netmem,
351 bool allow_direct)
352 {
353 page_pool_put_netmem(pool, netmem, -1, allow_direct);
354 }
355
356 /**
357 * page_pool_put_full_page() - release a reference on a page pool page
358 * @pool: pool from which page was allocated
359 * @page: page to release a reference on
360 * @allow_direct: released by the consumer, allow lockless caching
361 *
362 * Similar to page_pool_put_page(), but will DMA sync the entire memory area
363 * as configured in &page_pool_params.max_len.
364 */
365 static inline void page_pool_put_full_page(struct page_pool *pool,
366 struct page *page, bool allow_direct)
367 {
368 page_pool_put_netmem(pool, page_to_netmem(page), -1, allow_direct);
369 }
370
371 /**
372 * page_pool_recycle_direct() - release a reference on a page pool page
373 * @pool: pool from which page was allocated
374 * @page: page to release a reference on
375 *
376 * Similar to page_pool_put_full_page() but caller must guarantee safe context
377 * (e.g NAPI), since it will recycle the page directly into the pool fast cache.
378 */
379 static inline void page_pool_recycle_direct(struct page_pool *pool,
380 struct page *page)
381 {
382 page_pool_put_full_page(pool, page, true);
383 }
384
385 #define PAGE_POOL_32BIT_ARCH_WITH_64BIT_DMA \
386 (sizeof(dma_addr_t) > sizeof(unsigned long))
387
388 /**
389 * page_pool_free_va() - free a va into the page_pool
390 * @pool: pool from which va was allocated
391 * @va: va to be freed
392 * @allow_direct: freed by the consumer, allow lockless caching
393 *
394 * Free a va allocated from page_pool_allo_va().
395 */
396 static inline void page_pool_free_va(struct page_pool *pool, void *va,
397 bool allow_direct)
398 {
399 page_pool_put_page(pool, virt_to_head_page(va), -1, allow_direct);
400 }
401
402 static inline dma_addr_t page_pool_get_dma_addr_netmem(netmem_ref netmem)
403 {
404 struct page *page = netmem_to_page(netmem);
405
406 dma_addr_t ret = page->dma_addr;
407
408 if (PAGE_POOL_32BIT_ARCH_WITH_64BIT_DMA)
409 ret <<= PAGE_SHIFT;
410
411 return ret;
412 }
413
414 /**
415 * page_pool_get_dma_addr() - Retrieve the stored DMA address.
416 * @page: page allocated from a page pool
417 *
418 * Fetch the DMA address of the page. The page pool to which the page belongs
419 * must had been created with PP_FLAG_DMA_MAP.
420 */
421 static inline dma_addr_t page_pool_get_dma_addr(const struct page *page)
422 {
423 return page_pool_get_dma_addr_netmem(page_to_netmem((struct page *)page));
424 }
425
426 static inline bool page_pool_set_dma_addr_netmem(netmem_ref netmem,
427 dma_addr_t addr)
428 {
429 struct page *page = netmem_to_page(netmem);
430
431 if (PAGE_POOL_32BIT_ARCH_WITH_64BIT_DMA) {
432 page->dma_addr = addr >> PAGE_SHIFT;
433
434 /* We assume page alignment to shave off bottom bits,
435 * if this "compression" doesn't work we need to drop.
436 */
437 return addr != (dma_addr_t)page->dma_addr << PAGE_SHIFT;
438 }
439
440 page->dma_addr = addr;
441 return false;
442 }
443
444 /**
445 * page_pool_dma_sync_for_cpu - sync Rx page for CPU after it's written by HW
446 * @pool: &page_pool the @page belongs to
447 * @page: page to sync
448 * @offset: offset from page start to "hard" start if using PP frags
449 * @dma_sync_size: size of the data written to the page
450 *
451 * Can be used as a shorthand to sync Rx pages before accessing them in the
452 * driver. Caller must ensure the pool was created with ``PP_FLAG_DMA_MAP``.
453 * Note that this version performs DMA sync unconditionally, even if the
454 * associated PP doesn't perform sync-for-device.
455 */
456 static inline void page_pool_dma_sync_for_cpu(const struct page_pool *pool,
457 const struct page *page,
458 u32 offset, u32 dma_sync_size)
459 {
460 dma_sync_single_range_for_cpu(pool->p.dev,
461 page_pool_get_dma_addr(page),
462 offset + pool->p.offset, dma_sync_size,
463 page_pool_get_dma_dir(pool));
464 }
465
466 static inline bool page_pool_set_dma_addr(struct page *page, dma_addr_t addr)
467 {
468 return page_pool_set_dma_addr_netmem(page_to_netmem(page), addr);
469 }
470
471 static inline bool page_pool_put(struct page_pool *pool)
472 {
473 return refcount_dec_and_test(&pool->user_cnt);
474 }
475
476 static inline void page_pool_nid_changed(struct page_pool *pool, int new_nid)
477 {
478 if (unlikely(pool->p.nid != new_nid))
479 page_pool_update_nid(pool, new_nid);
480 }
481
482 #endif /* _NET_PAGE_POOL_HELPERS_H */
483
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