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 <net/page_pool/types.h>
56
57#ifdef CONFIG_PAGE_POOL_STATS
58/* Deprecated driver-facing API, use netlink instead */
59int page_pool_ethtool_stats_get_count(void);
60u8 *page_pool_ethtool_stats_get_strings(u8 *data);
61u64 *page_pool_ethtool_stats_get(u64 *data, void *stats);
62
63bool page_pool_get_stats(const struct page_pool *pool,
64 struct page_pool_stats *stats);
65#else
66static inline int page_pool_ethtool_stats_get_count(void)
67{
68 return 0;
69}
70
71static inline u8 *page_pool_ethtool_stats_get_strings(u8 *data)
72{
73 return data;
74}
75
76static inline u64 *page_pool_ethtool_stats_get(u64 *data, void *stats)
77{
78 return data;
79}
80#endif
81
82/**
83 * page_pool_dev_alloc_pages() - allocate a page.
84 * @pool: pool from which to allocate
85 *
86 * Get a page from the page allocator or page_pool caches.
87 */
88static inline struct page *page_pool_dev_alloc_pages(struct page_pool *pool)
89{
90 gfp_t gfp = (GFP_ATOMIC | __GFP_NOWARN);
91
92 return page_pool_alloc_pages(pool, gfp);
93}
94
95/**
96 * page_pool_dev_alloc_frag() - allocate a page fragment.
97 * @pool: pool from which to allocate
98 * @offset: offset to the allocated page
99 * @size: requested size
100 *
101 * Get a page fragment from the page allocator or page_pool caches.
102 *
103 * Return:
104 * Return allocated page fragment, otherwise return NULL.
105 */
106static inline struct page *page_pool_dev_alloc_frag(struct page_pool *pool,
107 unsigned int *offset,
108 unsigned int size)
109{
110 gfp_t gfp = (GFP_ATOMIC | __GFP_NOWARN);
111
112 return page_pool_alloc_frag(pool, offset, size, gfp);
113}
114
115static inline struct page *page_pool_alloc(struct page_pool *pool,
116 unsigned int *offset,
117 unsigned int *size, gfp_t gfp)
118{
119 unsigned int max_size = PAGE_SIZE << pool->p.order;
120 struct page *page;
121
122 if ((*size << 1) > max_size) {
123 *size = max_size;
124 *offset = 0;
125 return page_pool_alloc_pages(pool, gfp);
126 }
127
128 page = page_pool_alloc_frag(pool, offset, size: *size, gfp);
129 if (unlikely(!page))
130 return NULL;
131
132 /* There is very likely not enough space for another fragment, so append
133 * the remaining size to the current fragment to avoid truesize
134 * underestimate problem.
135 */
136 if (pool->frag_offset + *size > max_size) {
137 *size = max_size - *offset;
138 pool->frag_offset = max_size;
139 }
140
141 return page;
142}
143
144/**
145 * page_pool_dev_alloc() - allocate a page or a page fragment.
146 * @pool: pool from which to allocate
147 * @offset: offset to the allocated page
148 * @size: in as the requested size, out as the allocated size
149 *
150 * Get a page or a page fragment from the page allocator or page_pool caches
151 * depending on the requested size in order to allocate memory with least memory
152 * utilization and performance penalty.
153 *
154 * Return:
155 * Return allocated page or page fragment, otherwise return NULL.
156 */
157static inline struct page *page_pool_dev_alloc(struct page_pool *pool,
158 unsigned int *offset,
159 unsigned int *size)
160{
161 gfp_t gfp = (GFP_ATOMIC | __GFP_NOWARN);
162
163 return page_pool_alloc(pool, offset, size, gfp);
164}
165
166static inline void *page_pool_alloc_va(struct page_pool *pool,
167 unsigned int *size, gfp_t gfp)
168{
169 unsigned int offset;
170 struct page *page;
171
172 /* Mask off __GFP_HIGHMEM to ensure we can use page_address() */
173 page = page_pool_alloc(pool, offset: &offset, size, gfp: gfp & ~__GFP_HIGHMEM);
174 if (unlikely(!page))
175 return NULL;
176
177 return page_address(page) + offset;
178}
179
180/**
181 * page_pool_dev_alloc_va() - allocate a page or a page fragment and return its
182 * va.
183 * @pool: pool from which to allocate
184 * @size: in as the requested size, out as the allocated size
185 *
186 * This is just a thin wrapper around the page_pool_alloc() API, and
187 * it returns va of the allocated page or page fragment.
188 *
189 * Return:
190 * Return the va for the allocated page or page fragment, otherwise return NULL.
191 */
192static inline void *page_pool_dev_alloc_va(struct page_pool *pool,
193 unsigned int *size)
194{
195 gfp_t gfp = (GFP_ATOMIC | __GFP_NOWARN);
196
197 return page_pool_alloc_va(pool, size, gfp);
198}
199
200/**
201 * page_pool_get_dma_dir() - Retrieve the stored DMA direction.
202 * @pool: pool from which page was allocated
203 *
204 * Get the stored dma direction. A driver might decide to store this locally
205 * and avoid the extra cache line from page_pool to determine the direction.
206 */
207static
208inline enum dma_data_direction page_pool_get_dma_dir(struct page_pool *pool)
209{
210 return pool->p.dma_dir;
211}
212
213/**
214 * page_pool_fragment_page() - split a fresh page into fragments
215 * @page: page to split
216 * @nr: references to set
217 *
218 * pp_ref_count represents the number of outstanding references to the page,
219 * which will be freed using page_pool APIs (rather than page allocator APIs
220 * like put_page()). Such references are usually held by page_pool-aware
221 * objects like skbs marked for page pool recycling.
222 *
223 * This helper allows the caller to take (set) multiple references to a
224 * freshly allocated page. The page must be freshly allocated (have a
225 * pp_ref_count of 1). This is commonly done by drivers and
226 * "fragment allocators" to save atomic operations - either when they know
227 * upfront how many references they will need; or to take MAX references and
228 * return the unused ones with a single atomic dec(), instead of performing
229 * multiple atomic inc() operations.
230 */
231static inline void page_pool_fragment_page(struct page *page, long nr)
232{
233 atomic_long_set(v: &page->pp_ref_count, i: nr);
234}
235
236static inline long page_pool_unref_page(struct page *page, long nr)
237{
238 long ret;
239
240 /* If nr == pp_ref_count then we have cleared all remaining
241 * references to the page:
242 * 1. 'n == 1': no need to actually overwrite it.
243 * 2. 'n != 1': overwrite it with one, which is the rare case
244 * for pp_ref_count draining.
245 *
246 * The main advantage to doing this is that not only we avoid a atomic
247 * update, as an atomic_read is generally a much cheaper operation than
248 * an atomic update, especially when dealing with a page that may be
249 * referenced by only 2 or 3 users; but also unify the pp_ref_count
250 * handling by ensuring all pages have partitioned into only 1 piece
251 * initially, and only overwrite it when the page is partitioned into
252 * more than one piece.
253 */
254 if (atomic_long_read(v: &page->pp_ref_count) == nr) {
255 /* As we have ensured nr is always one for constant case using
256 * the BUILD_BUG_ON(), only need to handle the non-constant case
257 * here for pp_ref_count draining, which is a rare case.
258 */
259 BUILD_BUG_ON(__builtin_constant_p(nr) && nr != 1);
260 if (!__builtin_constant_p(nr))
261 atomic_long_set(v: &page->pp_ref_count, i: 1);
262
263 return 0;
264 }
265
266 ret = atomic_long_sub_return(i: nr, v: &page->pp_ref_count);
267 WARN_ON(ret < 0);
268
269 /* We are the last user here too, reset pp_ref_count back to 1 to
270 * ensure all pages have been partitioned into 1 piece initially,
271 * this should be the rare case when the last two fragment users call
272 * page_pool_unref_page() currently.
273 */
274 if (unlikely(!ret))
275 atomic_long_set(v: &page->pp_ref_count, i: 1);
276
277 return ret;
278}
279
280static inline void page_pool_ref_page(struct page *page)
281{
282 atomic_long_inc(v: &page->pp_ref_count);
283}
284
285static inline bool page_pool_is_last_ref(struct page *page)
286{
287 /* If page_pool_unref_page() returns 0, we were the last user */
288 return page_pool_unref_page(page, nr: 1) == 0;
289}
290
291/**
292 * page_pool_put_page() - release a reference to a page pool page
293 * @pool: pool from which page was allocated
294 * @page: page to release a reference on
295 * @dma_sync_size: how much of the page may have been touched by the device
296 * @allow_direct: released by the consumer, allow lockless caching
297 *
298 * The outcome of this depends on the page refcnt. If the driver bumps
299 * the refcnt > 1 this will unmap the page. If the page refcnt is 1
300 * the allocator owns the page and will try to recycle it in one of the pool
301 * caches. If PP_FLAG_DMA_SYNC_DEV is set, the page will be synced for_device
302 * using dma_sync_single_range_for_device().
303 */
304static inline void page_pool_put_page(struct page_pool *pool,
305 struct page *page,
306 unsigned int dma_sync_size,
307 bool allow_direct)
308{
309 /* When page_pool isn't compiled-in, net/core/xdp.c doesn't
310 * allow registering MEM_TYPE_PAGE_POOL, but shield linker.
311 */
312#ifdef CONFIG_PAGE_POOL
313 if (!page_pool_is_last_ref(page))
314 return;
315
316 page_pool_put_unrefed_page(pool, page, dma_sync_size, allow_direct);
317#endif
318}
319
320/**
321 * page_pool_put_full_page() - release a reference on a page pool page
322 * @pool: pool from which page was allocated
323 * @page: page to release a reference on
324 * @allow_direct: released by the consumer, allow lockless caching
325 *
326 * Similar to page_pool_put_page(), but will DMA sync the entire memory area
327 * as configured in &page_pool_params.max_len.
328 */
329static inline void page_pool_put_full_page(struct page_pool *pool,
330 struct page *page, bool allow_direct)
331{
332 page_pool_put_page(pool, page, dma_sync_size: -1, allow_direct);
333}
334
335/**
336 * page_pool_recycle_direct() - release a reference on a page pool page
337 * @pool: pool from which page was allocated
338 * @page: page to release a reference on
339 *
340 * Similar to page_pool_put_full_page() but caller must guarantee safe context
341 * (e.g NAPI), since it will recycle the page directly into the pool fast cache.
342 */
343static inline void page_pool_recycle_direct(struct page_pool *pool,
344 struct page *page)
345{
346 page_pool_put_full_page(pool, page, allow_direct: true);
347}
348
349#define PAGE_POOL_32BIT_ARCH_WITH_64BIT_DMA \
350 (sizeof(dma_addr_t) > sizeof(unsigned long))
351
352/**
353 * page_pool_free_va() - free a va into the page_pool
354 * @pool: pool from which va was allocated
355 * @va: va to be freed
356 * @allow_direct: freed by the consumer, allow lockless caching
357 *
358 * Free a va allocated from page_pool_allo_va().
359 */
360static inline void page_pool_free_va(struct page_pool *pool, void *va,
361 bool allow_direct)
362{
363 page_pool_put_page(pool, page: virt_to_head_page(x: va), dma_sync_size: -1, allow_direct);
364}
365
366/**
367 * page_pool_get_dma_addr() - Retrieve the stored DMA address.
368 * @page: page allocated from a page pool
369 *
370 * Fetch the DMA address of the page. The page pool to which the page belongs
371 * must had been created with PP_FLAG_DMA_MAP.
372 */
373static inline dma_addr_t page_pool_get_dma_addr(struct page *page)
374{
375 dma_addr_t ret = page->dma_addr;
376
377 if (PAGE_POOL_32BIT_ARCH_WITH_64BIT_DMA)
378 ret <<= PAGE_SHIFT;
379
380 return ret;
381}
382
383static inline bool page_pool_set_dma_addr(struct page *page, dma_addr_t addr)
384{
385 if (PAGE_POOL_32BIT_ARCH_WITH_64BIT_DMA) {
386 page->dma_addr = addr >> PAGE_SHIFT;
387
388 /* We assume page alignment to shave off bottom bits,
389 * if this "compression" doesn't work we need to drop.
390 */
391 return addr != (dma_addr_t)page->dma_addr << PAGE_SHIFT;
392 }
393
394 page->dma_addr = addr;
395 return false;
396}
397
398static inline bool page_pool_put(struct page_pool *pool)
399{
400 return refcount_dec_and_test(r: &pool->user_cnt);
401}
402
403static inline void page_pool_nid_changed(struct page_pool *pool, int new_nid)
404{
405 if (unlikely(pool->p.nid != new_nid))
406 page_pool_update_nid(pool, new_nid);
407}
408
409#endif /* _NET_PAGE_POOL_HELPERS_H */
410

source code of linux/include/net/page_pool/helpers.h