1 /* SPDX-License-Identifier: GPL-2.0
4 * Author: Jesper Dangaard Brouer <netoptimizer@brouer.com>
5 * Copyright (C) 2016 Red Hat, Inc.
8 #include <linux/types.h>
9 #include <linux/kernel.h>
10 #include <linux/slab.h>
11 #include <linux/device.h>
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() */
19 #include <trace/events/page_pool.h>
21 static int page_pool_init(struct page_pool *pool,
22 const struct page_pool_params *params)
24 unsigned int ring_qsize = 1024; /* Default */
26 memcpy(&pool->p, params, sizeof(pool->p));
28 /* Validate only known flags were used */
29 if (pool->p.flags & ~(PP_FLAG_ALL))
32 if (pool->p.pool_size)
33 ring_qsize = pool->p.pool_size;
35 /* Sanity limit mem that can be pinned down */
36 if (ring_qsize > 32768)
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.
43 if ((pool->p.dma_dir != DMA_FROM_DEVICE) &&
44 (pool->p.dma_dir != DMA_BIDIRECTIONAL))
47 if (ptr_ring_init(&pool->ring, ring_qsize, GFP_KERNEL) < 0)
50 atomic_set(&pool->pages_state_release_cnt, 0);
52 /* Driver calling page_pool_create() also call page_pool_destroy() */
53 refcount_set(&pool->user_cnt, 1);
55 if (pool->p.flags & PP_FLAG_DMA_MAP)
56 get_device(pool->p.dev);
61 struct page_pool *page_pool_create(const struct page_pool_params *params)
63 struct page_pool *pool;
66 pool = kzalloc_node(sizeof(*pool), GFP_KERNEL, params->nid);
68 return ERR_PTR(-ENOMEM);
70 err = page_pool_init(pool, params);
72 pr_warn("%s() gave up with errno %d\n", __func__, err);
79 EXPORT_SYMBOL(page_pool_create);
82 static struct page *__page_pool_get_cached(struct page_pool *pool)
84 struct ptr_ring *r = &pool->ring;
88 /* Test for safe-context, caller should provide this guarantee */
89 if (likely(in_serving_softirq())) {
90 if (likely(pool->alloc.count)) {
92 page = pool->alloc.cache[--pool->alloc.count];
98 /* Quicker fallback, avoid locks when ring is empty */
99 if (__ptr_ring_empty(r))
102 /* Slow-path: Get page from locked ring queue,
103 * refill alloc array if requested.
105 spin_lock(&r->consumer_lock);
106 page = __ptr_ring_consume(r);
108 pool->alloc.count = __ptr_ring_consume_batched(r,
110 PP_ALLOC_CACHE_REFILL);
111 spin_unlock(&r->consumer_lock);
117 static struct page *__page_pool_alloc_pages_slow(struct page_pool *pool,
124 /* We could always set __GFP_COMP, and avoid this branch, as
125 * prep_new_page() can handle order-0 with __GFP_COMP.
130 /* FUTURE development:
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.
137 /* Cache was empty, do real allocation */
138 page = alloc_pages_node(pool->p.nid, gfp, pool->p.order);
142 if (!(pool->p.flags & PP_FLAG_DMA_MAP))
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.
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)) {
157 page->dma_addr = dma;
160 /* Track how many pages are held 'in-flight' */
161 pool->pages_state_hold_cnt++;
163 trace_page_pool_state_hold(pool, page, pool->pages_state_hold_cnt);
165 /* When page just alloc'ed is should/must have refcnt 1. */
169 /* For using page_pool replace: alloc_pages() API calls, but provide
170 * synchronization guarantee for allocation side.
172 struct page *page_pool_alloc_pages(struct page_pool *pool, gfp_t gfp)
176 /* Fast-path: Get a page from cache */
177 page = __page_pool_get_cached(pool);
181 /* Slow-path: cache empty, do real allocation */
182 page = __page_pool_alloc_pages_slow(pool, gfp);
185 EXPORT_SYMBOL(page_pool_alloc_pages);
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
190 #define _distance(a, b) (s32)((a) - (b))
192 static s32 page_pool_inflight(struct page_pool *pool)
194 u32 release_cnt = atomic_read(&pool->pages_state_release_cnt);
195 u32 hold_cnt = READ_ONCE(pool->pages_state_hold_cnt);
198 distance = _distance(hold_cnt, release_cnt);
200 trace_page_pool_inflight(pool, distance, hold_cnt, release_cnt);
204 static bool __page_pool_safe_to_destroy(struct page_pool *pool)
206 s32 inflight = page_pool_inflight(pool);
208 /* The distance should not be able to become negative */
209 WARN(inflight < 0, "Negative(%d) inflight packet-pages", inflight);
211 return (inflight == 0);
214 /* Cleanup page_pool state from page */
215 static void __page_pool_clean_page(struct page_pool *pool,
220 if (!(pool->p.flags & PP_FLAG_DMA_MAP))
223 dma = page->dma_addr;
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);
230 atomic_inc(&pool->pages_state_release_cnt);
231 trace_page_pool_state_release(pool, page,
232 atomic_read(&pool->pages_state_release_cnt));
235 /* unmap the page and clean our state */
236 void page_pool_unmap_page(struct page_pool *pool, struct page *page)
238 /* When page is unmapped, this implies page will not be
239 * returned to page_pool.
241 __page_pool_clean_page(pool, page);
243 EXPORT_SYMBOL(page_pool_unmap_page);
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)
248 __page_pool_clean_page(pool, 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).
257 static bool __page_pool_recycle_into_ring(struct page_pool *pool,
261 /* BH protection not needed if current is serving softirq */
262 if (in_serving_softirq())
263 ret = ptr_ring_produce(&pool->ring, page);
265 ret = ptr_ring_produce_bh(&pool->ring, page);
267 return (ret == 0) ? true : false;
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.
273 * Caller must provide appropriate safe context.
275 static bool __page_pool_recycle_direct(struct page *page,
276 struct page_pool *pool)
278 if (unlikely(pool->alloc.count == PP_ALLOC_CACHE_SIZE))
281 /* Caller MUST have verified/know (page_ref_count(page) == 1) */
282 pool->alloc.cache[pool->alloc.count++] = page;
286 void __page_pool_put_page(struct page_pool *pool,
287 struct page *page, bool allow_direct)
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.
293 * refcnt == 1 means page_pool owns page, and can recycle it.
295 if (likely(page_ref_count(page) == 1)) {
296 /* Read barrier done in page_ref_count / READ_ONCE */
298 if (allow_direct && in_serving_softirq())
299 if (__page_pool_recycle_direct(page, pool))
302 if (!__page_pool_recycle_into_ring(pool, page)) {
303 /* Cache full, fallback to free pages */
304 __page_pool_return_page(pool, page);
308 /* Fallback/non-XDP mode: API user have elevated refcnt.
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.
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.
321 __page_pool_clean_page(pool, page);
324 EXPORT_SYMBOL(__page_pool_put_page);
326 static void __page_pool_empty_ring(struct page_pool *pool)
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));
337 __page_pool_return_page(pool, page);
341 static void __warn_in_flight(struct page_pool *pool)
343 u32 release_cnt = atomic_read(&pool->pages_state_release_cnt);
344 u32 hold_cnt = READ_ONCE(pool->pages_state_hold_cnt);
347 distance = _distance(hold_cnt, release_cnt);
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);
354 void __page_pool_free(struct page_pool *pool)
356 /* Only last user actually free/release resources */
357 if (!page_pool_put(pool))
360 WARN(pool->alloc.count, "API usage violation");
361 WARN(!ptr_ring_empty(&pool->ring), "ptr_ring is not empty");
363 /* Can happen due to forced shutdown */
364 if (!__page_pool_safe_to_destroy(pool))
365 __warn_in_flight(pool);
367 ptr_ring_cleanup(&pool->ring, NULL);
369 if (pool->p.flags & PP_FLAG_DMA_MAP)
370 put_device(pool->p.dev);
374 EXPORT_SYMBOL(__page_pool_free);
376 /* Request to shutdown: release pages cached by page_pool, and check
377 * for in-flight pages
379 bool __page_pool_request_shutdown(struct page_pool *pool)
383 /* Empty alloc cache, assume caller made sure this is
384 * no-longer in use, and page_pool_alloc_pages() cannot be
387 while (pool->alloc.count) {
388 page = pool->alloc.cache[--pool->alloc.count];
389 __page_pool_return_page(pool, page);
392 /* No more consumers should exist, but producers could still
395 __page_pool_empty_ring(pool);
397 return __page_pool_safe_to_destroy(pool);
399 EXPORT_SYMBOL(__page_pool_request_shutdown);