1/* SPDX-License-Identifier: GPL-2.0
  2 *
  3 * page_pool.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 * This page_pool allocator is optimized for the XDP mode that
 12 * uses one-frame-per-page, but have fallbacks that act like the
 13 * regular page allocator APIs.
 14 *
 15 * Basic use involve replacing alloc_pages() calls with the
 16 * page_pool_alloc_pages() call.  Drivers should likely use
 17 * page_pool_dev_alloc_pages() replacing dev_alloc_pages().
 18 *
 19 * API keeps track of in-flight pages, in-order to let API user know
 20 * when it is safe to dealloactor page_pool object.  Thus, API users
 21 * must make sure to call page_pool_release_page() when a page is
 22 * "leaving" the page_pool.  Or call page_pool_put_page() where
 23 * appropiate.  For maintaining correct accounting.
 24 *
 25 * API user must only call page_pool_put_page() once on a page, as it
 26 * will either recycle the page, or in case of elevated refcnt, it
 27 * will release the DMA mapping and in-flight state accounting.  We
 28 * hope to lift this requirement in the future.
 29 */
 30#ifndef _NET_PAGE_POOL_H
 31#define _NET_PAGE_POOL_H
 32
 33#include <linux/mm.h> /* Needed by ptr_ring */
 34#include <linux/ptr_ring.h>
 35#include <linux/dma-direction.h>
 36
 37#define PP_FLAG_DMA_MAP		BIT(0) /* Should page_pool do the DMA
 38					* map/unmap
 39					*/
 40#define PP_FLAG_DMA_SYNC_DEV	BIT(1) /* If set all pages that the driver gets
 41					* from page_pool will be
 42					* DMA-synced-for-device according to
 43					* the length provided by the device
 44					* driver.
 45					* Please note DMA-sync-for-CPU is still
 46					* device driver responsibility
 47					*/
 48#define PP_FLAG_PAGE_FRAG	BIT(2) /* for page frag feature */
 49#define PP_FLAG_ALL		(PP_FLAG_DMA_MAP |\
 50				 PP_FLAG_DMA_SYNC_DEV |\
 51				 PP_FLAG_PAGE_FRAG)
 52
 53/*
 54 * Fast allocation side cache array/stack
 55 *
 56 * The cache size and refill watermark is related to the network
 57 * use-case.  The NAPI budget is 64 packets.  After a NAPI poll the RX
 58 * ring is usually refilled and the max consumed elements will be 64,
 59 * thus a natural max size of objects needed in the cache.
 60 *
 61 * Keeping room for more objects, is due to XDP_DROP use-case.  As
 62 * XDP_DROP allows the opportunity to recycle objects directly into
 63 * this array, as it shares the same softirq/NAPI protection.  If
 64 * cache is already full (or partly full) then the XDP_DROP recycles
 65 * would have to take a slower code path.
 66 */
 67#define PP_ALLOC_CACHE_SIZE	128
 68#define PP_ALLOC_CACHE_REFILL	64
 69struct pp_alloc_cache {
 70	u32 count;
 71	struct page *cache[PP_ALLOC_CACHE_SIZE];
 72};
 73
 74struct page_pool_params {
 75	unsigned int	flags;
 76	unsigned int	order;
 77	unsigned int	pool_size;
 78	int		nid;  /* Numa node id to allocate from pages from */
 79	struct device	*dev; /* device, for DMA pre-mapping purposes */
 80	enum dma_data_direction dma_dir; /* DMA mapping direction */
 81	unsigned int	max_len; /* max DMA sync memory size */
 82	unsigned int	offset;  /* DMA addr offset */
 83	void (*init_callback)(struct page *page, void *arg);
 84	void *init_arg;
 85};
 86
 87#ifdef CONFIG_PAGE_POOL_STATS
 88struct page_pool_alloc_stats {
 89	u64 fast; /* fast path allocations */
 90	u64 slow; /* slow-path order 0 allocations */
 91	u64 slow_high_order; /* slow-path high order allocations */
 92	u64 empty; /* failed refills due to empty ptr ring, forcing
 93		    * slow path allocation
 94		    */
 95	u64 refill; /* allocations via successful refill */
 96	u64 waive;  /* failed refills due to numa zone mismatch */
 97};
 98
 99struct page_pool_recycle_stats {
100	u64 cached;	/* recycling placed page in the cache. */
101	u64 cache_full; /* cache was full */
102	u64 ring;	/* recycling placed page back into ptr ring */
103	u64 ring_full;	/* page was released from page-pool because
104			 * PTR ring was full.
105			 */
106	u64 released_refcnt; /* page released because of elevated
107			      * refcnt
108			      */
109};
110
111/* This struct wraps the above stats structs so users of the
112 * page_pool_get_stats API can pass a single argument when requesting the
113 * stats for the page pool.
114 */
115struct page_pool_stats {
116	struct page_pool_alloc_stats alloc_stats;
117	struct page_pool_recycle_stats recycle_stats;
118};
119
120int page_pool_ethtool_stats_get_count(void);
121u8 *page_pool_ethtool_stats_get_strings(u8 *data);
122u64 *page_pool_ethtool_stats_get(u64 *data, void *stats);
123
124/*
125 * Drivers that wish to harvest page pool stats and report them to users
126 * (perhaps via ethtool, debugfs, or another mechanism) can allocate a
127 * struct page_pool_stats call page_pool_get_stats to get stats for the specified pool.
128 */
129bool page_pool_get_stats(struct page_pool *pool,
130			 struct page_pool_stats *stats);
131#else
132
133static inline int page_pool_ethtool_stats_get_count(void)
134{
135	return 0;
136}
137
138static inline u8 *page_pool_ethtool_stats_get_strings(u8 *data)
139{
140	return data;
141}
142
143static inline u64 *page_pool_ethtool_stats_get(u64 *data, void *stats)
144{
145	return data;
146}
147
148#endif
149
150struct page_pool {
151	struct page_pool_params p;
152
153	struct delayed_work release_dw;
154	void (*disconnect)(void *);
155	unsigned long defer_start;
156	unsigned long defer_warn;
157
158	u32 pages_state_hold_cnt;
159	unsigned int frag_offset;
160	struct page *frag_page;
161	long frag_users;
162
163#ifdef CONFIG_PAGE_POOL_STATS
164	/* these stats are incremented while in softirq context */
165	struct page_pool_alloc_stats alloc_stats;
166#endif
167	u32 xdp_mem_id;
168
169	/*
170	 * Data structure for allocation side
171	 *
172	 * Drivers allocation side usually already perform some kind
173	 * of resource protection.  Piggyback on this protection, and
174	 * require driver to protect allocation side.
175	 *
176	 * For NIC drivers this means, allocate a page_pool per
177	 * RX-queue. As the RX-queue is already protected by
178	 * Softirq/BH scheduling and napi_schedule. NAPI schedule
179	 * guarantee that a single napi_struct will only be scheduled
180	 * on a single CPU (see napi_schedule).
181	 */
182	struct pp_alloc_cache alloc ____cacheline_aligned_in_smp;
183
184	/* Data structure for storing recycled pages.
185	 *
186	 * Returning/freeing pages is more complicated synchronization
187	 * wise, because free's can happen on remote CPUs, with no
188	 * association with allocation resource.
189	 *
190	 * Use ptr_ring, as it separates consumer and producer
191	 * effeciently, it a way that doesn't bounce cache-lines.
192	 *
193	 * TODO: Implement bulk return pages into this structure.
194	 */
195	struct ptr_ring ring;
196
197#ifdef CONFIG_PAGE_POOL_STATS
198	/* recycle stats are per-cpu to avoid locking */
199	struct page_pool_recycle_stats __percpu *recycle_stats;
200#endif
201	atomic_t pages_state_release_cnt;
202
203	/* A page_pool is strictly tied to a single RX-queue being
204	 * protected by NAPI, due to above pp_alloc_cache. This
205	 * refcnt serves purpose is to simplify drivers error handling.
206	 */
207	refcount_t user_cnt;
208
209	u64 destroy_cnt;
210};
211
212struct page *page_pool_alloc_pages(struct page_pool *pool, gfp_t gfp);
213
214static inline struct page *page_pool_dev_alloc_pages(struct page_pool *pool)
215{
216	gfp_t gfp = (GFP_ATOMIC | __GFP_NOWARN);
217
218	return page_pool_alloc_pages(pool, gfp);
219}
220
221struct page *page_pool_alloc_frag(struct page_pool *pool, unsigned int *offset,
222				  unsigned int size, gfp_t gfp);
223
224static inline struct page *page_pool_dev_alloc_frag(struct page_pool *pool,
225						    unsigned int *offset,
226						    unsigned int size)
227{
228	gfp_t gfp = (GFP_ATOMIC | __GFP_NOWARN);
229
230	return page_pool_alloc_frag(pool, offset, size, gfp);
231}
232
233/* get the stored dma direction. A driver might decide to treat this locally and
234 * avoid the extra cache line from page_pool to determine the direction
235 */
236static
237inline enum dma_data_direction page_pool_get_dma_dir(struct page_pool *pool)
238{
239	return pool->p.dma_dir;
240}
241
242bool page_pool_return_skb_page(struct page *page);
243
244struct page_pool *page_pool_create(const struct page_pool_params *params);
245
246struct xdp_mem_info;
247
248#ifdef CONFIG_PAGE_POOL
249void page_pool_destroy(struct page_pool *pool);
250void page_pool_use_xdp_mem(struct page_pool *pool, void (*disconnect)(void *),
251			   struct xdp_mem_info *mem);
252void page_pool_release_page(struct page_pool *pool, struct page *page);
253void page_pool_put_page_bulk(struct page_pool *pool, void **data,
254			     int count);
255#else
256static inline void page_pool_destroy(struct page_pool *pool)
257{
258}
259
260static inline void page_pool_use_xdp_mem(struct page_pool *pool,
261					 void (*disconnect)(void *),
262					 struct xdp_mem_info *mem)
263{
264}
265static inline void page_pool_release_page(struct page_pool *pool,
266					  struct page *page)
267{
268}
269
270static inline void page_pool_put_page_bulk(struct page_pool *pool, void **data,
271					   int count)
272{
273}
274#endif
275
276void page_pool_put_defragged_page(struct page_pool *pool, struct page *page,
277				  unsigned int dma_sync_size,
278				  bool allow_direct);
279
280static inline void page_pool_fragment_page(struct page *page, long nr)
281{
282	atomic_long_set(&page->pp_frag_count, nr);
283}
284
285static inline long page_pool_defrag_page(struct page *page, long nr)
286{
287	long ret;
288
289	/* If nr == pp_frag_count then we have cleared all remaining
290	 * references to the page. No need to actually overwrite it, instead
291	 * we can leave this to be overwritten by the calling function.
292	 *
293	 * The main advantage to doing this is that an atomic_read is
294	 * generally a much cheaper operation than an atomic update,
295	 * especially when dealing with a page that may be partitioned
296	 * into only 2 or 3 pieces.
297	 */
298	if (atomic_long_read(&page->pp_frag_count) == nr)
299		return 0;
300
301	ret = atomic_long_sub_return(nr, &page->pp_frag_count);
302	WARN_ON(ret < 0);
303	return ret;
304}
305
306static inline bool page_pool_is_last_frag(struct page_pool *pool,
307					  struct page *page)
308{
309	/* If fragments aren't enabled or count is 0 we were the last user */
310	return !(pool->p.flags & PP_FLAG_PAGE_FRAG) ||
311	       (page_pool_defrag_page(page, 1) == 0);
312}
313
314static inline void page_pool_put_page(struct page_pool *pool,
315				      struct page *page,
316				      unsigned int dma_sync_size,
317				      bool allow_direct)
318{
319	/* When page_pool isn't compiled-in, net/core/xdp.c doesn't
320	 * allow registering MEM_TYPE_PAGE_POOL, but shield linker.
321	 */
322#ifdef CONFIG_PAGE_POOL
323	if (!page_pool_is_last_frag(pool, page))
324		return;
325
326	page_pool_put_defragged_page(pool, page, dma_sync_size, allow_direct);
327#endif
328}
329
330/* Same as above but will try to sync the entire area pool->max_len */
331static inline void page_pool_put_full_page(struct page_pool *pool,
332					   struct page *page, bool allow_direct)
333{
334	page_pool_put_page(pool, page, -1, allow_direct);
335}
336
337/* Same as above but the caller must guarantee safe context. e.g NAPI */
338static inline void page_pool_recycle_direct(struct page_pool *pool,
339					    struct page *page)
340{
341	page_pool_put_full_page(pool, page, true);
342}
343
344#define PAGE_POOL_DMA_USE_PP_FRAG_COUNT	\
345		(sizeof(dma_addr_t) > sizeof(unsigned long))
346
347static inline dma_addr_t page_pool_get_dma_addr(struct page *page)
348{
349	dma_addr_t ret = page->dma_addr;
350
351	if (PAGE_POOL_DMA_USE_PP_FRAG_COUNT)
352		ret |= (dma_addr_t)page->dma_addr_upper << 16 << 16;
353
354	return ret;
355}
356
357static inline void page_pool_set_dma_addr(struct page *page, dma_addr_t addr)
358{
359	page->dma_addr = addr;
360	if (PAGE_POOL_DMA_USE_PP_FRAG_COUNT)
361		page->dma_addr_upper = upper_32_bits(addr);
362}
363
364static inline bool is_page_pool_compiled_in(void)
365{
366#ifdef CONFIG_PAGE_POOL
367	return true;
368#else
369	return false;
370#endif
371}
372
373static inline bool page_pool_put(struct page_pool *pool)
374{
375	return refcount_dec_and_test(&pool->user_cnt);
376}
377
378/* Caller must provide appropriate safe context, e.g. NAPI. */
379void page_pool_update_nid(struct page_pool *pool, int new_nid);
380static inline void page_pool_nid_changed(struct page_pool *pool, int new_nid)
381{
382	if (unlikely(pool->p.nid != new_nid))
383		page_pool_update_nid(pool, new_nid);
384}
385
386static inline void page_pool_ring_lock(struct page_pool *pool)
387	__acquires(&pool->ring.producer_lock)
388{
389	if (in_serving_softirq())
390		spin_lock(&pool->ring.producer_lock);
391	else
392		spin_lock_bh(&pool->ring.producer_lock);
393}
394
395static inline void page_pool_ring_unlock(struct page_pool *pool)
396	__releases(&pool->ring.producer_lock)
397{
398	if (in_serving_softirq())
399		spin_unlock(&pool->ring.producer_lock);
400	else
401		spin_unlock_bh(&pool->ring.producer_lock);
402}
403
404#endif /* _NET_PAGE_POOL_H */