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 the XDP mode that
12  * uses one frame per-page, but it can fallback on the
13  * regular page allocator APIs.
14  *
15  * Basic use involves replacing alloc_pages() calls with the
16  * page_pool_alloc_pages() call.  Drivers should use
17  * page_pool_dev_alloc_pages() replacing dev_alloc_pages().
18  *
19  * The API keeps track of in-flight pages, in order to let API users know
20  * when it is safe to free a page_pool object.  Thus, API users
21  * must call page_pool_put_page() to free the page, or attach
22  * the page to a page_pool-aware object like skbs marked with
23  * skb_mark_for_recycle().
24  *
25  * API users must call page_pool_put_page() once on a page, as it
26  * will either recycle the page, or in case of refcnt > 1, it will
27  * release the DMA mapping and in-flight state accounting.
28  */
29 #ifndef _NET_PAGE_POOL_HELPERS_H
30 #define _NET_PAGE_POOL_HELPERS_H
31 
32 #include <net/page_pool/types.h>
33 
34 #ifdef CONFIG_PAGE_POOL_STATS
35 int page_pool_ethtool_stats_get_count(void);
36 u8 *page_pool_ethtool_stats_get_strings(u8 *data);
37 u64 *page_pool_ethtool_stats_get(u64 *data, void *stats);
38 
39 /*
40  * Drivers that wish to harvest page pool stats and report them to users
41  * (perhaps via ethtool, debugfs, or another mechanism) can allocate a
42  * struct page_pool_stats call page_pool_get_stats to get stats for the specified pool.
43  */
44 bool page_pool_get_stats(struct page_pool *pool,
45 			 struct page_pool_stats *stats);
46 #else
page_pool_ethtool_stats_get_count(void)47 static inline int page_pool_ethtool_stats_get_count(void)
48 {
49 	return 0;
50 }
51 
page_pool_ethtool_stats_get_strings(u8 * data)52 static inline u8 *page_pool_ethtool_stats_get_strings(u8 *data)
53 {
54 	return data;
55 }
56 
page_pool_ethtool_stats_get(u64 * data,void * stats)57 static inline u64 *page_pool_ethtool_stats_get(u64 *data, void *stats)
58 {
59 	return data;
60 }
61 #endif
62 
63 /**
64  * page_pool_dev_alloc_pages() - allocate a page.
65  * @pool:	pool from which to allocate
66  *
67  * Get a page from the page allocator or page_pool caches.
68  */
page_pool_dev_alloc_pages(struct page_pool * pool)69 static inline struct page *page_pool_dev_alloc_pages(struct page_pool *pool)
70 {
71 	gfp_t gfp = (GFP_ATOMIC | __GFP_NOWARN);
72 
73 	return page_pool_alloc_pages(pool, gfp);
74 }
75 
page_pool_dev_alloc_frag(struct page_pool * pool,unsigned int * offset,unsigned int size)76 static inline struct page *page_pool_dev_alloc_frag(struct page_pool *pool,
77 						    unsigned int *offset,
78 						    unsigned int size)
79 {
80 	gfp_t gfp = (GFP_ATOMIC | __GFP_NOWARN);
81 
82 	return page_pool_alloc_frag(pool, offset, size, gfp);
83 }
84 
85 /**
86  * page_pool_get_dma_dir() - Retrieve the stored DMA direction.
87  * @pool:	pool from which page was allocated
88  *
89  * Get the stored dma direction. A driver might decide to store this locally
90  * and avoid the extra cache line from page_pool to determine the direction.
91  */
92 static
page_pool_get_dma_dir(struct page_pool * pool)93 inline enum dma_data_direction page_pool_get_dma_dir(struct page_pool *pool)
94 {
95 	return pool->p.dma_dir;
96 }
97 
98 /* pp_frag_count represents the number of writers who can update the page
99  * either by updating skb->data or via DMA mappings for the device.
100  * We can't rely on the page refcnt for that as we don't know who might be
101  * holding page references and we can't reliably destroy or sync DMA mappings
102  * of the fragments.
103  *
104  * When pp_frag_count reaches 0 we can either recycle the page if the page
105  * refcnt is 1 or return it back to the memory allocator and destroy any
106  * mappings we have.
107  */
page_pool_fragment_page(struct page * page,long nr)108 static inline void page_pool_fragment_page(struct page *page, long nr)
109 {
110 	atomic_long_set(&page->pp_frag_count, nr);
111 }
112 
page_pool_defrag_page(struct page * page,long nr)113 static inline long page_pool_defrag_page(struct page *page, long nr)
114 {
115 	long ret;
116 
117 	/* If nr == pp_frag_count then we have cleared all remaining
118 	 * references to the page. No need to actually overwrite it, instead
119 	 * we can leave this to be overwritten by the calling function.
120 	 *
121 	 * The main advantage to doing this is that an atomic_read is
122 	 * generally a much cheaper operation than an atomic update,
123 	 * especially when dealing with a page that may be partitioned
124 	 * into only 2 or 3 pieces.
125 	 */
126 	if (atomic_long_read(&page->pp_frag_count) == nr)
127 		return 0;
128 
129 	ret = atomic_long_sub_return(nr, &page->pp_frag_count);
130 	WARN_ON(ret < 0);
131 	return ret;
132 }
133 
page_pool_is_last_frag(struct page_pool * pool,struct page * page)134 static inline bool page_pool_is_last_frag(struct page_pool *pool,
135 					  struct page *page)
136 {
137 	/* If fragments aren't enabled or count is 0 we were the last user */
138 	return !(pool->p.flags & PP_FLAG_PAGE_FRAG) ||
139 	       (page_pool_defrag_page(page, 1) == 0);
140 }
141 
142 /**
143  * page_pool_put_page() - release a reference to a page pool page
144  * @pool:	pool from which page was allocated
145  * @page:	page to release a reference on
146  * @dma_sync_size: how much of the page may have been touched by the device
147  * @allow_direct: released by the consumer, allow lockless caching
148  *
149  * The outcome of this depends on the page refcnt. If the driver bumps
150  * the refcnt > 1 this will unmap the page. If the page refcnt is 1
151  * the allocator owns the page and will try to recycle it in one of the pool
152  * caches. If PP_FLAG_DMA_SYNC_DEV is set, the page will be synced for_device
153  * using dma_sync_single_range_for_device().
154  */
page_pool_put_page(struct page_pool * pool,struct page * page,unsigned int dma_sync_size,bool allow_direct)155 static inline void page_pool_put_page(struct page_pool *pool,
156 				      struct page *page,
157 				      unsigned int dma_sync_size,
158 				      bool allow_direct)
159 {
160 	/* When page_pool isn't compiled-in, net/core/xdp.c doesn't
161 	 * allow registering MEM_TYPE_PAGE_POOL, but shield linker.
162 	 */
163 #ifdef CONFIG_PAGE_POOL
164 	if (!page_pool_is_last_frag(pool, page))
165 		return;
166 
167 	page_pool_put_defragged_page(pool, page, dma_sync_size, allow_direct);
168 #endif
169 }
170 
171 /**
172  * page_pool_put_full_page() - release a reference on a page pool page
173  * @pool:	pool from which page was allocated
174  * @page:	page to release a reference on
175  * @allow_direct: released by the consumer, allow lockless caching
176  *
177  * Similar to page_pool_put_page(), but will DMA sync the entire memory area
178  * as configured in &page_pool_params.max_len.
179  */
page_pool_put_full_page(struct page_pool * pool,struct page * page,bool allow_direct)180 static inline void page_pool_put_full_page(struct page_pool *pool,
181 					   struct page *page, bool allow_direct)
182 {
183 	page_pool_put_page(pool, page, -1, allow_direct);
184 }
185 
186 /**
187  * page_pool_recycle_direct() - release a reference on a page pool page
188  * @pool:	pool from which page was allocated
189  * @page:	page to release a reference on
190  *
191  * Similar to page_pool_put_full_page() but caller must guarantee safe context
192  * (e.g NAPI), since it will recycle the page directly into the pool fast cache.
193  */
page_pool_recycle_direct(struct page_pool * pool,struct page * page)194 static inline void page_pool_recycle_direct(struct page_pool *pool,
195 					    struct page *page)
196 {
197 	page_pool_put_full_page(pool, page, true);
198 }
199 
200 #define PAGE_POOL_DMA_USE_PP_FRAG_COUNT	\
201 		(sizeof(dma_addr_t) > sizeof(unsigned long))
202 
203 /**
204  * page_pool_get_dma_addr() - Retrieve the stored DMA address.
205  * @page:	page allocated from a page pool
206  *
207  * Fetch the DMA address of the page. The page pool to which the page belongs
208  * must had been created with PP_FLAG_DMA_MAP.
209  */
page_pool_get_dma_addr(struct page * page)210 static inline dma_addr_t page_pool_get_dma_addr(struct page *page)
211 {
212 	dma_addr_t ret = page->dma_addr;
213 
214 	if (PAGE_POOL_DMA_USE_PP_FRAG_COUNT)
215 		ret |= (dma_addr_t)page->dma_addr_upper << 16 << 16;
216 
217 	return ret;
218 }
219 
page_pool_set_dma_addr(struct page * page,dma_addr_t addr)220 static inline void page_pool_set_dma_addr(struct page *page, dma_addr_t addr)
221 {
222 	page->dma_addr = addr;
223 	if (PAGE_POOL_DMA_USE_PP_FRAG_COUNT)
224 		page->dma_addr_upper = upper_32_bits(addr);
225 }
226 
page_pool_put(struct page_pool * pool)227 static inline bool page_pool_put(struct page_pool *pool)
228 {
229 	return refcount_dec_and_test(&pool->user_cnt);
230 }
231 
page_pool_nid_changed(struct page_pool * pool,int new_nid)232 static inline void page_pool_nid_changed(struct page_pool *pool, int new_nid)
233 {
234 	if (unlikely(pool->p.nid != new_nid))
235 		page_pool_update_nid(pool, new_nid);
236 }
237 
238 #endif /* _NET_PAGE_POOL_HELPERS_H */
239