11  * The page_pool allocator is optimized for recycling page or page fragment used
15  * which allocate memory with or without page splitting depending on the
19  * always smaller than half a page, it can use one of the more specific API
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.
27  * 2. page_pool_alloc_frag(): allocate memory with page splitting when driver
29  * page allocated from page pool. Page splitting enables memory saving and thus
31  * implement page splitting, mainly some cache line dirtying/bouncing for
32  * 'struct page' and atomic operation for page->pp_ref_count.
40  * page_pool_put_page() may be called multiple times on the same page if a page
42  * recycle the page, or in case of page->_refcount > 1, it will release the DMA
48  * the same page when a page is split. The API user must setup pool->p.max_len
83  * page_pool_dev_alloc_pages() - allocate a page.
86  * Get a page from the page allocator or page_pool caches.
88 static inline struct page *page_pool_dev_alloc_pages(struct page_pool *pool)  in page_pool_dev_alloc_pages()
96  * page_pool_dev_alloc_frag() - allocate a page fragment.
98  * @offset: offset to the allocated page
101  * Get a page fragment from the page allocator or page_pool caches.
104  * Return allocated page fragment, otherwise return NULL.
106 static inline struct page *page_pool_dev_alloc_frag(struct page_pool *pool,  in page_pool_dev_alloc_frag()
115 static inline struct page *page_pool_alloc(struct page_pool *pool,  in page_pool_alloc()
120 	struct page *page;  in page_pool_alloc()  local
128 	page = page_pool_alloc_frag(pool, offset, *size, gfp);  in page_pool_alloc()
129 	if (unlikely(!page))  in page_pool_alloc()
141 	return page;  in page_pool_alloc()
145  * page_pool_dev_alloc() - allocate a page or a page fragment.
147  * @offset: offset to the allocated page
150  * Get a page or a page fragment from the page allocator or page_pool caches
155  * Return allocated page or page fragment, otherwise return NULL.
157 static inline struct page *page_pool_dev_alloc(struct page_pool *pool,  in page_pool_dev_alloc()
170 	struct page *page;  in page_pool_alloc_va()  local
173 	page = page_pool_alloc(pool, &offset, size, gfp & ~__GFP_HIGHMEM);  in page_pool_alloc_va()
174 	if (unlikely(!page))  in page_pool_alloc_va()
177 	return page_address(page) + offset;  in page_pool_alloc_va()
181  * page_pool_dev_alloc_va() - allocate a page or a page fragment and return its
187  * it returns va of the allocated page or page fragment.
190  * Return the va for the allocated page or page fragment, otherwise return NULL.
202  * @pool:	pool from which page was allocated
214  * page_pool_fragment_page() - split a fresh page into fragments
215  * @page:	page to split
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
221  * objects like skbs marked for page pool recycling.
224  * freshly allocated page. The page must be freshly allocated (have a
231 static inline void page_pool_fragment_page(struct page *page, long nr)  in page_pool_fragment_page()  argument
233 	atomic_long_set(&page->pp_ref_count, nr);  in page_pool_fragment_page()
236 static inline long page_pool_unref_page(struct page *page, long nr)  in page_pool_unref_page()  argument
241 	 * references to the page:  in page_pool_unref_page()
248 	 * an atomic update, especially when dealing with a page that may be  in page_pool_unref_page()
251 	 * initially, and only overwrite it when the page is partitioned into  in page_pool_unref_page()
254 	if (atomic_long_read(&page->pp_ref_count) == nr) {  in page_pool_unref_page()
261 			atomic_long_set(&page->pp_ref_count, 1);  in page_pool_unref_page()
266 	ret = atomic_long_sub_return(nr, &page->pp_ref_count);  in page_pool_unref_page()
275 		atomic_long_set(&page->pp_ref_count, 1);  in page_pool_unref_page()
280 static inline void page_pool_ref_page(struct page *page)  in page_pool_ref_page()  argument
282 	atomic_long_inc(&page->pp_ref_count);  in page_pool_ref_page()
285 static inline bool page_pool_is_last_ref(struct page *page)  in page_pool_is_last_ref()  argument
288 	return page_pool_unref_page(page, 1) == 0;  in page_pool_is_last_ref()
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
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
305 				      struct page *page,  in page_pool_put_page()  argument
313 	if (!page_pool_is_last_ref(page))  in page_pool_put_page()
316 	page_pool_put_unrefed_page(pool, page, dma_sync_size, allow_direct);  in page_pool_put_page()
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
330 					   struct page *page, bool allow_direct)  in page_pool_put_full_page()  argument
332 	page_pool_put_page(pool, page, -1, allow_direct);  in page_pool_put_full_page()
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
341  * (e.g NAPI), since it will recycle the page directly into the pool fast cache.
344 					    struct page *page)  in page_pool_recycle_direct()  argument
346 	page_pool_put_full_page(pool, page, true);  in page_pool_recycle_direct()
368  * @page:	page allocated from a page pool
370  * Fetch the DMA address of the page. The page pool to which the page belongs
373 static inline dma_addr_t page_pool_get_dma_addr(struct page *page)  in page_pool_get_dma_addr()  argument
375 	dma_addr_t ret = page->dma_addr;  in page_pool_get_dma_addr()
383 static inline bool page_pool_set_dma_addr(struct page *page, dma_addr_t addr)  in page_pool_set_dma_addr()  argument
386 		page->dma_addr = addr >> PAGE_SHIFT;  in page_pool_set_dma_addr()
388 		/* We assume page alignment to shave off bottom bits,  in page_pool_set_dma_addr()
391 		return addr != (dma_addr_t)page->dma_addr << PAGE_SHIFT;  in page_pool_set_dma_addr()
394 	page->dma_addr = addr;  in page_pool_set_dma_addr()