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/* SPDX-License-Identifier: GPL-2.0
*
* page_pool/helpers.h
* Author: Jesper Dangaard Brouer <netoptimizer@brouer.com>
* Copyright (C) 2016 Red Hat, Inc.
*/
/**
* DOC: page_pool allocator
*
* The page_pool allocator is optimized for recycling page or page fragment used
* by skb packet and xdp frame.
*
* Basic use involves replacing any alloc_pages() calls with page_pool_alloc(),
* which allocate memory with or without page splitting depending on the
* requested memory size.
*
* If the driver knows that it always requires full pages or its allocations are
* always smaller than half a page, it can use one of the more specific API
* calls:
*
* 1. page_pool_alloc_pages(): allocate memory without page splitting when
* driver knows that the memory it need is always bigger than half of the page
* allocated from page pool. There is no cache line dirtying for 'struct page'
* when a page is recycled back to the page pool.
*
* 2. page_pool_alloc_frag(): allocate memory with page splitting when driver
* knows that the memory it need is always smaller than or equal to half of the
* page allocated from page pool. Page splitting enables memory saving and thus
* avoids TLB/cache miss for data access, but there also is some cost to
* implement page splitting, mainly some cache line dirtying/bouncing for
* 'struct page' and atomic operation for page->pp_ref_count.
*
* The API keeps track of in-flight pages, in order to let API users know when
* it is safe to free a page_pool object, the API users must call
* page_pool_put_page() or page_pool_free_va() to free the page_pool object, or
* attach the page_pool object to a page_pool-aware object like skbs marked with
* skb_mark_for_recycle().
*
* page_pool_put_page() may be called multiple times on the same page if a page
* is split into multiple fragments. For the last fragment, it will either
* recycle the page, or in case of page->_refcount > 1, it will release the DMA
* mapping and in-flight state accounting.
*
* dma_sync_single_range_for_device() is only called for the last fragment when
* page_pool is created with PP_FLAG_DMA_SYNC_DEV flag, so it depends on the
* last freed fragment to do the sync_for_device operation for all fragments in
* the same page when a page is split. The API user must setup pool->p.max_len
* and pool->p.offset correctly and ensure that page_pool_put_page() is called
* with dma_sync_size being -1 for fragment API.
*/
#ifndef _NET_PAGE_POOL_HELPERS_H
#define _NET_PAGE_POOL_HELPERS_H
#include <net/page_pool/types.h>
#ifdef CONFIG_PAGE_POOL_STATS
/* Deprecated driver-facing API, use netlink instead */
int page_pool_ethtool_stats_get_count(void);
u8 *page_pool_ethtool_stats_get_strings(u8 *data);
u64 *page_pool_ethtool_stats_get(u64 *data, void *stats);
bool page_pool_get_stats(const struct page_pool *pool,
struct page_pool_stats *stats);
#else
static inline int page_pool_ethtool_stats_get_count(void)
{
return 0;
}
static inline u8 *page_pool_ethtool_stats_get_strings(u8 *data)
{
return data;
}
static inline u64 *page_pool_ethtool_stats_get(u64 *data, void *stats)
{
return data;
}
#endif
/**
* page_pool_dev_alloc_pages() - allocate a page.
* @pool: pool from which to allocate
*
* Get a page from the page allocator or page_pool caches.
*/
static inline struct page *page_pool_dev_alloc_pages(struct page_pool *pool)
{
gfp_t gfp = (GFP_ATOMIC | __GFP_NOWARN);
return page_pool_alloc_pages(pool, gfp);
}
/**
* page_pool_dev_alloc_frag() - allocate a page fragment.
* @pool: pool from which to allocate
* @offset: offset to the allocated page
* @size: requested size
*
* Get a page fragment from the page allocator or page_pool caches.
*
* Return:
* Return allocated page fragment, otherwise return NULL.
*/
static inline struct page *page_pool_dev_alloc_frag(struct page_pool *pool,
unsigned int *offset,
unsigned int size)
{
gfp_t gfp = (GFP_ATOMIC | __GFP_NOWARN);
return page_pool_alloc_frag(pool, offset, size, gfp);
}
static inline struct page *page_pool_alloc(struct page_pool *pool,
unsigned int *offset,
unsigned int *size, gfp_t gfp)
{
unsigned int max_size = PAGE_SIZE << pool->p.order;
struct page *page;
if ((*size << 1) > max_size) {
*size = max_size;
*offset = 0;
return page_pool_alloc_pages(pool, gfp);
}
page = page_pool_alloc_frag(pool, offset, *size, gfp);
if (unlikely(!page))
return NULL;
/* There is very likely not enough space for another fragment, so append
* the remaining size to the current fragment to avoid truesize
* underestimate problem.
*/
if (pool->frag_offset + *size > max_size) {
*size = max_size - *offset;
pool->frag_offset = max_size;
}
return page;
}
/**
* page_pool_dev_alloc() - allocate a page or a page fragment.
* @pool: pool from which to allocate
* @offset: offset to the allocated page
* @size: in as the requested size, out as the allocated size
*
* Get a page or a page fragment from the page allocator or page_pool caches
* depending on the requested size in order to allocate memory with least memory
* utilization and performance penalty.
*
* Return:
* Return allocated page or page fragment, otherwise return NULL.
*/
static inline struct page *page_pool_dev_alloc(struct page_pool *pool,
unsigned int *offset,
unsigned int *size)
{
gfp_t gfp = (GFP_ATOMIC | __GFP_NOWARN);
return page_pool_alloc(pool, offset, size, gfp);
}
static inline void *page_pool_alloc_va(struct page_pool *pool,
unsigned int *size, gfp_t gfp)
{
unsigned int offset;
struct page *page;
/* Mask off __GFP_HIGHMEM to ensure we can use page_address() */
page = page_pool_alloc(pool, &offset, size, gfp & ~__GFP_HIGHMEM);
if (unlikely(!page))
return NULL;
return page_address(page) + offset;
}
/**
* page_pool_dev_alloc_va() - allocate a page or a page fragment and return its
* va.
* @pool: pool from which to allocate
* @size: in as the requested size, out as the allocated size
*
* This is just a thin wrapper around the page_pool_alloc() API, and
* it returns va of the allocated page or page fragment.
*
* Return:
* Return the va for the allocated page or page fragment, otherwise return NULL.
*/
static inline void *page_pool_dev_alloc_va(struct page_pool *pool,
unsigned int *size)
{
gfp_t gfp = (GFP_ATOMIC | __GFP_NOWARN);
return page_pool_alloc_va(pool, size, gfp);
}
/**
* page_pool_get_dma_dir() - Retrieve the stored DMA direction.
* @pool: pool from which page was allocated
*
* Get the stored dma direction. A driver might decide to store this locally
* and avoid the extra cache line from page_pool to determine the direction.
*/
static
inline enum dma_data_direction page_pool_get_dma_dir(struct page_pool *pool)
{
return pool->p.dma_dir;
}
/**
* page_pool_fragment_page() - split a fresh page into fragments
* @page: page to split
* @nr: references to set
*
* pp_ref_count represents the number of outstanding references to the page,
* which will be freed using page_pool APIs (rather than page allocator APIs
* like put_page()). Such references are usually held by page_pool-aware
* objects like skbs marked for page pool recycling.
*
* This helper allows the caller to take (set) multiple references to a
* freshly allocated page. The page must be freshly allocated (have a
* pp_ref_count of 1). This is commonly done by drivers and
* "fragment allocators" to save atomic operations - either when they know
* upfront how many references they will need; or to take MAX references and
* return the unused ones with a single atomic dec(), instead of performing
* multiple atomic inc() operations.
*/
static inline void page_pool_fragment_page(struct page *page, long nr)
{
atomic_long_set(&page->pp_ref_count, nr);
}
static inline long page_pool_unref_page(struct page *page, long nr)
{
long ret;
/* If nr == pp_ref_count then we have cleared all remaining
* references to the page:
* 1. 'n == 1': no need to actually overwrite it.
* 2. 'n != 1': overwrite it with one, which is the rare case
* for pp_ref_count draining.
*
* The main advantage to doing this is that not only we avoid a atomic
* update, as an atomic_read is generally a much cheaper operation than
* an atomic update, especially when dealing with a page that may be
* referenced by only 2 or 3 users; but also unify the pp_ref_count
* handling by ensuring all pages have partitioned into only 1 piece
* initially, and only overwrite it when the page is partitioned into
* more than one piece.
*/
if (atomic_long_read(&page->pp_ref_count) == nr) {
/* As we have ensured nr is always one for constant case using
* the BUILD_BUG_ON(), only need to handle the non-constant case
* here for pp_ref_count draining, which is a rare case.
*/
BUILD_BUG_ON(__builtin_constant_p(nr) && nr != 1);
if (!__builtin_constant_p(nr))
atomic_long_set(&page->pp_ref_count, 1);
return 0;
}
ret = atomic_long_sub_return(nr, &page->pp_ref_count);
WARN_ON(ret < 0);
/* We are the last user here too, reset pp_ref_count back to 1 to
* ensure all pages have been partitioned into 1 piece initially,
* this should be the rare case when the last two fragment users call
* page_pool_unref_page() currently.
*/
if (unlikely(!ret))
atomic_long_set(&page->pp_ref_count, 1);
return ret;
}
static inline void page_pool_ref_page(struct page *page)
{
atomic_long_inc(&page->pp_ref_count);
}
static inline bool page_pool_is_last_ref(struct page *page)
{
/* If page_pool_unref_page() returns 0, we were the last user */
return page_pool_unref_page(page, 1) == 0;
}
/**
* page_pool_put_page() - release a reference to a page pool page
* @pool: pool from which page was allocated
* @page: page to release a reference on
* @dma_sync_size: how much of the page may have been touched by the device
* @allow_direct: released by the consumer, allow lockless caching
*
* The outcome of this depends on the page refcnt. If the driver bumps
* the refcnt > 1 this will unmap the page. If the page refcnt is 1
* the allocator owns the page and will try to recycle it in one of the pool
* caches. If PP_FLAG_DMA_SYNC_DEV is set, the page will be synced for_device
* using dma_sync_single_range_for_device().
*/
static inline void page_pool_put_page(struct page_pool *pool,
struct page *page,
unsigned int dma_sync_size,
bool allow_direct)
{
/* When page_pool isn't compiled-in, net/core/xdp.c doesn't
* allow registering MEM_TYPE_PAGE_POOL, but shield linker.
*/
#ifdef CONFIG_PAGE_POOL
if (!page_pool_is_last_ref(page))
return;
page_pool_put_unrefed_page(pool, page, dma_sync_size, allow_direct);
#endif
}
/**
* page_pool_put_full_page() - release a reference on a page pool page
* @pool: pool from which page was allocated
* @page: page to release a reference on
* @allow_direct: released by the consumer, allow lockless caching
*
* Similar to page_pool_put_page(), but will DMA sync the entire memory area
* as configured in &page_pool_params.max_len.
*/
static inline void page_pool_put_full_page(struct page_pool *pool,
struct page *page, bool allow_direct)
{
page_pool_put_page(pool, page, -1, allow_direct);
}
/**
* page_pool_recycle_direct() - release a reference on a page pool page
* @pool: pool from which page was allocated
* @page: page to release a reference on
*
* Similar to page_pool_put_full_page() but caller must guarantee safe context
* (e.g NAPI), since it will recycle the page directly into the pool fast cache.
*/
static inline void page_pool_recycle_direct(struct page_pool *pool,
struct page *page)
{
page_pool_put_full_page(pool, page, true);
}
#define PAGE_POOL_32BIT_ARCH_WITH_64BIT_DMA \
(sizeof(dma_addr_t) > sizeof(unsigned long))
/**
* page_pool_free_va() - free a va into the page_pool
* @pool: pool from which va was allocated
* @va: va to be freed
* @allow_direct: freed by the consumer, allow lockless caching
*
* Free a va allocated from page_pool_allo_va().
*/
static inline void page_pool_free_va(struct page_pool *pool, void *va,
bool allow_direct)
{
page_pool_put_page(pool, virt_to_head_page(va), -1, allow_direct);
}
/**
* page_pool_get_dma_addr() - Retrieve the stored DMA address.
* @page: page allocated from a page pool
*
* Fetch the DMA address of the page. The page pool to which the page belongs
* must had been created with PP_FLAG_DMA_MAP.
*/
static inline dma_addr_t page_pool_get_dma_addr(struct page *page)
{
dma_addr_t ret = page->dma_addr;
if (PAGE_POOL_32BIT_ARCH_WITH_64BIT_DMA)
ret <<= PAGE_SHIFT;
return ret;
}
static inline bool page_pool_set_dma_addr(struct page *page, dma_addr_t addr)
{
if (PAGE_POOL_32BIT_ARCH_WITH_64BIT_DMA) {
page->dma_addr = addr >> PAGE_SHIFT;
/* We assume page alignment to shave off bottom bits,
* if this "compression" doesn't work we need to drop.
*/
return addr != (dma_addr_t)page->dma_addr << PAGE_SHIFT;
}
page->dma_addr = addr;
return false;
}
static inline bool page_pool_put(struct page_pool *pool)
{
return refcount_dec_and_test(&pool->user_cnt);
}
static inline void page_pool_nid_changed(struct page_pool *pool, int new_nid)
{
if (unlikely(pool->p.nid != new_nid))
page_pool_update_nid(pool, new_nid);
}
#endif /* _NET_PAGE_POOL_HELPERS_H */