All struct members of the driver-facing APIs are documented twice,
in the code and under Documentation. This is a bit tedious.
I also get the feeling that a lot of developers will read the header
when coding, rather than the doc. Bring the two a little closer
together by using kdoc for structs and functions.
Using kdoc also gives us links (mentioning a function or struct
in the text gets replaced by a link to its doc).
Signed-off-by: Jakub Kicinski <kuba@xxxxxxxxxx>
--
CC: hawk@xxxxxxxxxx
CC: ilias.apalodimas@xxxxxxxxxx
CC: corbet@xxxxxxx
CC: linux-doc@xxxxxxxxxxxxxxx
CC: Lorenzo Bianconi <lorenzo@xxxxxxxxxx>
CC: Randy Dunlap <rdunlap@xxxxxxxxxxxxx>
CC: Alexander Lobakin <aleksander.lobakin@xxxxxxxxx>
---
Documentation/networking/page_pool.rst | 86 ++++------------
include/net/page_pool.h | 134 +++++++++++++++++++------
net/core/page_pool.c | 31 +++++-
3 files changed, 152 insertions(+), 99 deletions(-)
diff --git a/Documentation/networking/page_pool.rst b/Documentation/networking/page_pool.rst
index eb96a592ec6b..53b5448cc0f1 100644
--- a/Documentation/networking/page_pool.rst
+++ b/Documentation/networking/page_pool.rst
@@ -64,50 +64,19 @@ This lockless guarantee naturally comes from running under a NAPI softirq.
The protection doesn't strictly have to be NAPI, any guarantee that allocating
a page will cause no race conditions is enough.
-* page_pool_create(): Create a pool.
- * flags: PP_FLAG_DMA_MAP, PP_FLAG_DMA_SYNC_DEV
- * order: 2^order pages on allocation
- * pool_size: size of the ptr_ring
- * nid: preferred NUMA node for allocation
- * dev: struct device. Used on DMA operations
- * dma_dir: DMA direction
- * max_len: max DMA sync memory size
- * offset: DMA address offset
+.. kernel-doc:: net/core/page_pool.c
+ :identifiers: page_pool_create
-* page_pool_put_page(): 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().
+.. kernel-doc:: include/net/page_pool.h
+ :identifiers: struct page_pool_params
-* page_pool_put_full_page(): Similar to page_pool_put_page(), but will DMA sync
- for the entire memory area configured in area pool->max_len.
+.. kernel-doc:: include/net/page_pool.h
+ :identifiers: page_pool_put_page page_pool_put_full_page
+ page_pool_recycle_direct page_pool_dev_alloc_pages
+ page_pool_get_dma_addr page_pool_get_dma_dir
-* page_pool_recycle_direct(): 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.
-
-* page_pool_dev_alloc_pages(): Get a page from the page allocator or page_pool
- caches.
-
-* page_pool_get_dma_addr(): Retrieve the stored DMA address.
-
-* page_pool_get_dma_dir(): Retrieve the stored DMA direction.
-
-* page_pool_put_page_bulk(): Tries to refill a number of pages into the
- ptr_ring cache holding ptr_ring producer lock. If the ptr_ring is full,
- page_pool_put_page_bulk() will release leftover pages to the page allocator.
- page_pool_put_page_bulk() is suitable to be run inside the driver NAPI tx
- completion loop for the XDP_REDIRECT use case.
- Please note the caller must not use data area after running
- page_pool_put_page_bulk(), as this function overwrites it.
-
-* page_pool_get_stats(): Retrieve statistics about the page_pool. This API
- is only available if the kernel has been configured with
- ``CONFIG_PAGE_POOL_STATS=y``. A pointer to a caller allocated ``struct
- page_pool_stats`` structure is passed to this API which is filled in. The
- caller can then report those stats to the user (perhaps via ethtool,
- debugfs, etc.). See below for an example usage of this API.
+.. kernel-doc:: net/core/page_pool.c
+ :identifiers: page_pool_put_page_bulk page_pool_get_stats
DMA sync
--------
@@ -146,36 +115,17 @@ with fragmented page pools.
Stats API and structures
------------------------
If the kernel is configured with ``CONFIG_PAGE_POOL_STATS=y``, the API
-``page_pool_get_stats()`` and structures described below are available. It
-takes a pointer to a ``struct page_pool`` and a pointer to a ``struct
-page_pool_stats`` allocated by the caller.
+page_pool_get_stats() and structures described below are available.
+It takes a pointer to a ``struct page_pool`` and a pointer to a struct
+page_pool_stats allocated by the caller.
-The API will fill in the provided ``struct page_pool_stats`` with
+The API will fill in the provided struct page_pool_stats with
statistics about the page_pool.
-The stats structure has the following fields::
-
- struct page_pool_stats {
- struct page_pool_alloc_stats alloc_stats;
- struct page_pool_recycle_stats recycle_stats;
- };
-
-
-The ``struct page_pool_alloc_stats`` has the following fields:
- * ``fast``: successful fast path allocations
- * ``slow``: slow path order-0 allocations
- * ``slow_high_order``: slow path high order allocations
- * ``empty``: ptr ring is empty, so a slow path allocation was forced.
- * ``refill``: an allocation which triggered a refill of the cache
- * ``waive``: pages obtained from the ptr ring that cannot be added to
- the cache due to a NUMA mismatch.
-
-The ``struct page_pool_recycle_stats`` has the following fields:
- * ``cached``: recycling placed page in the page pool cache
- * ``cache_full``: page pool cache was full
- * ``ring``: page placed into the ptr ring
- * ``ring_full``: page released from page pool because the ptr ring was full
- * ``released_refcnt``: page released (and not recycled) because refcnt > 1
+.. kernel-doc:: include/net/page_pool.h
+ :identifiers: struct page_pool_recycle_stats
+ struct page_pool_alloc_stats
+ struct page_pool_stats
Coding examples
===============
diff --git a/include/net/page_pool.h b/include/net/page_pool.h
index f1d5cc1fa13b..73d4f786418d 100644
--- a/include/net/page_pool.h
+++ b/include/net/page_pool.h
@@ -70,47 +70,76 @@ struct pp_alloc_cache {
struct page *cache[PP_ALLOC_CACHE_SIZE];
};
+/**
+ * struct page_pool_params - page pool parameters
+ * @flags: PP_FLAG_DMA_MAP, PP_FLAG_DMA_SYNC_DEV, PP_FLAG_PAGE_FRAG
+ * @order: 2^order pages on allocation
+ * @pool_size: size of the ptr_ring
+ * @nid: NUMA node id to allocate from pages from
+ * @dev: device, for DMA pre-mapping purposes
+ * @napi: NAPI which is the sole consumer of pages, otherwise NULL
+ * @dma_dir: DMA mapping direction
+ * @max_len: max DMA sync memory size for PP_FLAG_DMA_SYNC_DEV
+ * @offset: DMA sync address offset for PP_FLAG_DMA_SYNC_DEV
+ */
struct page_pool_params {
unsigned int flags;
unsigned int order;
unsigned int pool_size;
- int nid; /* Numa node id to allocate from pages from */
- struct device *dev; /* device, for DMA pre-mapping purposes */
- struct napi_struct *napi; /* Sole consumer of pages, otherwise NULL */
- enum dma_data_direction dma_dir; /* DMA mapping direction */
- unsigned int max_len; /* max DMA sync memory size */
- unsigned int offset; /* DMA addr offset */
+ int nid;
+ struct device *dev;
+ struct napi_struct *napi;
+ enum dma_data_direction dma_dir;
+ unsigned int max_len;
+ unsigned int offset;
+/* private: used by test code only */
void (*init_callback)(struct page *page, void *arg);
void *init_arg;
};
#ifdef CONFIG_PAGE_POOL_STATS
+/**
+ * struct page_pool_alloc_stats - allocation statistics
+ * @fast: successful fast path allocations
+ * @slow: slow path order-0 allocations
+ * @slow_high_order: slow path high order allocations
+ * @empty: ptr ring is empty, so a slow path allocation was forced
+ * @refill: an allocation which triggered a refill of the cache
+ * @waive: pages obtained from the ptr ring that cannot be added to
+ * the cache due to a NUMA mismatch
+ */
struct page_pool_alloc_stats {
- u64 fast; /* fast path allocations */
- u64 slow; /* slow-path order 0 allocations */
- u64 slow_high_order; /* slow-path high order allocations */
- u64 empty; /* failed refills due to empty ptr ring, forcing
- * slow path allocation
- */
- u64 refill; /* allocations via successful refill */
- u64 waive; /* failed refills due to numa zone mismatch */
+ u64 fast;
+ u64 slow;
+ u64 slow_high_order;
+ u64 empty;
+ u64 refill;
+ u64 waive;
};
+/**
+ * struct page_pool_recycle_stats - recycling (freeing) statistics
+ * @cached: recycling placed page in the page pool cache
+ * @cache_full: page pool cache was full
+ * @ring: page placed into the ptr ring
+ * @ring_full: page released from page pool because the ptr ring was full
+ * @released_refcnt: page released (and not recycled) because refcnt > 1
+ */
struct page_pool_recycle_stats {
- u64 cached; /* recycling placed page in the cache. */
- u64 cache_full; /* cache was full */
- u64 ring; /* recycling placed page back into ptr ring */
- u64 ring_full; /* page was released from page-pool because
- * PTR ring was full.
- */
- u64 released_refcnt; /* page released because of elevated
- * refcnt
- */
+ u64 cached;
+ u64 cache_full;
+ u64 ring;
+ u64 ring_full;
+ u64 released_refcnt;
};
-/* This struct wraps the above stats structs so users of the
- * page_pool_get_stats API can pass a single argument when requesting the
- * stats for the page pool.
+/**
+ * struct page_pool_stats - combined page pool use statistics
+ * @alloc_stats: see struct page_pool_alloc_stats
+ * @recycle_stats: see struct page_pool_recycle_stats
+ *
+ * Wrapper struct for combining page pool stats with different storage
+ * requirements.
*/
struct page_pool_stats {
struct page_pool_alloc_stats alloc_stats;
@@ -211,6 +240,12 @@ struct page_pool {
struct page *page_pool_alloc_pages(struct page_pool *pool, gfp_t gfp);
+/**
+ * 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);
@@ -230,8 +265,12 @@ static inline struct page *page_pool_dev_alloc_frag(struct page_pool *pool,
return page_pool_alloc_frag(pool, offset, size, gfp);
}
-/* get the stored dma direction. A driver might decide to treat this locally and
- * avoid the extra cache line from page_pool to determine the direction
+/**
+ * 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)
@@ -321,6 +360,19 @@ static inline bool page_pool_is_last_frag(struct page_pool *pool,
(page_pool_defrag_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,
@@ -337,14 +389,29 @@ static inline void page_pool_put_page(struct page_pool *pool,
#endif
}
-/* Same as above but will try to sync the entire area pool->max_len */
+/**
+ * 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);
}
-/* Same as above but the caller must guarantee safe context. e.g NAPI */
+/**
+ * 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)
{
@@ -354,6 +421,13 @@ static inline void page_pool_recycle_direct(struct page_pool *pool,
#define PAGE_POOL_DMA_USE_PP_FRAG_COUNT \
(sizeof(dma_addr_t) > sizeof(unsigned long))
+/**
+ * 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;
diff --git a/net/core/page_pool.c b/net/core/page_pool.c
index 8704127646b3..b3e8ed5241ea 100644
--- a/net/core/page_pool.c
+++ b/net/core/page_pool.c
@@ -58,6 +58,17 @@ static const char pp_stats[][ETH_GSTRING_LEN] = {
"rx_pp_recycle_released_ref",
};
+/**
+ * page_pool_get_stats() - fetch page pool stats
+ * @pool: pool from which page was allocated
+ * @stats: struct page_pool_stats to fill in
+ *
+ * Retrieve statistics about the page_pool. This API is only available
+ * if the kernel has been configured with ``CONFIG_PAGE_POOL_STATS=y``.
+ * A pointer to a caller allocated struct page_pool_stats structure
+ * is passed to this API which is filled in. The caller can then report
+ * those stats to the user (perhaps via ethtool, debugfs, etc.).
+ */
bool page_pool_get_stats(struct page_pool *pool,
struct page_pool_stats *stats)
{
@@ -224,6 +235,10 @@ static int page_pool_init(struct page_pool *pool,
return 0;
}
+/**
+ * page_pool_create() - create a page pool.
+ * @params: parameters, see struct page_pool_params
+ */
struct page_pool *page_pool_create(const struct page_pool_params *params)
{
struct page_pool *pool;
@@ -628,7 +643,21 @@ void page_pool_put_defragged_page(struct page_pool *pool, struct page *page,
}
EXPORT_SYMBOL(page_pool_put_defragged_page);
-/* Caller must not use data area after call, as this function overwrites it */
+/**
+ * page_pool_put_page_bulk() - release references on multiple pages
+ * @pool: pool from which pages were allocated
+ * @data: array holding page pointers
+ * @count: number of pages in @data
+ *
+ * Tries to refill a number of pages into the ptr_ring cache holding ptr_ring
+ * producer lock. If the ptr_ring is full, page_pool_put_page_bulk()
+ * will release leftover pages to the page allocator.
+ * page_pool_put_page_bulk() is suitable to be run inside the driver NAPI tx
+ * completion loop for the XDP_REDIRECT use case.
+ *
+ * Please note the caller must not use data area after running
+ * page_pool_put_page_bulk(), as this function overwrites it.
+ */
void page_pool_put_page_bulk(struct page_pool *pool, void **data,
int count)
{
--
2.41.0
