Currently page_pool_alloc_frag() is not supported in 32-bit arch with 64-bit DMA because of the overlap issue between pp_frag_count and dma_addr_upper in 'struct page' for those arches, which seems to be quite common, see [1], which means driver may need to handle it when using frag API. In order to simplify the driver's work when using frag API this patch allows page_pool_alloc_frag() to call page_pool_alloc_pages() to return pages for those arches. mlx5 calls page_pool_create() with PP_FLAG_PAGE_FRAG and is not using the frag API, and the PP_FLAG_PAGE_FRAG checking will now be removed in this patch, a new checking for the mlx5 driver is needed to retain the old behavior. As we have not come up with a better name yet, so PAGE_POOL_DMA_USE_PP_FRAG_COUNT is reused here. Note that it may aggravate truesize underestimate problem for skb as there is no page splitting for those pages, if driver need a accurate truesize, it may calculate that according to frag size, page order and PAGE_POOL_DMA_USE_PP_FRAG_COUNT being true or not. And we may provide a helper for that if it turns out to be helpful. 1. https://lore.kernel.org/all/20211117075652.58299-1-linyunsheng@xxxxxxxxxx/ Signed-off-by: Yunsheng Lin <linyunsheng@xxxxxxxxxx> CC: Lorenzo Bianconi <lorenzo@xxxxxxxxxx> CC: Alexander Duyck <alexander.duyck@xxxxxxxxx> CC: Liang Chen <liangchen.linux@xxxxxxxxx> CC: Alexander Lobakin <aleksander.lobakin@xxxxxxxxx> --- .../net/ethernet/mellanox/mlx5/core/en_main.c | 10 +++++ include/net/page_pool.h | 45 ++++++++++++++++--- net/core/page_pool.c | 18 ++------ 3 files changed, 52 insertions(+), 21 deletions(-) diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en_main.c b/drivers/net/ethernet/mellanox/mlx5/core/en_main.c index a7c526ee5024..42ccb77a1b6c 100644 --- a/drivers/net/ethernet/mellanox/mlx5/core/en_main.c +++ b/drivers/net/ethernet/mellanox/mlx5/core/en_main.c @@ -832,6 +832,16 @@ static int mlx5e_alloc_rq(struct mlx5e_params *params, /* Create a page_pool and register it with rxq */ struct page_pool_params pp_params = { 0 }; + /* Return error here to avoid mlx5e_page_release_fragmented() + * calling page_pool_defrag_page() to write to pp_frag_count + * which is overlapped with dma_addr_upper in 'struct page' for + * arch with PAGE_POOL_DMA_USE_PP_FRAG_COUNT being true. + */ + if (PAGE_POOL_DMA_USE_PP_FRAG_COUNT) { + err = -EINVAL; + goto err_free_by_rq_type; + } + pp_params.order = 0; pp_params.flags = PP_FLAG_DMA_MAP | PP_FLAG_DMA_SYNC_DEV | PP_FLAG_PAGE_FRAG; pp_params.pool_size = pool_size; diff --git a/include/net/page_pool.h b/include/net/page_pool.h index 126f9e294389..83bd13491105 100644 --- a/include/net/page_pool.h +++ b/include/net/page_pool.h @@ -32,7 +32,7 @@ #include <linux/mm.h> /* Needed by ptr_ring */ #include <linux/ptr_ring.h> -#include <linux/dma-direction.h> +#include <linux/dma-mapping.h> #define PP_FLAG_DMA_MAP BIT(0) /* Should page_pool do the DMA * map/unmap @@ -50,6 +50,9 @@ PP_FLAG_DMA_SYNC_DEV |\ PP_FLAG_PAGE_FRAG) +#define PAGE_POOL_DMA_USE_PP_FRAG_COUNT \ + (sizeof(dma_addr_t) > sizeof(unsigned long)) + /* * Fast allocation side cache array/stack * @@ -219,8 +222,33 @@ static inline struct page *page_pool_dev_alloc_pages(struct page_pool *pool) return page_pool_alloc_pages(pool, gfp); } -struct page *page_pool_alloc_frag(struct page_pool *pool, unsigned int *offset, - unsigned int size, gfp_t gfp); +struct page *__page_pool_alloc_frag(struct page_pool *pool, + unsigned int *offset, unsigned int size, + gfp_t gfp); + +static inline struct page *page_pool_alloc_frag(struct page_pool *pool, + unsigned int *offset, + unsigned int size, gfp_t gfp) +{ + unsigned int max_size = PAGE_SIZE << pool->p.order; + + size = ALIGN(size, dma_get_cache_alignment()); + + if (WARN_ON(!(pool->p.flags & PP_FLAG_PAGE_FRAG) || + size > max_size)) + return NULL; + + /* Don't allow page splitting and allocate one big frag + * for 32-bit arch with 64-bit DMA, corresponding to + * the checking in page_pool_is_last_frag(). + */ + if (PAGE_POOL_DMA_USE_PP_FRAG_COUNT) { + *offset = 0; + return page_pool_alloc_pages(pool, gfp); + } + + return __page_pool_alloc_frag(pool, offset, size, gfp); +} static inline struct page *page_pool_dev_alloc_frag(struct page_pool *pool, unsigned int *offset, @@ -322,8 +350,14 @@ static inline long page_pool_defrag_page(struct page *page, long nr) static inline bool page_pool_is_last_frag(struct page_pool *pool, struct page *page) { - /* If fragments aren't enabled or count is 0 we were the last user */ + /* We assume we are the last frag user that is still holding + * on to the page if: + * 1. Fragments aren't enabled. + * 2. We are running in 32-bit arch with 64-bit DMA. + * 3. page_pool_defrag_page() indicate we are the last user. + */ return !(pool->p.flags & PP_FLAG_PAGE_FRAG) || + PAGE_POOL_DMA_USE_PP_FRAG_COUNT || (page_pool_defrag_page(page, 1) == 0); } @@ -357,9 +391,6 @@ static inline void page_pool_recycle_direct(struct page_pool *pool, page_pool_put_full_page(pool, page, true); } -#define PAGE_POOL_DMA_USE_PP_FRAG_COUNT \ - (sizeof(dma_addr_t) > sizeof(unsigned long)) - 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 a3e12a61d456..9c4118c62997 100644 --- a/net/core/page_pool.c +++ b/net/core/page_pool.c @@ -14,7 +14,6 @@ #include <net/xdp.h> #include <linux/dma-direction.h> -#include <linux/dma-mapping.h> #include <linux/page-flags.h> #include <linux/mm.h> /* for put_page() */ #include <linux/poison.h> @@ -200,10 +199,6 @@ static int page_pool_init(struct page_pool *pool, */ } - if (PAGE_POOL_DMA_USE_PP_FRAG_COUNT && - pool->p.flags & PP_FLAG_PAGE_FRAG) - return -EINVAL; - #ifdef CONFIG_PAGE_POOL_STATS pool->recycle_stats = alloc_percpu(struct page_pool_recycle_stats); if (!pool->recycle_stats) @@ -715,18 +710,13 @@ static void page_pool_free_frag(struct page_pool *pool) page_pool_return_page(pool, page); } -struct page *page_pool_alloc_frag(struct page_pool *pool, - unsigned int *offset, - unsigned int size, gfp_t gfp) +struct page *__page_pool_alloc_frag(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 = pool->frag_page; - if (WARN_ON(!(pool->p.flags & PP_FLAG_PAGE_FRAG) || - size > max_size)) - return NULL; - - size = ALIGN(size, dma_get_cache_alignment()); *offset = pool->frag_offset; if (page && *offset + size > max_size) { @@ -759,7 +749,7 @@ struct page *page_pool_alloc_frag(struct page_pool *pool, alloc_stat_inc(pool, fast); return page; } -EXPORT_SYMBOL(page_pool_alloc_frag); +EXPORT_SYMBOL(__page_pool_alloc_frag); static void page_pool_empty_ring(struct page_pool *pool) { -- 2.33.0
