From b358e2122b9d7aa99f681d4edfafd999845d16ff Mon Sep 17 00:00:00 2001 From: Kevin Hao Date: Thu, 4 Feb 2021 18:56:35 +0800 Subject: [PATCH] mm: page_frag: Introduce page_frag_alloc_align() In the current implementation of page_frag_alloc(), it doesn't have any align guarantee for the returned buffer address. But for some hardwares they do require the DMA buffer to be aligned correctly, so we would have to use some workarounds like below if the buffers allocated by the page_frag_alloc() are used by these hardwares for DMA. buf = page_frag_alloc(really_needed_size + align); buf = PTR_ALIGN(buf, align); These codes seems ugly and would waste a lot of memories if the buffers are used in a network driver for the TX/RX. So introduce page_frag_alloc_align() to make sure that an aligned buffer address is returned. Signed-off-by: Kevin Hao Acked-by: Vlastimil Babka Reviewed-by: Alexander Duyck Signed-off-by: Jakub Kicinski --- include/linux/gfp.h | 12 ++++++++++-- mm/page_alloc.c | 8 +++++--- 2 files changed, 15 insertions(+), 5 deletions(-) diff --git a/include/linux/gfp.h b/include/linux/gfp.h index 6e479e9..80544d5 100644 --- a/include/linux/gfp.h +++ b/include/linux/gfp.h @@ -583,8 +583,16 @@ extern void free_pages(unsigned long addr, unsigned int order); struct page_frag_cache; extern void __page_frag_cache_drain(struct page *page, unsigned int count); -extern void *page_frag_alloc(struct page_frag_cache *nc, - unsigned int fragsz, gfp_t gfp_mask); +extern void *page_frag_alloc_align(struct page_frag_cache *nc, + unsigned int fragsz, gfp_t gfp_mask, + unsigned int align_mask); + +static inline void *page_frag_alloc(struct page_frag_cache *nc, + unsigned int fragsz, gfp_t gfp_mask) +{ + return page_frag_alloc_align(nc, fragsz, gfp_mask, ~0u); +} + extern void page_frag_free(void *addr); #define __free_page(page) __free_pages((page), 0) diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 519a60d..ef5070f 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -5137,8 +5137,9 @@ void __page_frag_cache_drain(struct page *page, unsigned int count) } EXPORT_SYMBOL(__page_frag_cache_drain); -void *page_frag_alloc(struct page_frag_cache *nc, - unsigned int fragsz, gfp_t gfp_mask) +void *page_frag_alloc_align(struct page_frag_cache *nc, + unsigned int fragsz, gfp_t gfp_mask, + unsigned int align_mask) { unsigned int size = PAGE_SIZE; struct page *page; @@ -5190,11 +5191,12 @@ refill: } nc->pagecnt_bias--; + offset &= align_mask; nc->offset = offset; return nc->va + offset; } -EXPORT_SYMBOL(page_frag_alloc); +EXPORT_SYMBOL(page_frag_alloc_align); /* * Frees a page fragment allocated out of either a compound or order 0 page. -- 2.7.4