Commit d8166519 authored by Matthew Wilcox (Oracle)'s avatar Matthew Wilcox (Oracle) Committed by Jens Axboe
Browse files

block: Fix page_is_mergeable() for compound pages 



If we pass in an offset which is larger than PAGE_SIZE, then
page_is_mergeable() thinks it's not mergeable with the previous bio_vec,
leading to a large number of bio_vecs being used.  Use a slightly more
obvious test that the two pages are compatible with each other.

Fixes: 52d52d1c ("block: only allow contiguous page structs in a bio_vec")
Signed-off-by: default avatarMatthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: default avatarMing Lei <ming.lei@redhat.com>
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent af822aa6

block/bio.c

+5 −5
Original line number Diff line number Diff line
@@ -740,8 +740,8 @@ static inline bool page_is_mergeable(const struct bio_vec *bv, 
		struct page *page, unsigned int len, unsigned int off,

		bool *same_page)

{

	phys_addr_t vec_end_addr = page_to_phys(bv->bv_page) +

		bv->bv_offset + bv->bv_len - 1;

	size_t bv_end = bv->bv_offset + bv->bv_len;

	phys_addr_t vec_end_addr = page_to_phys(bv->bv_page) + bv_end - 1;

	phys_addr_t page_addr = page_to_phys(page);



	if (vec_end_addr + 1 != page_addr + off)
@@ -750,9 +750,9 @@ static inline bool page_is_mergeable(const struct bio_vec *bv, 
		return false;



	*same_page = ((vec_end_addr & PAGE_MASK) == page_addr);

	if (!*same_page && pfn_to_page(PFN_DOWN(vec_end_addr)) + 1 != page)

		return false;

	if (*same_page)

		return true;

	return (bv->bv_page + bv_end / PAGE_SIZE) == (page + off / PAGE_SIZE);

}



/*