From 854b5f01dc6a7b59f0dddd646a80b1fcd767a8db Mon Sep 17 00:00:00 2001 From: Bart Van Assche Date: Mon, 18 May 2020 21:07:36 -0700 Subject: [PATCH] block: Document the bio_vec properties Since it is nontrivial that nth_page() does not have to be used for a bio_vec, document this. Signed-off-by: Bart Van Assche Reviewed-by: Christoph Hellwig CC: Christoph Hellwig Cc: Ming Lei Signed-off-by: Jens Axboe --- include/linux/bvec.h | 13 +++++++++++-- 1 file changed, 11 insertions(+), 2 deletions(-) diff --git a/include/linux/bvec.h b/include/linux/bvec.h index a81c13ac1972..ac0c7299d5b8 100644 --- a/include/linux/bvec.h +++ b/include/linux/bvec.h @@ -12,8 +12,17 @@ #include #include -/* - * was unsigned short, but we might as well be ready for > 64kB I/O pages +/** + * struct bio_vec - a contiguous range of physical memory addresses + * @bv_page: First page associated with the address range. + * @bv_len: Number of bytes in the address range. + * @bv_offset: Start of the address range relative to the start of @bv_page. + * + * The following holds for a bvec if n * PAGE_SIZE < bv_offset + bv_len: + * + * nth_page(@bv_page, n) == @bv_page + n + * + * This holds because page_is_mergeable() checks the above property. */ struct bio_vec { struct page *bv_page;