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block: Document the bio_vec properties

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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 <bvanassche@acm.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
CC: Christoph Hellwig <hch@infradead.org>
Cc: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Bart Van Assche 2020-05-18 21:07:36 -07:00 committed by Jens Axboe
parent c1527c0e12
commit 854b5f01dc
1 changed files with 11 additions and 2 deletions
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13
include/linux/bvec.h
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@ -12,8 +12,17 @@
#include <linux/errno.h>
#include <linux/mm.h>
/*
* 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;