Commit f00b16ad authored by Heinz Mauelshagen's avatar Heinz Mauelshagen Committed by Linus Torvalds
Browse files

[PATCH] dm io: fix bi_max_vecs 



The existing code allocates an extra slot in bi_io_vec[] and uses it to store
the region number.

This patch hides the extra slot from bio_add_page() so the region number can't
get overwritten.

Also remove a hard-coded SECTOR_SHIFT and fix a typo in a comment.

Signed-off-by: default avatarHeinz Mauelshagen <hjm@redhat.com>
Signed-off-by: default avatarAlasdair G Kergon <agk@redhat.com>
Cc: Milan Broz <mbroz@redhat.com>
Cc: dm-devel@redhat.com
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent 5cd307c5

drivers/md/dm-io.c

+9 −6
Original line number Diff line number Diff line
@@ -92,12 +92,12 @@ void dm_io_put(unsigned int num_pages) 
 *---------------------------------------------------------------*/

static inline void bio_set_region(struct bio *bio, unsigned region)

{

	bio->bi_io_vec[bio->bi_max_vecs - 1].bv_len = region;

	bio->bi_io_vec[bio->bi_max_vecs].bv_len = region;

}



static inline unsigned bio_get_region(struct bio *bio)

{

	return bio->bi_io_vec[bio->bi_max_vecs - 1].bv_len;

	return bio->bi_io_vec[bio->bi_max_vecs].bv_len;

}



/*-----------------------------------------------------------------
@@ -136,6 +136,7 @@ static int endio(struct bio *bio, unsigned int done, int error) 
		zero_fill_bio(bio);



	dec_count(io, bio_get_region(bio), error);

	bio->bi_max_vecs++;

	bio_put(bio);



	return 0;
@@ -250,16 +251,18 @@ static void do_region(int rw, unsigned int region, struct io_region *where, 


	while (remaining) {

		/*

		 * Allocate a suitably sized bio, we add an extra

		 * bvec for bio_get/set_region().

		 * Allocate a suitably sized-bio: we add an extra

		 * bvec for bio_get/set_region() and decrement bi_max_vecs

		 * to hide it from bio_add_page().

		 */

		num_bvecs = (remaining / (PAGE_SIZE >> 9)) + 2;

		num_bvecs = (remaining / (PAGE_SIZE >> SECTOR_SHIFT)) + 2;

		bio = bio_alloc_bioset(GFP_NOIO, num_bvecs, _bios);

		bio->bi_sector = where->sector + (where->count - remaining);

		bio->bi_bdev = where->bdev;

		bio->bi_end_io = endio;

		bio->bi_private = io;

		bio->bi_destructor = dm_bio_destructor;

		bio->bi_max_vecs--;

		bio_set_region(bio, region);



		/*
@@ -302,7 +305,7 @@ static void dispatch_io(int rw, unsigned int num_regions, 
	}



	/*

	 * Drop the extra refence that we were holding to avoid

	 * Drop the extra reference that we were holding to avoid

	 * the io being completed too early.

	 */

	dec_count(io, 0, 0);

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