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block: Do a full clone when splitting discard bios

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This fixes a data corruption bug when using discard on top of MD linear,
raid0 and raid10 personalities.

Commit 20d0189b10 "block: Introduce new bio_split()" permits sharing
the bio_vec between the two resulting bios. That is fine for read/write
requests where the bio_vec is immutable. For discards, however, we need
to be able to attach a payload and update the bio_vec so the page can
get mapped to a scatterlist entry. Therefore the bio_vec can not be
shared when splitting discards and we must do a full clone.

Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Reported-by: Seunguk Shin <seunguk.shin@samsung.com>
Tested-by: Seunguk Shin <seunguk.shin@samsung.com>
Cc: Seunguk Shin <seunguk.shin@samsung.com>
Cc: Jens Axboe <axboe@fb.com>
Cc: Kent Overstreet <kent.overstreet@gmail.com>
Cc: <stable@vger.kernel.org> # v3.14+
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@fb.com>
This commit is contained in:
Martin K. Petersen 2015-07-22 07:57:12 -04:00 committed by Jens Axboe
parent 5aa2a96b34
commit f3f5da624e
1 changed files with 12 additions and 3 deletions
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15
block/bio.c
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@ -1831,8 +1831,9 @@ EXPORT_SYMBOL(bio_endio);
* Allocates and returns a new bio which represents @sectors from the start of
* @bio, and updates @bio to represent the remaining sectors.
*
* The newly allocated bio will point to @bio's bi_io_vec; it is the caller's
* responsibility to ensure that @bio is not freed before the split.
* Unless this is a discard request the newly allocated bio will point
* to @bio's bi_io_vec; it is the caller's responsibility to ensure that
* @bio is not freed before the split.
*/
struct bio *bio_split(struct bio *bio, int sectors,
gfp_t gfp, struct bio_set *bs)
@ -1842,7 +1843,15 @@ struct bio *bio_split(struct bio *bio, int sectors,
BUG_ON(sectors <= 0);
BUG_ON(sectors >= bio_sectors(bio));
split = bio_clone_fast(bio, gfp, bs);
/*
* Discards need a mutable bio_vec to accommodate the payload
* required by the DSM TRIM and UNMAP commands.
*/
if (bio->bi_rw & REQ_DISCARD)
split = bio_clone_bioset(bio, gfp, bs);
else
split = bio_clone_fast(bio, gfp, bs);
if (!split)
return NULL;