Commit 9c573de3 authored Apr 25, 2016 by Shaohua Li

MD: make bio mergeable

blk_queue_split marks bio unmergeable, which makes sense for normal bio.
But if dispatching the bio to underlayer disk, the blk_queue_split
checks are invalid, hence it's possible the bio becomes mergeable.

In the reported bug, this bug causes trim against raid0 performance slash
https://bugzilla.kernel.org/show_bug.cgi?id=117051



Reported-and-tested-by: Park Ju Hyung <qkrwngud825@gmail.com>
Fixes: 6ac45aeb(block: avoid to merge splitted bio)
Cc: stable@vger.kernel.org (v4.3+)
Cc: Ming Lei <ming.lei@canonical.com>
Cc: Neil Brown <neilb@suse.de>
Reviewed-by: Jens Axboe <axboe@fb.com>
Signed-off-by: Shaohua Li <shli@fb.com>

parent b297874a

drivers/md/md.c

+2 −0

Original line number	Diff line number	Diff line
		@@ -284,6 +284,8 @@ static blk_qc_t md_make_request(struct request_queue q, struct bio bio)
		* go away inside make_request
		*/
		sectors = bio_sectors(bio);
		/* bio could be mergeable after passing to underlayer */
		bio->bi_rw &= ~REQ_NOMERGE;
		mddev->pers->make_request(mddev, bio);

		cpu = part_stat_lock();

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