From: Shaohua Li <shli@xxxxxx> This patch has been added to the 3.18 stable tree. If you have any objections, please let us know. =============== [ Upstream commit 9c573de3283af007ea11c17bde1e4568d9417328 ] 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@xxxxxxxxx> Fixes: 6ac45aeb6bca(block: avoid to merge splitted bio) Cc: stable@xxxxxxxxxxxxxxx (v4.3+) Cc: Ming Lei <ming.lei@xxxxxxxxxxxxx> Cc: Neil Brown <neilb@xxxxxxx> Reviewed-by: Jens Axboe <axboe@xxxxxx> Signed-off-by: Shaohua Li <shli@xxxxxx> Signed-off-by: Sasha Levin <sasha.levin@xxxxxxxxxx> --- drivers/md/md.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/drivers/md/md.c b/drivers/md/md.c index 6c169f1..3d2cc74 100644 --- a/drivers/md/md.c +++ b/drivers/md/md.c @@ -282,6 +282,8 @@ static void 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(); -- 2.5.0 -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html