From: Ming Lei Date: Thu, 11 Jan 2018 06:01:56 +0000 (+0800) Subject: dm mpath: return DM_MAPIO_REQUEUE on blk-mq rq allocation failure X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=2e102fe86ede237ca875da9336648caa5e2fcac6;p=GitHub%2FLineageOS%2Fandroid_kernel_motorola_exynos9610.git dm mpath: return DM_MAPIO_REQUEUE on blk-mq rq allocation failure [ Upstream commit 050af08ffb1b62af69196d61c22a0755f9a3cdbd ] blk-mq will rerun queue via RESTART or dispatch wake after one request is completed, so not necessary to wait random time for requeuing, we should trust blk-mq to do it. More importantly, we need to return BLK_STS_RESOURCE to blk-mq so that dequeuing from the I/O scheduler can be stopped, this results in improved I/O merging. Signed-off-by: Ming Lei Signed-off-by: Mike Snitzer Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman --- diff --git a/drivers/md/dm-mpath.c b/drivers/md/dm-mpath.c index 2704a55f8b6e..8b7328666eaa 100644 --- a/drivers/md/dm-mpath.c +++ b/drivers/md/dm-mpath.c @@ -502,8 +502,20 @@ static int multipath_clone_and_map(struct dm_target *ti, struct request *rq, if (queue_dying) { atomic_inc(&m->pg_init_in_progress); activate_or_offline_path(pgpath); + return DM_MAPIO_DELAY_REQUEUE; } - return DM_MAPIO_DELAY_REQUEUE; + + /* + * blk-mq's SCHED_RESTART can cover this requeue, so we + * needn't deal with it by DELAY_REQUEUE. More importantly, + * we have to return DM_MAPIO_REQUEUE so that blk-mq can + * get the queue busy feedback (via BLK_STS_RESOURCE), + * otherwise I/O merging can suffer. + */ + if (q->mq_ops) + return DM_MAPIO_REQUEUE; + else + return DM_MAPIO_DELAY_REQUEUE; } clone->bio = clone->biotail = NULL; clone->rq_disk = bdev->bd_disk;