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authorMing Lei <ming.lei@redhat.com>2018-01-11 09:01:56 +0300
committerMike Snitzer <snitzer@redhat.com>2018-01-17 17:16:17 +0300
commit050af08ffb1b62af69196d61c22a0755f9a3cdbd (patch)
treeecb7779a5e70a907d74fd1134cd8d5dc7ab617cf /drivers/md/dm-mpath.c
parent4b259fc4a8a12dcd0ffd670877a7a1ca2ab0f3e3 (diff)
downloadlinux-050af08ffb1b62af69196d61c22a0755f9a3cdbd.tar.xz
dm mpath: return DM_MAPIO_REQUEUE on blk-mq rq allocation failure
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 <ming.lei@redhat.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Diffstat (limited to 'drivers/md/dm-mpath.c')
-rw-r--r--drivers/md/dm-mpath.c14
1 files changed, 13 insertions, 1 deletions
diff --git a/drivers/md/dm-mpath.c b/drivers/md/dm-mpath.c
index be581765edd1..e0187798ccae 100644
--- a/drivers/md/dm-mpath.c
+++ b/drivers/md/dm-mpath.c
@@ -533,8 +533,20 @@ static int multipath_clone_and_map(struct dm_target *ti, struct request *rq,
if (blk_queue_dying(q)) {
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;