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| author |   Ming Lei <ming.lei@redhat.com> | 2018-01-11 14:01:56 +0800 |
|---|---|---|
| committer |   Mike Snitzer <snitzer@redhat.com> | 2018-01-17 09:16:17 -0500 |
| commit | 050af08ffb1b62af69196d61c22a0755f9a3cdbd (patch) | |
| tree | ecb7779a5e70a907d74fd1134cd8d5dc7ab617cf /drivers/md/dm-mpath.c | |
| parent | dm log writes: fix max length used for kstrndup (diff) | |
| download | linux-dev-050af08ffb1b62af69196d61c22a0755f9a3cdbd.tar.xz linux-dev-050af08ffb1b62af69196d61c22a0755f9a3cdbd.zip | |
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.c | 14 |
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; |