lkml.org 
[lkml]   [2018]   [Apr]   [25]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH 4.14 047/183] dm mpath: return DM_MAPIO_REQUEUE on blk-mq rq allocation failure
Date
4.14-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Ming Lei <ming.lei@redhat.com>


[ 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 <ming.lei@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/md/dm-mpath.c | 14 +++++++++++++-
1 file changed, 13 insertions(+), 1 deletion(-)

--- a/drivers/md/dm-mpath.c
+++ b/drivers/md/dm-mpath.c
@@ -502,8 +502,20 @@ static int multipath_clone_and_map(struc
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;

\
 
 \ /
  Last update: 2018-04-25 13:26    [W:0.761 / U:13.060 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site