From: Bart Van Assche <bart.vanassche@sandisk.com>
Date: Thu, 27 Apr 2017 17:11:16 +0000 (-0700)
Subject: dm mpath: delay requeuing while path initialization is in progress
X-Git-Tag: v4.12-rc1~120^2~10
X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=c1d7ecf7ca11d0edd3085262c8597203440d056c;p=platform%2Fkernel%2Flinux-exynos.git

dm mpath: delay requeuing while path initialization is in progress

Requeuing a request immediately while path initialization is ongoing
causes high CPU usage, something that is undesired.  Hence delay
requeuing while path initialization is in progress.

Signed-off-by: Bart Van Assche <bart.vanassche@sandisk.com>
Reviewed-by: Hannes Reinecke <hare@suse.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: <stable@vger.kernel.org>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
---

diff --git a/drivers/md/dm-mpath.c b/drivers/md/dm-mpath.c
index f3c79f1..d85baff 100644
--- a/drivers/md/dm-mpath.c
+++ b/drivers/md/dm-mpath.c
@@ -322,13 +322,16 @@ static int __pg_init_all_paths(struct multipath *m)
 	return atomic_read(&m->pg_init_in_progress);
 }
 
-static void pg_init_all_paths(struct multipath *m)
+static int pg_init_all_paths(struct multipath *m)
 {
+	int ret;
 	unsigned long flags;
 
 	spin_lock_irqsave(&m->lock, flags);
-	__pg_init_all_paths(m);
+	ret = __pg_init_all_paths(m);
 	spin_unlock_irqrestore(&m->lock, flags);
+
+	return ret;
 }
 
 static void __switch_pg(struct multipath *m, struct priority_group *pg)
@@ -503,7 +506,8 @@ static int multipath_clone_and_map(struct dm_target *ti, struct request *rq,
 		return -EIO;	/* Failed */
 	} else if (test_bit(MPATHF_QUEUE_IO, &m->flags) ||
 		   test_bit(MPATHF_PG_INIT_REQUIRED, &m->flags)) {
-		pg_init_all_paths(m);
+		if (pg_init_all_paths(m))
+			return DM_MAPIO_DELAY_REQUEUE;
 		return DM_MAPIO_REQUEUE;
 	}