linux-kernel - [PATCH 4.11 030/197] dm mpath: delay requeuing while path initialization is in progress

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Date:   Tue, 23 May 2017 22:06:31 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        Bart Van Assche <bart.vanassche@...disk.com>,
        Hannes Reinecke <hare@...e.com>,
        Christoph Hellwig <hch@....de>,
        Mike Snitzer <snitzer@...hat.com>
Subject: [PATCH 4.11 030/197] dm mpath: delay requeuing while path initialization is in progress

4.11-stable review patch.  If anyone has any objections, please let me know.

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

From: Bart Van Assche <bart.vanassche@...disk.com>

commit c1d7ecf7ca11d0edd3085262c8597203440d056c upstream.

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@...disk.com>
Reviewed-by: Hannes Reinecke <hare@...e.com>
Cc: Christoph Hellwig <hch@....de>
Signed-off-by: Mike Snitzer <snitzer@...hat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/md/dm-mpath.c |   10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

--- a/drivers/md/dm-mpath.c
+++ b/drivers/md/dm-mpath.c
@@ -322,13 +322,16 @@ static int __pg_init_all_paths(struct mu
 	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(struc
 		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;
 	}