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

[Greg Kroah-Hartman]

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

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

From: Bart Van Assche <bart.vanassche@xxxxxxxxxxx>

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@xxxxxxxxxxx>
Reviewed-by: Hannes Reinecke <hare@xxxxxxxx>
Cc: Christoph Hellwig <hch@xxxxxx>
Signed-off-by: Mike Snitzer <snitzer@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 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;
 	}