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 f3c79f18874796d0d7fc8310f6ec49deaf8d2660..d85baffa33777d2170383a71ca7e519bd55a82c5 100644 (file)
--- 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;
        }