md: skip all metadata update processing when using external metadata.

All the metadata update processing for external metadata is on in user-space
or through the sysfs interfaces, so make "md_update_sb" a no-op in that case.

Signed-off-by: Neil Brown <neilb@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 2 insertions, 0 deletions

diff --git a/drivers/md/md.c b/drivers/md/md.c
index 11457a28a14c..61767f1962eb 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -1652,6 +1652,8 @@ static void md_update_sb(mddev_t * mddev, int force_change)
         int sync_req;
         int nospares = 0;
 
+        if (mddev->external)
+                return;
 repeat:
         spin_lock_irq(&mddev->write_lock);