[PATCH 002 of 9] md: Skip all metadata update processing when using external metadata.

[NeilBrown <neilb@suse.de>]

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>

### Diffstat output
 ./drivers/md/md.c |    2 ++
 1 file changed, 2 insertions(+)

diff .prev/drivers/md/md.c ./drivers/md/md.c
--- .prev/drivers/md/md.c	2008-04-29 12:27:55.000000000 +1000
+++ ./drivers/md/md.c	2008-04-29 12:27:56.000000000 +1000
@@ -1651,6 +1651,8 @@ static void md_update_sb(mddev_t * mddev
 	int sync_req;
 	int nospares = 0;
 
+	if (mddev->external)
+		return;
 repeat:
 	spin_lock_irq(&mddev->write_lock);