[PATCH] md: fix bug where new drives added to an md array sometimes don't sync properly

This fixes a bug introduced in 2.6.18.

If a drive is added to a raid1 using older tools (mdadm-1.x or raidtools)
then it will be included in the array without any resync happening.

It has been submitted for 2.6.18.1.
Signed-off-by: Neil Brown <neilb@suse.de>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

drivers/md/md.c

@@ -3849,6 +3849,7 @@ static int hot_add_disk(mddev_t * mddev, dev_t dev)
 	}
 	clear_bit(In_sync, &rdev->flags);
 	rdev->desc_nr = -1;
+	rdev->saved_raid_disk = -1;
 	err = bind_rdev_to_array(rdev, mddev);
 	if (err)
 		goto abort_export;