metadata_update sends message to other nodes

   - request to send a message
   - make changes to superblock
   - send messages telling everyone that the superblock has changed
   - other nodes all read the superblock
   - other nodes all ack the messages
   - updating node release the "I'm sending a message" resource.

Signed-off-by: Goldwyn Rodrigues <rgoldwyn@suse.com>
diff --git a/drivers/md/md-cluster.h b/drivers/md/md-cluster.h
index 51a24df..658982a 100644
--- a/drivers/md/md-cluster.h
+++ b/drivers/md/md-cluster.h
@@ -12,6 +12,9 @@
 	int (*leave)(struct mddev *mddev);
 	int (*slot_number)(struct mddev *mddev);
 	void (*resync_info_update)(struct mddev *mddev, sector_t lo, sector_t hi);
+	int (*metadata_update_start)(struct mddev *mddev);
+	int (*metadata_update_finish)(struct mddev *mddev);
+	int (*metadata_update_cancel)(struct mddev *mddev);
 };
 
 #endif /* _MD_CLUSTER_H */