drbd: Disallow the peer_disk_state to be D_OUTDATED while connected

Signed-off-by: Philipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: Lars Ellenberg <lars.ellenberg@linbit.com>

drivers/block/drbd/drbd_main.c

@@ -745,6 +745,9 @@ is_valid_state(struct drbd_conf *mdev, union drbd_state ns)
 		  mdev->agreed_pro_version < 88)
 		rv = SS_NOT_SUPPORTED;
 
+	else if (ns.conn >= C_CONNECTED && ns.pdsk == D_UNKNOWN)
+		rv = SS_CONNECTED_OUTDATES;
+
 	return rv;
 }