lockd: Try to reconnect if statd has moved

commit 173b3afc upstream.

If rpc.statd is restarted, upcalls to monitor hosts can fail with
ECONNREFUSED.  In that case force a lookup of statd's new port and retry the
upcall.
Signed-off-by: Benjamin Coddington <bcodding@redhat.com>
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
[bwh: Backported to 3.2: not using RPC_TASK_SOFTCONN]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

fs/lockd/mon.c

@@ -111,6 +111,12 @@ static int nsm_mon_unmon(struct nsm_handle *nsm, u32 proc, struct nsm_res *res)
 
 	msg.rpc_proc = &clnt->cl_procinfo[proc];
 	status = rpc_call_sync(clnt, &msg, 0);
+	if (status == -ECONNREFUSED) {
+		dprintk("lockd:	NSM upcall RPC failed, status=%d, forcing rebind\n",
+				status);
+		rpc_force_rebind(clnt);
+		status = rpc_call_sync(clnt, &msg, 0);
+	}
 	if (status < 0)
 		dprintk("lockd: NSM upcall RPC failed, status=%d\n",
 				status);