NFSD: Don't start lockd when only NFSv4 is running

When starting without nfsv2 and nfsv3, nfsd does not need to start
lockd (and certainly doesn't need to fail because lockd failed to
register with the portmapper).
Reported-by: Gareth Williams <gareth@garethwilliams.me.uk>
Reviewed-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Kinglong Mee <kinglongmee@gmail.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>

fs/nfsd/netns.h

@@ -95,6 +95,7 @@ struct nfsd_net {
 	time_t nfsd4_grace;
 
 	bool nfsd_net_up;
+	bool lockd_up;
 
 	/*
 	 * Time of server startup

fs/nfsd/nfssvc.c

@@ -241,6 +241,11 @@ static void nfsd_shutdown_generic(void)
 	nfsd_racache_shutdown();
 }
 
+static bool nfsd_needs_lockd(void)
+{
+	return (nfsd_versions[2] != NULL) || (nfsd_versions[3] != NULL);
+}
+
 static int nfsd_startup_net(int nrservs, struct net *net)
 {
 	struct nfsd_net *nn = net_generic(net, nfsd_net_id);
@@ -255,9 +260,14 @@ static int nfsd_startup_net(int nrservs, struct net *net)
 	ret = nfsd_init_socks(net);
 	if (ret)
 		goto out_socks;
-	ret = lockd_up(net);
-	if (ret)
-		goto out_socks;
+
+	if (nfsd_needs_lockd() && !nn->lockd_up) {
+		ret = lockd_up(net);
+		if (ret)
+			goto out_socks;
+		nn->lockd_up = 1;
+	}
+
 	ret = nfs4_state_start_net(net);
 	if (ret)
 		goto out_lockd;
@@ -266,7 +276,10 @@ static int nfsd_startup_net(int nrservs, struct net *net)
 	return 0;
 
 out_lockd:
-	lockd_down(net);
+	if (nn->lockd_up) {
+		lockd_down(net);
+		nn->lockd_up = 0;
+	}
 out_socks:
 	nfsd_shutdown_generic();
 	return ret;
@@ -277,7 +290,10 @@ static void nfsd_shutdown_net(struct net *net)
 	struct nfsd_net *nn = net_generic(net, nfsd_net_id);
 
 	nfs4_state_shutdown_net(net);
-	lockd_down(net);
+	if (nn->lockd_up) {
+		lockd_down(net);
+		nn->lockd_up = 0;
+	}
 	nn->nfsd_net_up = false;
 	nfsd_shutdown_generic();
 }