SUNRPC/NFSD: Support a new option for ignoring the result of svc_register

NFSv4 clients can contact port 2049 directly instead of needing the
portmapper.

Therefore a failure to register to the portmapper when starting an
NFSv4-only server isn't really a problem.

But Gareth Williams reports that an attempt to start an NFSv4-only
server without starting portmap fails:

#rpc.nfsd -N 2 -N 3
rpc.nfsd: writing fd to kernel failed: errno 111 (Connection refused)
rpc.nfsd: unable to set any sockets for nfsd

Add a flag to svc_version to tell the rpc layer it can safely ignore an
rpcbind failure in the NFSv4-only case.

Reported-by: Gareth Williams <[e-mail]>
Reviewed-by: Chuck Lever <[e-mail]>
Signed-off-by: Kinglong Mee <[e-mail]>
Signed-off-by: J. Bruce Fields <[e-mail]>

fs/nfsd/nfs4proc.c

···
 		.vs_proc	= nfsd_procedures4,
 		.vs_dispatch	= nfsd_dispatch,
 		.vs_xdrsize	= NFS4_SVC_XDRSIZE,
+		.vs_rpcb_optnl	= 1,
 };
 
 /*

include/linux/sunrpc/svc.h

···
 	struct svc_procedure *	vs_proc;	/* per-procedure info */
 	u32			vs_xdrsize;	/* xdrsize needed for this version */
 
-	unsigned int		vs_hidden : 1;	/* Don't register with portmapper.
+	unsigned int		vs_hidden : 1,	/* Don't register with portmapper.
 						 * Only used for nfsacl so far. */
+				vs_rpcb_optnl:1;/* Don't care the result of register.
+						 * Only used for nfsv4. */
 
 	/* Override dispatch function (e.g. when caching replies).
 	 * A return value of 0 means drop the request. 

net/sunrpc/svc.c

···
 #endif
 	}
 
-	if (error < 0)
-		printk(KERN_WARNING "svc: failed to register %sv%u RPC "
-			"service (errno %d).\n", progname, version, -error);
 	return error;
 }
 
···
 		 const unsigned short port)
 {
 	struct svc_program	*progp;
+	struct svc_version	*vers;
 	unsigned int		i;
 	int			error = 0;
 
···
 
 	for (progp = serv->sv_program; progp; progp = progp->pg_next) {
 		for (i = 0; i < progp->pg_nvers; i++) {
-			if (progp->pg_vers[i] == NULL)
+			vers = progp->pg_vers[i];
+			if (vers == NULL)
 				continue;
 
 			dprintk("svc: svc_register(%sv%d, %s, %u, %u)%s\n",
···
 					proto == IPPROTO_UDP?  "udp" : "tcp",
 					port,
 					family,
-					progp->pg_vers[i]->vs_hidden?
-						" (but not telling portmap)" : "");
+					vers->vs_hidden ?
+					" (but not telling portmap)" : "");
 
-			if (progp->pg_vers[i]->vs_hidden)
+			if (vers->vs_hidden)
 				continue;
 
 			error = __svc_register(net, progp->pg_name, progp->pg_prog,
 						i, family, proto, port);
-			if (error < 0)
+
+			if (vers->vs_rpcb_optnl) {
+				error = 0;
+				continue;
+			}
+
+			if (error < 0) {
+				printk(KERN_WARNING "svc: failed to register "
+					"%sv%u RPC service (errno %d).\n",
+					progp->pg_name, i, -error);
 				break;
+			}
 		}
 	}