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 <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>
diff --git a/include/linux/sunrpc/svc.h b/include/linux/sunrpc/svc.h
index b6316423..04e7632 100644
--- a/include/linux/sunrpc/svc.h
+++ b/include/linux/sunrpc/svc.h
@@ -386,8 +386,10 @@
 	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.