SUNRPC: RPC client should retry with different versions of rpcbind

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

fs/Kconfig

@@ -1734,6 +1734,18 @@ config SUNRPC
 config SUNRPC_GSS
 	tristate
 
+config SUNRPC_BIND34
+	bool "Support for rpcbind versions 3 & 4 (EXPERIMENTAL)"
+	depends on SUNRPC && EXPERIMENTAL
+	help
+	  Provides kernel support for querying rpcbind servers via versions 3
+	  and 4 of the rpcbind protocol.  The kernel automatically falls back
+	  to version 2 if a remote rpcbind service does not support versions
+	  3 or 4.
+
+	  If unsure, say N to get traditional behavior (version 2 rpcbind
+	  requests only).
+
 config RPCSEC_GSS_KRB5
 	tristate "Secure RPC: Kerberos V mechanism (EXPERIMENTAL)"
 	depends on SUNRPC && EXPERIMENTAL

net/sunrpc/clnt.c

@@ -902,9 +902,11 @@ call_bind_status(struct rpc_task *task)
 				task->tk_pid);
 		break;
 	case -EPROTONOSUPPORT:
-		dprintk("RPC: %5u remote rpcbind version 2 unavailable\n",
+		dprintk("RPC: %5u remote rpcbind version unavailable, retrying\n",
 				task->tk_pid);
-		break;
+		task->tk_status = 0;
+		task->tk_action = call_bind;
+		return;
 	default:
 		dprintk("RPC: %5u unrecognized rpcbind error (%d)\n",
 				task->tk_pid, -task->tk_status);