SUNRPC: Refactor rpc_ping()

Make it use the rpc_null_call_helper() so that it can share the
new rpc_call_ops structure to be introduced in the next patch.
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>

net/sunrpc/clnt.c

@@ -2694,17 +2694,6 @@ static const struct rpc_procinfo rpcproc_null = {
 	.p_decode = rpcproc_decode_null,
 };
 
-static int rpc_ping(struct rpc_clnt *clnt)
-{
-	struct rpc_message msg = {
-		.rpc_proc = &rpcproc_null,
-	};
-	int err;
-	err = rpc_call_sync(clnt, &msg, RPC_TASK_SOFT | RPC_TASK_SOFTCONN |
-			    RPC_TASK_NULLCREDS);
-	return err;
-}
-
 static
 struct rpc_task *rpc_call_null_helper(struct rpc_clnt *clnt,
 		struct rpc_xprt *xprt, struct rpc_cred *cred, int flags,
@@ -2733,6 +2722,19 @@ struct rpc_task *rpc_call_null(struct rpc_clnt *clnt, struct rpc_cred *cred, int
 }
 EXPORT_SYMBOL_GPL(rpc_call_null);
 
+static int rpc_ping(struct rpc_clnt *clnt)
+{
+	struct rpc_task	*task;
+	int status;
+
+	task = rpc_call_null_helper(clnt, NULL, NULL, 0, NULL, NULL);
+	if (IS_ERR(task))
+		return PTR_ERR(task);
+	status = task->tk_status;
+	rpc_put_task(task);
+	return status;
+}
+
 struct rpc_cb_add_xprt_calldata {
 	struct rpc_xprt_switch *xps;
 	struct rpc_xprt *xprt;