SUNRPC: Add a new error code for retry waiting for another binder

Add new error code processing to the kernel's rpcbind client and to
call_bind_status() to distinguish two cases:

Case 1: the remote has replied that the program/version tuple is not
registered (returns -EACCES)

Case 2: another process is already in the middle of binding on this
transport (now returns -EAGAIN)

This change allows more specific retry processing for each of these two
cases.
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

net/sunrpc/clnt.c

@@ -950,6 +950,12 @@ call_bind_status(struct rpc_task *task)
 	}
 
 	switch (task->tk_status) {
+	case -EAGAIN:
+		dprintk("RPC: %5u rpcbind waiting for another request "
+				"to finish\n", task->tk_pid);
+		/* avoid busy-waiting here -- could be a network outage. */
+		rpc_delay(task, 5*HZ);
+		goto retry_timeout;
 	case -EACCES:
 		dprintk("RPC: %5u remote rpcbind: RPC program/version "
 				"unavailable\n", task->tk_pid);

net/sunrpc/rpcb_clnt.c

@@ -341,7 +341,7 @@ void rpcb_getport_async(struct rpc_task *task)
 	BUG_ON(clnt->cl_parent != clnt);
 
 	if (xprt_test_and_set_binding(xprt)) {
-		status = -EACCES;		/* tell caller to check again */
+		status = -EAGAIN;	/* tell caller to check again */
 		dprintk("RPC: %5u %s: waiting for another binder\n",
 			task->tk_pid, __FUNCTION__);
 		goto bailout_nowake;