sunrpc: fix loss of task->tk_status after rpc_delay call in xprt_alloc_slot

xprt_alloc_slot will call rpc_delay() to make the task wait a bit before
retrying when it gets back an -ENOMEM error from xprt_dynamic_alloc_slot.
The problem is that rpc_delay will clear the task->tk_status, causing
call_reserveresult to abort the task.

The solution is simply to let call_reserveresult handle the ENOMEM error
directly.
Reported-by: Jeff Layton <jlayton@redhat.com>
Cc: stable@vger.kernel.org [>= 3.1]
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

net/sunrpc/clnt.c

@@ -1288,6 +1288,8 @@ call_reserveresult(struct rpc_task *task)
 	}
 
 	switch (status) {
+	case -ENOMEM:
+		rpc_delay(task, HZ >> 2);
 	case -EAGAIN:	/* woken up; retry */
 		task->tk_action = call_reserve;
 		return;

net/sunrpc/xprt.c

@@ -984,15 +984,16 @@ static void xprt_alloc_slot(struct rpc_task *task)
 		goto out_init_req;
 	switch (PTR_ERR(req)) {
 	case -ENOMEM:
-		rpc_delay(task, HZ >> 2);
 		dprintk("RPC:       dynamic allocation of request slot "
 				"failed! Retrying\n");
+		task->tk_status = -ENOMEM;
 		break;
 	case -EAGAIN:
 		rpc_sleep_on(&xprt->backlog, task, NULL);
 		dprintk("RPC:       waiting for request slot\n");
+	default:
+		task->tk_status = -EAGAIN;
 	}
-	task->tk_status = -EAGAIN;
 	return;
 out_init_req:
 	task->tk_status = 0;