nfsd4: centralize more calls to svc_xprt_received

Follow up on b48fa6b9 by moving all the
svc_xprt_received() calls for the main xprt to one place.  The clearing
of XPT_BUSY here is critical to the correctness of the server, so I'd
prefer it to be obvious where we do it.

The only substantive result is moving svc_xprt_received() after
svc_receive_deferred().  Other than a (likely insignificant) delay
waking up the next thread, that should be harmless.

Also reshuffle the exit code a little to skip a few other steps that we
don't care about the in the svc_delete_xprt() case.
Signed-off-by: J. Bruce Fields <bfields@redhat.com>

net/sunrpc/svc_xprt.c

@@ -716,7 +716,10 @@ int svc_recv(struct svc_rqst *rqstp, long timeout)
 	if (test_bit(XPT_CLOSE, &xprt->xpt_flags)) {
 		dprintk("svc_recv: found XPT_CLOSE\n");
 		svc_delete_xprt(xprt);
-	} else if (test_bit(XPT_LISTENER, &xprt->xpt_flags)) {
+		/* Leave XPT_BUSY set on the dead xprt: */
+		goto out;
+	}
+	if (test_bit(XPT_LISTENER, &xprt->xpt_flags)) {
 		struct svc_xprt *newxpt;
 		newxpt = xprt->xpt_ops->xpo_accept(xprt);
 		if (newxpt) {
@@ -741,28 +744,23 @@ int svc_recv(struct svc_rqst *rqstp, long timeout)
 			spin_unlock_bh(&serv->sv_lock);
 			svc_xprt_received(newxpt);
 		}
-		svc_xprt_received(xprt);
 	} else {
 		dprintk("svc: server %p, pool %u, transport %p, inuse=%d\n",
 			rqstp, pool->sp_id, xprt,
 			atomic_read(&xprt->xpt_ref.refcount));
 		rqstp->rq_deferred = svc_deferred_dequeue(xprt);
-		if (rqstp->rq_deferred) {
-			svc_xprt_received(xprt);
+		if (rqstp->rq_deferred)
 			len = svc_deferred_recv(rqstp);
-		} else {
+		else
 			len = xprt->xpt_ops->xpo_recvfrom(rqstp);
-			svc_xprt_received(xprt);
-		}
 		dprintk("svc: got len=%d\n", len);
 	}
+	svc_xprt_received(xprt);
 
 	/* No data, incomplete (TCP) read, or accept() */
-	if (len == 0 || len == -EAGAIN) {
-		rqstp->rq_res.len = 0;
-		svc_xprt_release(rqstp);
-		return -EAGAIN;
-	}
+	if (len == 0 || len == -EAGAIN)
+		goto out;
+
 	clear_bit(XPT_OLD, &xprt->xpt_flags);
 
 	rqstp->rq_secure = svc_port_is_privileged(svc_addr(rqstp));
@@ -771,6 +769,10 @@ int svc_recv(struct svc_rqst *rqstp, long timeout)
 	if (serv->sv_stats)
 		serv->sv_stats->netcnt++;
 	return len;
+out:
+	rqstp->rq_res.len = 0;
+	svc_xprt_release(rqstp);
+	return -EAGAIN;
 }
 EXPORT_SYMBOL_GPL(svc_recv);