SUNRPC: Small optimisation of client receive

Do not queue the client receive work if we're still processing.

Signed-off-by: Trond Myklebust <[e-mail]>

include/linux/sunrpc/xprtsock.h

···
 #define TCP_RPC_REPLY		(1UL << 6)
 
 #define XPRT_SOCK_CONNECTING	1U
+#define XPRT_SOCK_DATA_READY	(2)
 
 #endif /* __KERNEL__ */
 

net/sunrpc/xprtsock.c

···
 	sk->sk_error_report = transport->old_error_report;
 }
 
+static void xs_sock_reset_state_flags(struct rpc_xprt *xprt)
+{
+	struct sock_xprt *transport = container_of(xprt, struct sock_xprt, xprt);
+
+	clear_bit(XPRT_SOCK_DATA_READY, &transport->sock_state);
+}
+
 static void xs_sock_reset_connection_flags(struct rpc_xprt *xprt)
 {
 	smp_mb__before_atomic();
 	clear_bit(XPRT_CLOSE_WAIT, &xprt->state);
 	clear_bit(XPRT_CLOSING, &xprt->state);
+	xs_sock_reset_state_flags(xprt);
 	smp_mb__after_atomic();
 }
 
···
 		goto out;
 	for (;;) {
 		skb = skb_recv_datagram(sk, 0, 1, &err);
-		if (skb == NULL)
+		if (skb != NULL) {
+			xs_local_data_read_skb(&transport->xprt, sk, skb);
+			skb_free_datagram(sk, skb);
+			continue;
+		}
+		if (!test_and_clear_bit(XPRT_SOCK_DATA_READY, &transport->sock_state))
 			break;
-		xs_local_data_read_skb(&transport->xprt, sk, skb);
-		skb_free_datagram(sk, skb);
 	}
 out:
 	mutex_unlock(&transport->recv_mutex);
···
 		goto out;
 	for (;;) {
 		skb = skb_recv_datagram(sk, 0, 1, &err);
-		if (skb == NULL)
+		if (skb != NULL) {
+			xs_udp_data_read_skb(&transport->xprt, sk, skb);
+			skb_free_datagram(sk, skb);
+			continue;
+		}
+		if (!test_and_clear_bit(XPRT_SOCK_DATA_READY, &transport->sock_state))
 			break;
-		xs_udp_data_read_skb(&transport->xprt, sk, skb);
-		skb_free_datagram(sk, skb);
 	}
 out:
 	mutex_unlock(&transport->recv_mutex);
···
 	if (xprt != NULL) {
 		struct sock_xprt *transport = container_of(xprt,
 				struct sock_xprt, xprt);
-		queue_work(rpciod_workqueue, &transport->recv_worker);
+		if (!test_and_set_bit(XPRT_SOCK_DATA_READY, &transport->sock_state))
+			queue_work(rpciod_workqueue, &transport->recv_worker);
 	}
 	read_unlock_bh(&sk->sk_callback_lock);
 }
···
 	for (;;) {
 		lock_sock(sk);
 		read = tcp_read_sock(sk, &rd_desc, xs_tcp_data_recv);
-		release_sock(sk);
-		if (read <= 0)
-			break;
-		total += read;
+		if (read <= 0) {
+			clear_bit(XPRT_SOCK_DATA_READY, &transport->sock_state);
+			release_sock(sk);
+			if (!test_bit(XPRT_SOCK_DATA_READY, &transport->sock_state))
+				break;
+		} else {
+			release_sock(sk);
+			total += read;
+		}
 		rd_desc.count = 65536;
 	}
 out:
···
 	if (!(xprt = xprt_from_sock(sk)))
 		goto out;
 	transport = container_of(xprt, struct sock_xprt, xprt);
+	if (test_and_set_bit(XPRT_SOCK_DATA_READY, &transport->sock_state))
+		goto out;
 
 	/* Any data means we had a useful conversation, so
 	 * the we don't need to delay the next reconnect