SUNRPC: fix NFS client over TCP hangs due to packet loss (Bug 16494)

When reusing a TCP connection, ensure that it's aborted if a previous
shutdown attempt has been made on that connection so that the RPC over
TCP recovery mechanism succeeds.
Signed-off-by: Andy Chittenden <andyc.bluearc@gmail.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

net/sunrpc/xprtsock.c

@@ -1305,10 +1305,11 @@ static void xs_tcp_state_change(struct sock *sk)
 	if (!(xprt = xprt_from_sock(sk)))
 		goto out;
 	dprintk("RPC:       xs_tcp_state_change client %p...\n", xprt);
-	dprintk("RPC:       state %x conn %d dead %d zapped %d\n",
+	dprintk("RPC:       state %x conn %d dead %d zapped %d sk_shutdown %d\n",
 			sk->sk_state, xprt_connected(xprt),
 			sock_flag(sk, SOCK_DEAD),
-			sock_flag(sk, SOCK_ZAPPED));
+			sock_flag(sk, SOCK_ZAPPED),
+			sk->sk_shutdown);
 
 	switch (sk->sk_state) {
 	case TCP_ESTABLISHED:
@@ -1779,10 +1780,25 @@ static void xs_tcp_reuse_connection(struct rpc_xprt *xprt, struct sock_xprt *tra
 {
 	unsigned int state = transport->inet->sk_state;
 
-	if (state == TCP_CLOSE && transport->sock->state == SS_UNCONNECTED)
-		return;
-	if ((1 << state) & (TCPF_ESTABLISHED|TCPF_SYN_SENT))
-		return;
+	if (state == TCP_CLOSE && transport->sock->state == SS_UNCONNECTED) {
+		/* we don't need to abort the connection if the socket
+		 * hasn't undergone a shutdown
+		 */
+		if (transport->inet->sk_shutdown == 0)
+			return;
+		dprintk("RPC:       %s: TCP_CLOSEd and sk_shutdown set to %d\n",
+				__func__, transport->inet->sk_shutdown);
+	}
+	if ((1 << state) & (TCPF_ESTABLISHED|TCPF_SYN_SENT)) {
+		/* we don't need to abort the connection if the socket
+		 * hasn't undergone a shutdown
+		 */
+		if (transport->inet->sk_shutdown == 0)
+			return;
+		dprintk("RPC:       %s: ESTABLISHED/SYN_SENT "
+				"sk_shutdown set to %d\n",
+				__func__, transport->inet->sk_shutdown);
+	}
 	xs_abort_connection(xprt, transport);
 }