tipc: simplify connection congestion handling

As a consequence of the recently introduced serialized access
to the socket in commit 8d94168a761819d10252bab1f8de6d7b202c3baa
("tipc: same receive code path for connection protocol and data
messages") we can make a number of simplifications in the
detection and handling of connection congestion situations.

- We don't need to keep two counters, one for sent messages and one
  for acked messages. There is no longer any risk for races between
  acknowledge messages arriving in BH and data message sending
  running in user context. So we merge this into one counter,
  'sent_unacked', which is incremented at sending and subtracted
  from at acknowledge reception.

- We don't need to set the 'congested' field in tipc_port to
  true before we sent the message, and clear it when sending
  is successful. (As a matter of fact, it was never necessary;
  the field was set in link_schedule_port() before any wakeup
  could arrive anyway.)

- We keep the conditions for link congestion and connection connection
  congestion separated. There would otherwise be a risk that an arriving
  acknowledge message may wake up a user sleeping because of link
  congestion.

- We can simplify reception of acknowledge messages.

We also make some cosmetic/structural changes:

- We rename the 'congested' field to the more correct 'link_cong´.

- We rename 'conn_unacked' to 'rcv_unacked'

- We move the above mentioned fields from struct tipc_port to
  struct tipc_sock.

Signed-off-by: Jon Maloy <jon.maloy@ericsson.com>
Reviewed-by: Erik Hugne <erik.hugne@ericsson.com>
Reviewed-by: Ying Xue <ying.xue@windriver.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 23 insertions, 25 deletions

diff --git a/net/tipc/socket.c b/net/tipc/socket.c
index 1762323..ede78b1 100644
--- a/net/tipc/socket.c
+++ b/net/tipc/socket.c
@@ -207,7 +207,7 @@ static int tipc_sk_create(struct net *net, struct socket *sock,
 	sk->sk_data_ready = tipc_data_ready;
 	sk->sk_write_space = tipc_write_space;
 	tsk->conn_timeout = CONN_TIMEOUT_DEFAULT;
-	tsk->port.sent = 0;
+	tsk->sent_unacked = 0;
 	atomic_set(&tsk->dupl_rcvcnt, 0);
 	tipc_port_unlock(port);
 
@@ -513,12 +513,12 @@ static unsigned int tipc_poll(struct file *file, struct socket *sock,
 
 	switch ((int)sock->state) {
 	case SS_UNCONNECTED:
-		if (!tsk->port.congested)
+		if (!tsk->link_cong)
 			mask |= POLLOUT;
 		break;
 	case SS_READY:
 	case SS_CONNECTED:
-		if (!tsk->port.congested)
+		if (!tsk->link_cong && !tipc_sk_conn_cong(tsk))
 			mask |= POLLOUT;
 		/* fall thru' */
 	case SS_CONNECTING:
@@ -546,7 +546,7 @@ int tipc_sk_proto_rcv(struct tipc_sock *tsk, u32 *dnode, struct sk_buff *buf)
 {
 	struct tipc_msg *msg = buf_msg(buf);
 	struct tipc_port *port = &tsk->port;
-	int wakeable;
+	int conn_cong;
 
 	/* Ignore if connection cannot be validated: */
 	if (!port->connected || !tipc_port_peer_msg(port, msg))
@@ -555,13 +555,10 @@ int tipc_sk_proto_rcv(struct tipc_sock *tsk, u32 *dnode, struct sk_buff *buf)
 	port->probing_state = TIPC_CONN_OK;
 
 	if (msg_type(msg) == CONN_ACK) {
-		wakeable = tipc_port_congested(port) && port->congested;
-		port->acked += msg_msgcnt(msg);
-		if (!tipc_port_congested(port)) {
-			port->congested = 0;
-			if (wakeable)
-				tipc_port_wakeup(port);
-		}
+		conn_cong = tipc_sk_conn_cong(tsk);
+		tsk->sent_unacked -= msg_msgcnt(msg);
+		if (conn_cong)
+			tipc_sock_wakeup(tsk);
 	} else if (msg_type(msg) == CONN_PROBE) {
 		if (!tipc_msg_reverse(buf, dnode, TIPC_OK))
 			return TIPC_OK;
@@ -626,7 +623,7 @@ static int tipc_wait_for_sndmsg(struct socket *sock, long *timeo_p)
 			return sock_intr_errno(*timeo_p);
 
 		prepare_to_wait(sk_sleep(sk), &wait, TASK_INTERRUPTIBLE);
-		done = sk_wait_event(sk, timeo_p, !tsk->port.congested);
+		done = sk_wait_event(sk, timeo_p, !tsk->link_cong);
 		finish_wait(sk_sleep(sk), &wait);
 	} while (!done);
 	return 0;
@@ -800,7 +797,6 @@ static int tipc_wait_for_sndpkt(struct socket *sock, long *timeo_p)
 {
 	struct sock *sk = sock->sk;
 	struct tipc_sock *tsk = tipc_sk(sk);
-	struct tipc_port *port = &tsk->port;
 	DEFINE_WAIT(wait);
 	int done;
 
@@ -819,7 +815,9 @@ static int tipc_wait_for_sndpkt(struct socket *sock, long *timeo_p)
 
 		prepare_to_wait(sk_sleep(sk), &wait, TASK_INTERRUPTIBLE);
 		done = sk_wait_event(sk, timeo_p,
-				     (!port->congested || !port->connected));
+				     (!tsk->link_cong &&
+				      !tipc_sk_conn_cong(tsk)) ||
+				     !tsk->port.connected);
 		finish_wait(sk_sleep(sk), &wait);
 	} while (!done);
 	return 0;
@@ -856,7 +854,7 @@ static int tipc_send_stream(struct kiocb *iocb, struct socket *sock,
 	if (unlikely(dest)) {
 		rc = tipc_sendmsg(iocb, sock, m, dsz);
 		if (dsz && (dsz == rc))
-			tsk->port.sent = 1;
+			tsk->sent_unacked = 1;
 		return rc;
 	}
 	if (dsz > (uint)INT_MAX)
@@ -875,7 +873,6 @@ static int tipc_send_stream(struct kiocb *iocb, struct socket *sock,
 
 	timeo = sock_sndtimeo(sk, m->msg_flags & MSG_DONTWAIT);
 	dnode = tipc_port_peernode(port);
-	port->congested = 1;
 
 next:
 	mtu = port->max_pkt;
@@ -884,11 +881,10 @@ next:
 	if (unlikely(rc < 0))
 		goto exit;
 	do {
-		port->congested = 1;
-		if (likely(!tipc_port_congested(port))) {
+		if (likely(!tipc_sk_conn_cong(tsk))) {
 			rc = tipc_link_xmit2(buf, dnode, ref);
 			if (likely(!rc)) {
-				port->sent++;
+				tsk->sent_unacked++;
 				sent += send;
 				if (sent == dsz)
 					break;
@@ -903,8 +899,6 @@ next:
 		}
 		rc = tipc_wait_for_sndpkt(sock, &timeo);
 	} while (!rc);
-
-	port->congested = 0;
 exit:
 	if (iocb)
 		release_sock(sk);
@@ -1169,8 +1163,10 @@ restart:
 	/* Consume received message (optional) */
 	if (likely(!(flags & MSG_PEEK))) {
 		if ((sock->state != SS_READY) &&
-		    (++port->conn_unacked >= TIPC_CONNACK_INTV))
-			tipc_acknowledge(port->ref, port->conn_unacked);
+		    (++tsk->rcv_unacked >= TIPC_CONNACK_INTV)) {
+			tipc_acknowledge(port->ref, tsk->rcv_unacked);
+			tsk->rcv_unacked = 0;
+		}
 		advance_rx_queue(sk);
 	}
 exit:
@@ -1278,8 +1274,10 @@ restart:
 
 	/* Consume received message (optional) */
 	if (likely(!(flags & MSG_PEEK))) {
-		if (unlikely(++port->conn_unacked >= TIPC_CONNACK_INTV))
-			tipc_acknowledge(port->ref, port->conn_unacked);
+		if (unlikely(++tsk->rcv_unacked >= TIPC_CONNACK_INTV)) {
+			tipc_acknowledge(port->ref, tsk->rcv_unacked);
+			tsk->rcv_unacked = 0;
+		}
 		advance_rx_queue(sk);
 	}