tipc: reduce locking scope during packet reception

We convert packet/message reception according to the same principle
we have been using for message sending and timeout handling:

We move the function tipc_rcv() to node.c, hence handling the initial
packet reception at the link aggregation level. The function grabs
the node lock, selects the receiving link, and accesses it via a new
call tipc_link_rcv(). This function appends buffers to the input
queue for delivery upwards, but it may also append outgoing packets
to the xmit queue, just as we do during regular message sending. The
latter will happen when buffers are forwarded from the link backlog,
or when retransmission is requested.

Upon return of this function, and after having released the node lock,
tipc_rcv() delivers/tranmsits the contents of those queues, but it may
also perform actions such as link activation or reset, as indicated by
the return flags from the link.

This reduces the number of cpu cycles spent inside the node spinlock,
and reduces contention on that lock.

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

net/tipc/bcast.c

@@ -316,6 +316,29 @@ void tipc_bclink_update_link_state(struct tipc_node *n_ptr,
 	}
 }
 
+void tipc_bclink_sync_state(struct tipc_node *n, struct tipc_msg *hdr)
+{
+	u16 last = msg_last_bcast(hdr);
+	int mtyp = msg_type(hdr);
+
+	if (unlikely(msg_user(hdr) != LINK_PROTOCOL))
+		return;
+	if (mtyp == STATE_MSG) {
+		tipc_bclink_update_link_state(n, last);
+		return;
+	}
+	/* Compatibility: older nodes don't know BCAST_PROTOCOL synchronization,
+	 * and transfer synch info in LINK_PROTOCOL messages.
+	 */
+	if (tipc_node_is_up(n))
+		return;
+	if ((mtyp != RESET_MSG) && (mtyp != ACTIVATE_MSG))
+		return;
+	n->bclink.last_sent = last;
+	n->bclink.last_in = last;
+	n->bclink.oos_state = 0;
+}
+
 /**
  * bclink_peek_nack - monitor retransmission requests sent by other nodes
  *

net/tipc/bcast.h

@@ -133,5 +133,6 @@ void tipc_bclink_wakeup_users(struct net *net);
 int tipc_nl_add_bc_link(struct net *net, struct tipc_nl_msg *msg);
 int tipc_nl_bc_link_set(struct net *net, struct nlattr *attrs[]);
 void tipc_bclink_input(struct net *net);
+void tipc_bclink_sync_state(struct tipc_node *n, struct tipc_msg *msg);
 
 #endif

net/tipc/core.h

@@ -129,6 +129,11 @@ static inline int less(u16 left, u16 right)
 	return less_eq(left, right) && (mod(right) != mod(left));
 }
 
+static inline int in_range(u16 val, u16 min, u16 max)
+{
+	return !less(val, min) && !more(val, max);
+}
+
 #ifdef CONFIG_SYSCTL
 int tipc_register_sysctl(void);
 void tipc_unregister_sysctl(void);