tipc: introduce per-link spinlock

As a preparation to allow parallel links to work more independently
from each other we introduce a per-link spinlock, to be stored in the
struct nodes's link entry area. Since the node lock still is a regular
spinlock there is no increase in parallellism at this stage.

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/link.c

@@ -1995,6 +1995,7 @@ int tipc_nl_link_reset_stats(struct sk_buff *skb, struct genl_info *info)
 	struct tipc_node *node;
 	struct nlattr *attrs[TIPC_NLA_LINK_MAX + 1];
 	struct net *net = sock_net(skb->sk);
+	struct tipc_link_entry *le;
 
 	if (!info->attrs[TIPC_NLA_LINK])
 		return -EINVAL;
@@ -2020,17 +2021,17 @@ int tipc_nl_link_reset_stats(struct sk_buff *skb, struct genl_info *info)
 	node = tipc_link_find_owner(net, link_name, &bearer_id);
 	if (!node)
 		return -EINVAL;
-
+	le = &node->links[bearer_id];
 	tipc_node_lock(node);
-
-	link = node->links[bearer_id].link;
+	spin_lock_bh(&le->lock);
+	link = le->link;
 	if (!link) {
 		tipc_node_unlock(node);
 		return -EINVAL;
 	}
 
 	link_reset_statistics(link);
-
+	spin_unlock_bh(&le->lock);
 	tipc_node_unlock(node);
 
 	return 0;

net/tipc/node.c

@@ -339,11 +339,13 @@ static void tipc_node_timeout(unsigned long data)
 	for (bearer_id = 0; bearer_id < MAX_BEARERS; bearer_id++) {
 		tipc_node_lock(n);
 		le = &n->links[bearer_id];
+		spin_lock_bh(&le->lock);
 		if (le->link) {
 			/* Link tolerance may change asynchronously: */
 			tipc_node_calculate_timer(n, le->link);
 			rc = tipc_link_timeout(le->link, &xmitq);
 		}
+		spin_unlock_bh(&le->lock);
 		tipc_node_unlock(n);
 		tipc_bearer_xmit(n->net, bearer_id, &xmitq, &le->maddr);
 		if (rc & TIPC_LINK_DOWN_EVT)
@@ -654,6 +656,7 @@ void tipc_node_check_dest(struct net *net, u32 onode,
 		if (n->state == NODE_FAILINGOVER)
 			tipc_link_fsm_evt(l, LINK_FAILOVER_BEGIN_EVT);
 		le->link = l;
+		spin_lock_init(&le->lock);
 		n->link_cnt++;
 		tipc_node_calculate_timer(n, l);
 		if (n->link_cnt == 1)
@@ -1033,20 +1036,6 @@ msg_full:
 	return -EMSGSIZE;
 }
 
-static struct tipc_link *tipc_node_select_link(struct tipc_node *n, int sel,
-					       int *bearer_id,
-					       struct tipc_media_addr **maddr)
-{
-	int id = n->active_links[sel & 1];
-
-	if (unlikely(id < 0))
-		return NULL;
-
-	*bearer_id = id;
-	*maddr = &n->links[id].maddr;
-	return n->links[id].link;
-}
-
 /**
  * tipc_node_xmit() is the general link level function for message sending
  * @net: the applicable net namespace
@@ -1059,26 +1048,32 @@ static struct tipc_link *tipc_node_select_link(struct tipc_node *n, int sel,
 int tipc_node_xmit(struct net *net, struct sk_buff_head *list,
 		   u32 dnode, int selector)
 {
-	struct tipc_link *l = NULL;
+	struct tipc_link_entry *le;
 	struct tipc_node *n;
 	struct sk_buff_head xmitq;
-	struct tipc_media_addr *maddr;
-	int bearer_id;
+	struct tipc_media_addr *maddr = NULL;
+	int bearer_id = -1;
 	int rc = -EHOSTUNREACH;
 
 	__skb_queue_head_init(&xmitq);
 	n = tipc_node_find(net, dnode);
 	if (likely(n)) {
 		tipc_node_lock(n);
-		l = tipc_node_select_link(n, selector, &bearer_id, &maddr);
-		if (likely(l))
-			rc = tipc_link_xmit(l, list, &xmitq);
+		bearer_id = n->active_links[selector & 1];
+		if (bearer_id >= 0) {
+			le = &n->links[bearer_id];
+			maddr = &le->maddr;
+			spin_lock_bh(&le->lock);
+			if (likely(le->link))
+				rc = tipc_link_xmit(le->link, list, &xmitq);
+			spin_unlock_bh(&le->lock);
+		}
 		tipc_node_unlock(n);
 		if (unlikely(rc == -ENOBUFS))
 			tipc_node_link_down(n, bearer_id, false);
 		tipc_node_put(n);
 	}
-	if (likely(!rc)) {
+	if (likely(!skb_queue_empty(&xmitq))) {
 		tipc_bearer_xmit(net, bearer_id, &xmitq, maddr);
 		return 0;
 	}
@@ -1374,7 +1369,9 @@ void tipc_rcv(struct net *net, struct sk_buff *skb, struct tipc_bearer *b)
 
 	/* Check and if necessary update node state */
 	if (likely(tipc_node_check_state(n, skb, bearer_id, &xmitq))) {
+		spin_lock_bh(&le->lock);
 		rc = tipc_link_rcv(le->link, skb, &xmitq);
+		spin_unlock_bh(&le->lock);
 		skb = NULL;
 	}
 unlock:

net/tipc/node.h

@@ -69,6 +69,7 @@ enum {
 
 struct tipc_link_entry {
 	struct tipc_link *link;
+	spinlock_t lock;   /* per-link */
 	u32 mtu;
 	struct sk_buff_head inputq;
 	struct tipc_media_addr maddr;
@@ -86,7 +87,7 @@ struct tipc_bclink_entry {
  * struct tipc_node - TIPC node structure
  * @addr: network address of node
  * @ref: reference counter to node object
- * @lock: spinlock governing access to structure
+ * @lock: rwlock governing access to structure
  * @net: the applicable net namespace
  * @hash: links to adjacent nodes in unsorted hash chain
  * @inputq: pointer to input queue containing messages for msg event