tipc: use bearer index when looking up active links

struct tipc_node currently holds two arrays of link pointers; one,
indexed by bearer identity, which contains all links irrespective of
current state, and one two-slot array for the currently active link
or links. The latter array contains direct pointers into the elements
of the former. This has the effect that we cannot know the bearer id of
a link when accessing it via the "active_links[]" array without actually
dereferencing the pointer, something we want to avoid in some cases.

In this commit, we do instead store the bearer identity in the
"active_links" array, and use this as an index to find the right element
in the overall link entry array. This change should be seen as a
preparation for the later commits in this series.
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/node.c

@@ -142,6 +142,8 @@ struct tipc_node *tipc_node_create(struct net *net, u32 addr)
 	list_add_tail_rcu(&n_ptr->list, &temp_node->list);
 	n_ptr->action_flags = TIPC_WAIT_PEER_LINKS_DOWN;
 	n_ptr->signature = INVALID_NODE_SIG;
+	n_ptr->active_links[0] = INVALID_BEARER_ID;
+	n_ptr->active_links[1] = INVALID_BEARER_ID;
 	tipc_node_get(n_ptr);
 exit:
 	spin_unlock_bh(&tn->node_list_lock);
@@ -227,12 +229,13 @@ void tipc_node_remove_conn(struct net *net, u32 dnode, u32 port)
  */
 void tipc_node_link_up(struct tipc_node *n, int bearer_id)
 {
-	struct tipc_link_entry **actv = &n->active_links[0];
-	struct tipc_link_entry *le = &n->links[bearer_id];
-	struct tipc_link *l = le->link;
+	int *slot0 = &n->active_links[0];
+	int *slot1 = &n->active_links[1];
+	struct tipc_link_entry *links = n->links;
+	struct tipc_link *l = n->links[bearer_id].link;
 
 	/* Leave room for tunnel header when returning 'mtu' to users: */
-	n->links[bearer_id].mtu = l->mtu - INT_H_SIZE;
+	links[bearer_id].mtu = l->mtu - INT_H_SIZE;
 
 	n->working_links++;
 	n->action_flags |= TIPC_NOTIFY_LINK_UP;
@@ -242,55 +245,30 @@ void tipc_node_link_up(struct tipc_node *n, int bearer_id)
 		 l->name, l->net_plane);
 
 	/* No active links ? => take both active slots */
-	if (!actv[0]) {
-		actv[0] = le;
-		actv[1] = le;
+	if (*slot0 < 0) {
+		*slot0 = bearer_id;
+		*slot1 = bearer_id;
 		node_established_contact(n);
 		return;
 	}
-	if (l->priority < actv[0]->link->priority) {
+
+	/* Lower prio than current active ? => no slot */
+	if (l->priority < links[*slot0].link->priority) {
 		pr_debug("New link <%s> becomes standby\n", l->name);
 		return;
 	}
-	tipc_link_dup_queue_xmit(actv[0]->link, l);
+	tipc_link_dup_queue_xmit(links[*slot0].link, l);
 
-	/* Take one active slot if applicable */
-	if (l->priority == actv[0]->link->priority) {
-		actv[0] = le;
+	/* Same prio as current active ? => take one slot */
+	if (l->priority == links[*slot0].link->priority) {
+		*slot0 = bearer_id;
 		return;
 	}
-	/* Higher prio than current active? => take both active slots */
-	pr_debug("Old l <%s> becomes standby\n", actv[0]->link->name);
-	if (actv[1] != actv[0])
-		pr_debug("Old link <%s> now standby\n", actv[1]->link->name);
-	actv[0] = le;
-	actv[1] = le;
-}
-
-/**
- * node_select_active_links - select which working links should be active
- */
-static void node_select_active_links(struct tipc_node *n)
-{
-	struct tipc_link_entry **actv = &n->active_links[0];
-	struct tipc_link *l;
-	u32 b, highest = 0;
 
-	actv[0] = NULL;
-	actv[1] = NULL;
-
-	for (b = 0; b < MAX_BEARERS; b++) {
-		l = n->links[b].link;
-		if (!l || !tipc_link_is_up(l) || (l->priority < highest))
-			continue;
-		if (l->priority > highest) {
-			highest = l->priority;
-			actv[0] = &n->links[b];
-			actv[1] = &n->links[b];
-			continue;
-		}
-		actv[1] = &n->links[b];
-	}
+	/* Higher prio than current active => take both active slots */
+	pr_debug("Old link <%s> now standby\n", links[*slot0].link->name);
+	*slot0 = bearer_id;
+	*slot1 = bearer_id;
 }
 
 /**
@@ -298,32 +276,36 @@ static void node_select_active_links(struct tipc_node *n)
  */
 void tipc_node_link_down(struct tipc_node *n, int bearer_id)
 {
-	struct tipc_link_entry **actv = &n->active_links[0];
-	struct tipc_link_entry *le = &n->links[bearer_id];
-	struct tipc_link *l = le->link;
+	int *slot0 = &n->active_links[0];
+	int *slot1 = &n->active_links[1];
+	int i, highest = 0;
+	struct tipc_link *l, *_l;
 
+	l = n->links[bearer_id].link;
 	n->working_links--;
 	n->action_flags |= TIPC_NOTIFY_LINK_DOWN;
 	n->link_id = l->peer_bearer_id << 16 | l->bearer_id;
 
-	if (!tipc_link_is_active(l)) {
-		pr_debug("Lost standby link <%s> on network plane %c\n",
-			 l->name, l->net_plane);
-		return;
-	}
 	pr_debug("Lost link <%s> on network plane %c\n",
 		 l->name, l->net_plane);
 
-	/* Resdistribute active slots if applicable */
-	if (actv[0] == le)
-		actv[0] = actv[1];
-	if (actv[1] == le)
-		actv[1] = actv[0];
-
-	/* Last link of this priority? => select other ones if available */
-	if (actv[0] == le)
-		node_select_active_links(n);
-
+	/* Select new active link if any available */
+	*slot0 = INVALID_BEARER_ID;
+	*slot1 = INVALID_BEARER_ID;
+	for (i = 0; i < MAX_BEARERS; i++) {
+		_l = n->links[i].link;
+		if (!_l || !tipc_link_is_up(_l))
+			continue;
+		if (_l->priority < highest)
+			continue;
+		if (_l->priority > highest) {
+			highest = _l->priority;
+			*slot0 = i;
+			*slot1 = i;
+			continue;
+		}
+		*slot1 = i;
+	}
 	if (tipc_node_is_up(n))
 		tipc_link_failover_send_queue(l);
 	else
@@ -332,7 +314,7 @@ void tipc_node_link_down(struct tipc_node *n, int bearer_id)
 
 bool tipc_node_is_up(struct tipc_node *n)
 {
-	return n->active_links[0];
+	return n->active_links[0] != INVALID_BEARER_ID;
 }
 
 void tipc_node_check_dest(struct tipc_node *n, struct tipc_bearer *b,

net/tipc/node.h

@@ -45,6 +45,8 @@
 /* Out-of-range value for node signature */
 #define INVALID_NODE_SIG	0x10000
 
+#define INVALID_BEARER_ID -1
+
 /* Flags used to take different actions according to flag type
  * TIPC_WAIT_PEER_LINKS_DOWN: wait to see that peer's links are down
  * TIPC_WAIT_OWN_LINKS_DOWN: wait until peer node is declared down
@@ -105,7 +107,7 @@ struct tipc_link_entry {
  * @hash: links to adjacent nodes in unsorted hash chain
  * @inputq: pointer to input queue containing messages for msg event
  * @namedq: pointer to name table input queue with name table messages
- * @active_links: pointer into links[] array, identifying which links are active
+ * @active_links: bearer ids of active links, used as index into links[] array
  * @links: array containing references to all links to node
  * @action_flags: bit mask of different types of node actions
  * @bclink: broadcast-related info
@@ -126,7 +128,7 @@ struct tipc_node {
 	struct hlist_node hash;
 	struct sk_buff_head *inputq;
 	struct sk_buff_head *namedq;
-	struct tipc_link_entry *active_links[2];
+	int active_links[2];
 	struct tipc_link_entry links[MAX_BEARERS];
 	int action_flags;
 	struct tipc_node_bclink bclink;
@@ -176,25 +178,27 @@ static inline bool tipc_node_blocked(struct tipc_node *node)
 
 static inline struct tipc_link *node_active_link(struct tipc_node *n, int sel)
 {
-	struct tipc_link_entry *le = n->active_links[sel & 1];
+	int bearer_id = n->active_links[sel & 1];
 
-	if (likely(le))
-		return le->link;
+	if (unlikely(bearer_id == INVALID_BEARER_ID))
 		return NULL;
+
+	return n->links[bearer_id].link;
 }
 
-static inline uint tipc_node_get_mtu(struct net *net, u32 addr, u32 selector)
+static inline unsigned int tipc_node_get_mtu(struct net *net, u32 addr, u32 sel)
 {
 	struct tipc_node *n;
-	struct tipc_link_entry *le;
+	int bearer_id;
 	unsigned int mtu = MAX_MSG_SIZE;
 
 	n = tipc_node_find(net, addr);
 	if (unlikely(!n))
 		return mtu;
-	le = n->active_links[selector & 1];
-	if (likely(le))
-		mtu = le->mtu;
+
+	bearer_id = n->active_links[sel & 1];
+	if (likely(bearer_id != INVALID_BEARER_ID))
+		mtu = n->links[bearer_id].mtu;
 	tipc_node_put(n);
 	return mtu;
 }