tipc: make resetting of links non-atomic

In order to facilitate future improvements to the locking structure, we
want to make resetting and establishing of links non-atomic. I.e., the
functions tipc_node_link_up() and tipc_node_link_down() should be called
from outside the node lock context, and grab/release the node lock
themselves. This requires that we can freeze the link state from the
moment it is set to RESETTING or PEER_RESET in one lock context until
it is set to RESET or ESTABLISHING in a later context. The recently
introduced link FSM makes this possible, so we are now ready to introduce
the above change.

This commit implements this.

Tested-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>

3 files changed, 127 insertions, 70 deletions

diff --git a/net/tipc/link.c b/net/tipc/link.c
index 9840b03348e1..3a92924711a1 100644
--- a/net/tipc/link.c
+++ b/net/tipc/link.c
@@ -489,8 +489,8 @@ int tipc_link_timeout(struct tipc_link *l, struct sk_buff_head *xmitq)
 		xmit = true;
 		mtyp = ACTIVATE_MSG;
 		break;
-	case LINK_RESETTING:
 	case LINK_PEER_RESET:
+	case LINK_RESETTING:
 	case LINK_FAILINGOVER:
 		break;
 	default:
diff --git a/net/tipc/msg.h b/net/tipc/msg.h
index 115bb2aa6bed..53d98ef78650 100644
--- a/net/tipc/msg.h
+++ b/net/tipc/msg.h
@@ -916,4 +916,33 @@ static inline bool __tipc_skb_queue_sorted(struct sk_buff_head *list,
 	return false;
 }
 
+/* tipc_skb_queue_splice_tail - append an skb list to lock protected list
+ * @list: the new list to append. Not lock protected
+ * @head: target list. Lock protected.
+ */
+static inline void tipc_skb_queue_splice_tail(struct sk_buff_head *list,
+					      struct sk_buff_head *head)
+{
+	spin_lock_bh(&head->lock);
+	skb_queue_splice_tail(list, head);
+	spin_unlock_bh(&head->lock);
+}
+
+/* tipc_skb_queue_splice_tail_init - merge two lock protected skb lists
+ * @list: the new list to add. Lock protected. Will be reinitialized
+ * @head: target list. Lock protected.
+ */
+static inline void tipc_skb_queue_splice_tail_init(struct sk_buff_head *list,
+						   struct sk_buff_head *head)
+{
+	struct sk_buff_head tmp;
+
+	__skb_queue_head_init(&tmp);
+
+	spin_lock_bh(&list->lock);
+	skb_queue_splice_tail_init(list, &tmp);
+	spin_unlock_bh(&list->lock);
+	tipc_skb_queue_splice_tail(&tmp, head);
+}
+
 #endif
diff --git a/net/tipc/node.c b/net/tipc/node.c
index d03e88f2273b..cdca57be85bf 100644
--- a/net/tipc/node.c
+++ b/net/tipc/node.c
@@ -66,8 +66,12 @@ enum {
 	NODE_SYNCH_END_EVT      = 0xcee
 };
 
-static void tipc_node_link_down(struct tipc_node *n, int bearer_id);
-static void node_lost_contact(struct tipc_node *n_ptr);
+static void __tipc_node_link_down(struct tipc_node *n, int *bearer_id,
+				  struct sk_buff_head *xmitq,
+				  struct tipc_media_addr **maddr);
+static void tipc_node_link_down(struct tipc_node *n, int bearer_id,
+				bool delete);
+static void node_lost_contact(struct tipc_node *n, struct sk_buff_head *inputq);
 static void node_established_contact(struct tipc_node *n_ptr);
 static void tipc_node_delete(struct tipc_node *node);
 static void tipc_node_timeout(unsigned long data);
@@ -275,9 +279,8 @@ void tipc_node_remove_conn(struct net *net, u32 dnode, u32 port)
 static void tipc_node_timeout(unsigned long data)
 {
 	struct tipc_node *n = (struct tipc_node *)data;
+	struct tipc_link_entry *le;
 	struct sk_buff_head xmitq;
-	struct tipc_link *l;
-	struct tipc_media_addr *maddr;
 	int bearer_id;
 	int rc = 0;
 
@@ -285,17 +288,16 @@ static void tipc_node_timeout(unsigned long data)
 
 	for (bearer_id = 0; bearer_id < MAX_BEARERS; bearer_id++) {
 		tipc_node_lock(n);
-		l = n->links[bearer_id].link;
-		if (l) {
+		le = &n->links[bearer_id];
+		if (le->link) {
 			/* Link tolerance may change asynchronously: */
-			tipc_node_calculate_timer(n, l);
-			rc = tipc_link_timeout(l, &xmitq);
-			if (rc & TIPC_LINK_DOWN_EVT)
-				tipc_node_link_down(n, bearer_id);
+			tipc_node_calculate_timer(n, le->link);
+			rc = tipc_link_timeout(le->link, &xmitq);
 		}
 		tipc_node_unlock(n);
-		maddr = &n->links[bearer_id].maddr;
-		tipc_bearer_xmit(n->net, bearer_id, &xmitq, maddr);
+		tipc_bearer_xmit(n->net, bearer_id, &xmitq, &le->maddr);
+		if (rc & TIPC_LINK_DOWN_EVT)
+			tipc_node_link_down(n, bearer_id, false);
 	}
 	if (!mod_timer(&n->timer, jiffies + n->keepalive_intv))
 		tipc_node_get(n);
@@ -303,18 +305,21 @@ static void tipc_node_timeout(unsigned long data)
 }
 
 /**
- * tipc_node_link_up - handle addition of link
- *
+ * __tipc_node_link_up - handle addition of link
+ * Node lock must be held by caller
  * Link becomes active (alone or shared) or standby, depending on its priority.
  */
-static void tipc_node_link_up(struct tipc_node *n, int bearer_id,
-			      struct sk_buff_head *xmitq)
+static void __tipc_node_link_up(struct tipc_node *n, int bearer_id,
+				struct sk_buff_head *xmitq)
 {
 	int *slot0 = &n->active_links[0];
 	int *slot1 = &n->active_links[1];
 	struct tipc_link *ol = node_active_link(n, 0);
 	struct tipc_link *nl = n->links[bearer_id].link;
 
+	if (!nl || !tipc_link_is_up(nl))
+		return;
+
 	if (n->working_links > 1) {
 		pr_warn("Attempt to establish 3rd link to %x\n", n->addr);
 		return;
@@ -356,28 +361,40 @@ static void tipc_node_link_up(struct tipc_node *n, int bearer_id,
 }
 
 /**
- * tipc_node_link_down - handle loss of link
+ * tipc_node_link_up - handle addition of link
+ *
+ * Link becomes active (alone or shared) or standby, depending on its priority.
  */
-static void tipc_node_link_down(struct tipc_node *n, int bearer_id)
+static void tipc_node_link_up(struct tipc_node *n, int bearer_id,
+			      struct sk_buff_head *xmitq)
 {
+	tipc_node_lock(n);
+	__tipc_node_link_up(n, bearer_id, xmitq);
+	tipc_node_unlock(n);
+}
+
+/**
+ * __tipc_node_link_down - handle loss of link
+ */
+static void __tipc_node_link_down(struct tipc_node *n, int *bearer_id,
+				  struct sk_buff_head *xmitq,
+				  struct tipc_media_addr **maddr)
+{
+	struct tipc_link_entry *le = &n->links[*bearer_id];
 	int *slot0 = &n->active_links[0];
 	int *slot1 = &n->active_links[1];
-	struct tipc_media_addr *maddr = &n->links[bearer_id].maddr;
 	int i, highest = 0;
 	struct tipc_link *l, *_l, *tnl;
-	struct sk_buff_head xmitq;
 
-	l = n->links[bearer_id].link;
+	l = n->links[*bearer_id].link;
 	if (!l || tipc_link_is_reset(l))
 		return;
 
-	__skb_queue_head_init(&xmitq);
-
 	n->working_links--;
 	n->action_flags |= TIPC_NOTIFY_LINK_DOWN;
-	n->link_id = l->peer_bearer_id << 16 | bearer_id;
+	n->link_id = l->peer_bearer_id << 16 | *bearer_id;
 
-	tipc_bearer_remove_dest(n->net, l->bearer_id, n->addr);
+	tipc_bearer_remove_dest(n->net, *bearer_id, n->addr);
 
 	pr_debug("Lost link <%s> on network plane %c\n",
 		 l->name, l->net_plane);
@@ -404,18 +421,40 @@ static void tipc_node_link_down(struct tipc_node *n, int bearer_id)
 
 	if (!tipc_node_is_up(n)) {
 		tipc_link_reset(l);
-		node_lost_contact(n);
+		node_lost_contact(n, &le->inputq);
 		return;
 	}
 
 	/* There is still a working link => initiate failover */
 	tnl = node_active_link(n, 0);
-	tipc_node_fsm_evt(n, NODE_FAILOVER_BEGIN_EVT);
 	n->sync_point = tnl->rcv_nxt + (U16_MAX / 2 - 1);
-	tipc_link_tnl_prepare(l, tnl, FAILOVER_MSG, &xmitq);
+	tipc_link_tnl_prepare(l, tnl, FAILOVER_MSG, xmitq);
 	tipc_link_reset(l);
 	tipc_link_fsm_evt(l, LINK_FAILOVER_BEGIN_EVT);
-	tipc_bearer_xmit(n->net, tnl->bearer_id, &xmitq, maddr);
+	tipc_node_fsm_evt(n, NODE_FAILOVER_BEGIN_EVT);
+	*maddr = &n->links[tnl->bearer_id].maddr;
+	*bearer_id = tnl->bearer_id;
+}
+
+static void tipc_node_link_down(struct tipc_node *n, int bearer_id, bool delete)
+{
+	struct tipc_link_entry *le = &n->links[bearer_id];
+	struct tipc_media_addr *maddr;
+	struct sk_buff_head xmitq;
+
+	__skb_queue_head_init(&xmitq);
+
+	tipc_node_lock(n);
+	__tipc_node_link_down(n, &bearer_id, &xmitq, &maddr);
+	if (delete && le->link) {
+		kfree(le->link);
+		le->link = NULL;
+		n->link_cnt--;
+	}
+	tipc_node_unlock(n);
+
+	tipc_bearer_xmit(n->net, bearer_id, &xmitq, maddr);
+	tipc_sk_rcv(n->net, &le->inputq);
 }
 
 bool tipc_node_is_up(struct tipc_node *n)
@@ -437,7 +476,7 @@ void tipc_node_check_dest(struct net *net, u32 onode,
 	bool sign_match = false;
 	bool link_up = false;
 	bool accept_addr = false;
-
+	bool reset = true;
 	*dupl_addr = false;
 	*respond = false;
 
@@ -460,6 +499,7 @@ void tipc_node_check_dest(struct net *net, u32 onode,
 
 	if (sign_match && addr_match && link_up) {
 		/* All is fine. Do nothing. */
+		reset = false;
 	} else if (sign_match && addr_match && !link_up) {
 		/* Respond. The link will come up in due time */
 		*respond = true;
@@ -531,29 +571,21 @@ void tipc_node_check_dest(struct net *net, u32 onode,
 	}
 	memcpy(&l->media_addr, maddr, sizeof(*maddr));
 	memcpy(curr_maddr, maddr, sizeof(*maddr));
-	tipc_node_link_down(n, b->identity);
 exit:
 	tipc_node_unlock(n);
+	if (reset)
+		tipc_node_link_down(n, b->identity, false);
 	tipc_node_put(n);
 }
 
 void tipc_node_delete_links(struct net *net, int bearer_id)
 {
 	struct tipc_net *tn = net_generic(net, tipc_net_id);
-	struct tipc_link *l;
 	struct tipc_node *n;
 
 	rcu_read_lock();
 	list_for_each_entry_rcu(n, &tn->node_list, list) {
-		tipc_node_lock(n);
-		l = n->links[bearer_id].link;
-		if (l) {
-			tipc_node_link_down(n, bearer_id);
-			n->links[bearer_id].link = NULL;
-			n->link_cnt--;
-		}
-		tipc_node_unlock(n);
-		kfree(l);
+		tipc_node_link_down(n, bearer_id, true);
 	}
 	rcu_read_unlock();
 }
@@ -561,19 +593,14 @@ void tipc_node_delete_links(struct net *net, int bearer_id)
 static void tipc_node_reset_links(struct tipc_node *n)
 {
 	char addr_string[16];
-	u32 i;
-
-	tipc_node_lock(n);
+	int i;
 
 	pr_warn("Resetting all links to %s\n",
 		tipc_addr_string_fill(addr_string, n->addr));
 
 	for (i = 0; i < MAX_BEARERS; i++) {
-		if (!n->links[i].link)
-			continue;
-		tipc_node_link_down(n, i);
+		tipc_node_link_down(n, i, false);
 	}
-	tipc_node_unlock(n);
 }
 
 void tipc_node_attach_link(struct tipc_node *n_ptr, struct tipc_link *l_ptr)
@@ -798,10 +825,12 @@ static void node_established_contact(struct tipc_node *n_ptr)
 	tipc_bclink_add_node(n_ptr->net, n_ptr->addr);
 }
 
-static void node_lost_contact(struct tipc_node *n_ptr)
+static void node_lost_contact(struct tipc_node *n_ptr,
+			      struct sk_buff_head *inputq)
 {
 	char addr_string[16];
 	struct tipc_sock_conn *conn, *safe;
+	struct tipc_link *l;
 	struct list_head *conns = &n_ptr->conn_sks;
 	struct sk_buff *skb;
 	struct tipc_net *tn = net_generic(n_ptr->net, tipc_net_id);
@@ -827,14 +856,11 @@ static void node_lost_contact(struct tipc_node *n_ptr)
 
 	/* Abort any ongoing link failover */
 	for (i = 0; i < MAX_BEARERS; i++) {
-		struct tipc_link *l_ptr = n_ptr->links[i].link;
-		if (!l_ptr)
-			continue;
-		tipc_link_fsm_evt(l_ptr, LINK_FAILOVER_END_EVT);
-		kfree_skb(l_ptr->failover_reasm_skb);
-		l_ptr->failover_reasm_skb = NULL;
-		tipc_link_reset_fragments(l_ptr);
+		l = n_ptr->links[i].link;
+		if (l)
+			tipc_link_fsm_evt(l, LINK_FAILOVER_END_EVT);
 	}
+
 	/* Prevent re-contact with node until cleanup is done */
 	tipc_node_fsm_evt(n_ptr, SELF_LOST_CONTACT_EVT);
 
@@ -848,7 +874,7 @@ static void node_lost_contact(struct tipc_node *n_ptr)
 				      conn->peer_node, conn->port,
 				      conn->peer_port, TIPC_ERR_NO_NODE);
 		if (likely(skb)) {
-			skb_queue_tail(n_ptr->inputq, skb);
+			skb_queue_tail(inputq, skb);
 			n_ptr->action_flags |= TIPC_MSG_EVT;
 		}
 		list_del(&conn->list);
@@ -1025,9 +1051,9 @@ int tipc_node_xmit(struct net *net, struct sk_buff_head *list,
 		l = tipc_node_select_link(n, selector, &bearer_id, &maddr);
 		if (likely(l))
 			rc = tipc_link_xmit(l, list, &xmitq);
-		if (unlikely(rc == -ENOBUFS))
-			tipc_node_link_down(n, bearer_id);
 		tipc_node_unlock(n);
+		if (unlikely(rc == -ENOBUFS))
+			tipc_node_link_down(n, bearer_id, false);
 		tipc_node_put(n);
 	}
 	if (likely(!rc)) {
@@ -1081,8 +1107,8 @@ static bool tipc_node_check_state(struct tipc_node *n, struct sk_buff *skb,
 	u16 rcv_nxt, syncpt, dlv_nxt;
 	int state = n->state;
 	struct tipc_link *l, *pl = NULL;
-	struct sk_buff_head;
-	int i;
+	struct tipc_media_addr *maddr;
+	int i, pb_id;
 
 	l = n->links[bearer_id].link;
 	if (!l)
@@ -1123,9 +1149,11 @@ static bool tipc_node_check_state(struct tipc_node *n, struct sk_buff *skb,
 	/* Initiate or update failover mode if applicable */
 	if ((usr == TUNNEL_PROTOCOL) && (mtyp == FAILOVER_MSG)) {
 		syncpt = oseqno + exp_pkts - 1;
-		if (pl && tipc_link_is_up(pl))
-			tipc_node_link_down(n, pl->bearer_id);
-
+		if (pl && tipc_link_is_up(pl)) {
+			pb_id = pl->bearer_id;
+			__tipc_node_link_down(n, &pb_id, xmitq, &maddr);
+			tipc_skb_queue_splice_tail_init(pl->inputq, l->inputq);
+		}
 		/* If pkts arrive out of order, use lowest calculated syncpt */
 		if (less(syncpt, n->sync_point))
 			n->sync_point = syncpt;
@@ -1146,7 +1174,7 @@ static bool tipc_node_check_state(struct tipc_node *n, struct sk_buff *skb,
 		syncpt = iseqno + exp_pkts - 1;
 		if (!tipc_link_is_up(l)) {
 			tipc_link_fsm_evt(l, LINK_ESTABLISH_EVT);
-			tipc_node_link_up(n, bearer_id, xmitq);
+			__tipc_node_link_up(n, bearer_id, xmitq);
 		}
 		if (n->state == SELF_UP_PEER_UP) {
 			n->sync_point = syncpt;
@@ -1224,7 +1252,7 @@ void tipc_rcv(struct net *net, struct sk_buff *skb, struct tipc_bearer *b)
 	if (unlikely(msg_user(hdr) == LINK_PROTOCOL))
 		tipc_bclink_sync_state(n, hdr);
 
-	/* Release acked broadcast messages */
+	/* Release acked broadcast packets */
 	if (unlikely(n->bclink.acked != msg_bcast_ack(hdr)))
 		tipc_bclink_acknowledge(n, msg_bcast_ack(hdr));
 
@@ -1233,14 +1261,14 @@ void tipc_rcv(struct net *net, struct sk_buff *skb, struct tipc_bearer *b)
 		rc = tipc_link_rcv(le->link, skb, &xmitq);
 		skb = NULL;
 	}
+unlock:
+	tipc_node_unlock(n);
 
 	if (unlikely(rc & TIPC_LINK_UP_EVT))
 		tipc_node_link_up(n, bearer_id, &xmitq);
 
 	if (unlikely(rc & TIPC_LINK_DOWN_EVT))
-		tipc_node_link_down(n, bearer_id);
-unlock:
-	tipc_node_unlock(n);
+		tipc_node_link_down(n, bearer_id, false);
 
 	if (!skb_queue_empty(&le->inputq))
 		tipc_sk_rcv(net, &le->inputq);