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>

1 files changed, 97 insertions, 69 deletions

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);