batman-adv: concentrate all curr_gw related rcu operations in select/deselect functions

Signed-off-by: Marek Lindner <lindner_marek@yahoo.de>
Signed-off-by: Sven Eckelmann <sven@narfation.org>

1 files changed, 98 insertions, 72 deletions

diff --git a/net/batman-adv/gateway_client.c b/net/batman-adv/gateway_client.c
index 42a8a7ba06e6..2acd7a666bda 100644
--- a/net/batman-adv/gateway_client.c
+++ b/net/batman-adv/gateway_client.c
@@ -43,61 +43,75 @@ static void gw_node_free_ref(struct gw_node *gw_node)
                 call_rcu(&gw_node->rcu, gw_node_free_rcu);
 }
 
-struct orig_node *gw_get_selected(struct bat_priv *bat_priv)
+static struct gw_node *gw_get_selected_gw_node(struct bat_priv *bat_priv)
 {
-        struct gw_node *curr_gateway_tmp;
-        struct orig_node *orig_node = NULL;
+        struct gw_node *gw_node;
 
         rcu_read_lock();
-        curr_gateway_tmp = rcu_dereference(bat_priv->curr_gw);
-        if (!curr_gateway_tmp)
-                goto out;
-
-        orig_node = curr_gateway_tmp->orig_node;
-        if (!orig_node)
+        gw_node = rcu_dereference(bat_priv->curr_gw);
+        if (!gw_node)
                 goto out;
 
-        if (!atomic_inc_not_zero(&orig_node->refcount))
-                orig_node = NULL;
+        if (!atomic_inc_not_zero(&gw_node->refcount))
+                gw_node = NULL;
 
 out:
         rcu_read_unlock();
-        return orig_node;
+        return gw_node;
 }
 
-void gw_deselect(struct bat_priv *bat_priv)
+struct orig_node *gw_get_selected_orig(struct bat_priv *bat_priv)
 {
         struct gw_node *gw_node;
+        struct orig_node *orig_node = NULL;
 
-        spin_lock_bh(&bat_priv->gw_list_lock);
-        gw_node = rcu_dereference(bat_priv->curr_gw);
-        rcu_assign_pointer(bat_priv->curr_gw, NULL);
-        spin_unlock_bh(&bat_priv->gw_list_lock);
+        gw_node = gw_get_selected_gw_node(bat_priv);
+        if (!gw_node)
+                goto out;
+
+        rcu_read_lock();
+        orig_node = gw_node->orig_node;
+        if (!orig_node)
+                goto unlock;
+
+        if (!atomic_inc_not_zero(&orig_node->refcount))
+                orig_node = NULL;
 
+unlock:
+        rcu_read_unlock();
+out:
         if (gw_node)
                 gw_node_free_ref(gw_node);
+        return orig_node;
 }
 
 static void gw_select(struct bat_priv *bat_priv, struct gw_node *new_gw_node)
 {
         struct gw_node *curr_gw_node;
 
+        spin_lock_bh(&bat_priv->gw_list_lock);
+
         if (new_gw_node && !atomic_inc_not_zero(&new_gw_node->refcount))
                 new_gw_node = NULL;
 
-        spin_lock_bh(&bat_priv->gw_list_lock);
-        curr_gw_node = rcu_dereference(bat_priv->curr_gw);
+        curr_gw_node = bat_priv->curr_gw;
         rcu_assign_pointer(bat_priv->curr_gw, new_gw_node);
-        spin_unlock_bh(&bat_priv->gw_list_lock);
 
         if (curr_gw_node)
                 gw_node_free_ref(curr_gw_node);
+
+        spin_unlock_bh(&bat_priv->gw_list_lock);
+}
+
+void gw_deselect(struct bat_priv *bat_priv)
+{
+        gw_select(bat_priv, NULL);
 }
 
 void gw_election(struct bat_priv *bat_priv)
 {
         struct hlist_node *node;
-        struct gw_node *gw_node, *curr_gw, *curr_gw_tmp = NULL;
+        struct gw_node *gw_node, *curr_gw = NULL, *curr_gw_tmp = NULL;
         struct neigh_node *router;
         uint8_t max_tq = 0;
         uint32_t max_gw_factor = 0, tmp_gw_factor = 0;
@@ -112,25 +126,17 @@ void gw_election(struct bat_priv *bat_priv)
         if (atomic_read(&bat_priv->gw_mode) != GW_MODE_CLIENT)
                 return;
 
-        rcu_read_lock();
-        curr_gw = rcu_dereference(bat_priv->curr_gw);
-        if (curr_gw) {
-                rcu_read_unlock();
-                return;
-        }
+        curr_gw = gw_get_selected_gw_node(bat_priv);
+        if (!curr_gw)
+                goto out;
 
+        rcu_read_lock();
         if (hlist_empty(&bat_priv->gw_list)) {
-
-                if (curr_gw) {
-                        rcu_read_unlock();
-                        bat_dbg(DBG_BATMAN, bat_priv,
-                                "Removing selected gateway - "
-                                "no gateway in range\n");
-                        gw_deselect(bat_priv);
-                } else
-                        rcu_read_unlock();
-
-                return;
+                bat_dbg(DBG_BATMAN, bat_priv,
+                        "Removing selected gateway - "
+                        "no gateway in range\n");
+                gw_deselect(bat_priv);
+                goto unlock;
         }
 
         hlist_for_each_entry_rcu(gw_node, node, &bat_priv->gw_list, list) {
@@ -182,7 +188,7 @@ void gw_election(struct bat_priv *bat_priv)
         if (curr_gw != curr_gw_tmp) {
                 router = orig_node_get_router(curr_gw_tmp->orig_node);
                 if (!router)
-                        goto out;
+                        goto unlock;
 
                 if ((curr_gw) && (!curr_gw_tmp))
                         bat_dbg(DBG_BATMAN, bat_priv,
@@ -207,8 +213,11 @@ void gw_election(struct bat_priv *bat_priv)
                 gw_select(bat_priv, curr_gw_tmp);
         }
 
-out:
+unlock:
         rcu_read_unlock();
+out:
+        if (curr_gw)
+                gw_node_free_ref(curr_gw);
 }
 
 void gw_check_election(struct bat_priv *bat_priv, struct orig_node *orig_node)
@@ -217,7 +226,7 @@ void gw_check_election(struct bat_priv *bat_priv, struct orig_node *orig_node)
         struct neigh_node *router_gw = NULL, *router_orig = NULL;
         uint8_t gw_tq_avg, orig_tq_avg;
 
-        curr_gw_orig = gw_get_selected(bat_priv);
+        curr_gw_orig = gw_get_selected_orig(bat_priv);
         if (!curr_gw_orig)
                 goto deselect;
 
@@ -299,7 +308,11 @@ void gw_node_update(struct bat_priv *bat_priv,
                     struct orig_node *orig_node, uint8_t new_gwflags)
 {
         struct hlist_node *node;
-        struct gw_node *gw_node;
+        struct gw_node *gw_node, *curr_gw;
+
+        curr_gw = gw_get_selected_gw_node(bat_priv);
+        if (!curr_gw)
+                goto out;
 
         rcu_read_lock();
         hlist_for_each_entry_rcu(gw_node, node, &bat_priv->gw_list, list) {
@@ -320,22 +333,26 @@ void gw_node_update(struct bat_priv *bat_priv,
                                 "Gateway %pM removed from gateway list\n",
                                 orig_node->orig);
 
-                        if (gw_node == rcu_dereference(bat_priv->curr_gw)) {
-                                rcu_read_unlock();
-                                gw_deselect(bat_priv);
-                                return;
-                        }
+                        if (gw_node == curr_gw)
+                                goto deselect;
                 }
 
-                rcu_read_unlock();
-                return;
+                goto unlock;
         }
-        rcu_read_unlock();
 
         if (new_gwflags == 0)
-                return;
+                goto unlock;
 
         gw_node_add(bat_priv, orig_node, new_gwflags);
+        goto unlock;
+
+deselect:
+        gw_deselect(bat_priv);
+unlock:
+        rcu_read_unlock();
+out:
+        if (curr_gw)
+                gw_node_free_ref(curr_gw);
 }
 
 void gw_node_delete(struct bat_priv *bat_priv, struct orig_node *orig_node)
@@ -345,9 +362,12 @@ void gw_node_delete(struct bat_priv *bat_priv, struct orig_node *orig_node)
 
 void gw_node_purge(struct bat_priv *bat_priv)
 {
-        struct gw_node *gw_node;
+        struct gw_node *gw_node, *curr_gw;
         struct hlist_node *node, *node_tmp;
         unsigned long timeout = 2 * PURGE_TIMEOUT * HZ;
+        char do_deselect = 0;
+
+        curr_gw = gw_get_selected_gw_node(bat_priv);
 
         spin_lock_bh(&bat_priv->gw_list_lock);
 
@@ -358,15 +378,21 @@ void gw_node_purge(struct bat_priv *bat_priv)
                     atomic_read(&bat_priv->mesh_state) == MESH_ACTIVE)
                         continue;
 
-                if (rcu_dereference(bat_priv->curr_gw) == gw_node)
-                        gw_deselect(bat_priv);
+                if (curr_gw == gw_node)
+                        do_deselect = 1;
 
                 hlist_del_rcu(&gw_node->list);
                 gw_node_free_ref(gw_node);
         }
 
-
         spin_unlock_bh(&bat_priv->gw_list_lock);
+
+        /* gw_deselect() needs to acquire the gw_list_lock */
+        if (do_deselect)
+                gw_deselect(bat_priv);
+
+        if (curr_gw)
+                gw_node_free_ref(curr_gw);
 }
 
 /**
@@ -385,22 +411,22 @@ static int _write_buffer_text(struct bat_priv *bat_priv,
         if (!router)
                 goto out;
 
-        rcu_read_lock();
-        curr_gw = rcu_dereference(bat_priv->curr_gw);
+        curr_gw = gw_get_selected_gw_node(bat_priv);
 
         ret = seq_printf(seq, "%s %pM (%3i) %pM [%10s]: %3i - %i%s/%i%s\n",
-                       (curr_gw == gw_node ? "=>" : "  "),
-                       gw_node->orig_node->orig,
-                       router->tq_avg, router->addr,
-                       router->if_incoming->net_dev->name,
-                       gw_node->orig_node->gw_flags,
-                       (down > 2048 ? down / 1024 : down),
-                       (down > 2048 ? "MBit" : "KBit"),
-                       (up > 2048 ? up / 1024 : up),
-                       (up > 2048 ? "MBit" : "KBit"));
+                         (curr_gw == gw_node ? "=>" : "  "),
+                         gw_node->orig_node->orig,
+                         router->tq_avg, router->addr,
+                         router->if_incoming->net_dev->name,
+                         gw_node->orig_node->gw_flags,
+                         (down > 2048 ? down / 1024 : down),
+                         (down > 2048 ? "MBit" : "KBit"),
+                         (up > 2048 ? up / 1024 : up),
+                         (up > 2048 ? "MBit" : "KBit"));
 
-        rcu_read_unlock();
         neigh_node_free_ref(router);
+        if (curr_gw)
+                gw_node_free_ref(curr_gw);
 out:
         return ret;
 }
@@ -459,6 +485,7 @@ int gw_is_target(struct bat_priv *bat_priv, struct sk_buff *skb)
         struct iphdr *iphdr;
         struct ipv6hdr *ipv6hdr;
         struct udphdr *udphdr;
+        struct gw_node *curr_gw;
         unsigned int header_len = 0;
 
         if (atomic_read(&bat_priv->gw_mode) == GW_MODE_OFF)
@@ -523,12 +550,11 @@ int gw_is_target(struct bat_priv *bat_priv, struct sk_buff *skb)
         if (atomic_read(&bat_priv->gw_mode) == GW_MODE_SERVER)
                 return -1;
 
-        rcu_read_lock();
-        if (!rcu_dereference(bat_priv->curr_gw)) {
-                rcu_read_unlock();
+        curr_gw = gw_get_selected_gw_node(bat_priv);
+        if (!curr_gw)
                 return 0;
-        }
-        rcu_read_unlock();
 
+        if (curr_gw)
+                gw_node_free_ref(curr_gw);
         return 1;
 }