batman-adv: add reference counting for type batadv_tt_orig_list_entry

The batadv_tt_orig_list_entry structure didn't have any refcounting mechanism so
far. This patch introduces it and makes the structure being usable in much more
complex context.

Signed-off-by: Antonio Quartulli <ordex@autistici.org>

diff --git a/net/batman-adv/translation-table.c b/net/batman-adv/translation-table.c
index 99dd8f75b3ff20f0d2a277e1f65ffc284b002f2e..eb8490e504e257f7f28fd56be88f3eabfb00fd68 100644 (file)
--- a/net/batman-adv/translation-table.c
+++ b/net/batman-adv/translation-table.c
@@ -152,6 +152,8 @@ static void batadv_tt_orig_list_entry_free_rcu(struct rcu_head *rcu)
 static void
 batadv_tt_orig_list_entry_free_ref(struct batadv_tt_orig_list_entry *orig_entry)
 {
+       if (!atomic_dec_and_test(&orig_entry->refcount))
+               return;
        /* to avoid race conditions, immediately decrease the tt counter */
        atomic_dec(&orig_entry->orig_node->tt_size);
        call_rcu(&orig_entry->rcu, batadv_tt_orig_list_entry_free_rcu);
@@ -625,50 +627,82 @@ static void batadv_tt_changes_list_free(struct batadv_priv *bat_priv)
        spin_unlock_bh(&bat_priv->tt_changes_list_lock);
 }
 
-/* find out if an orig_node is already in the list of a tt_global_entry.
- * returns 1 if found, 0 otherwise
+/* retrieves the orig_tt_list_entry belonging to orig_node from the
+ * batadv_tt_global_entry list
+ *
+ * returns it with an increased refcounter, NULL if not found
  */
-static bool
-batadv_tt_global_entry_has_orig(const struct batadv_tt_global_entry *entry,
-                               const struct batadv_orig_node *orig_node)
+static struct batadv_tt_orig_list_entry *
+batadv_tt_global_orig_entry_find(const struct batadv_tt_global_entry *entry,
+                                const struct batadv_orig_node *orig_node)
 {
-       struct batadv_tt_orig_list_entry *tmp_orig_entry;
+       struct batadv_tt_orig_list_entry *tmp_orig_entry, *orig_entry = NULL;
        const struct hlist_head *head;
        struct hlist_node *node;
-       bool found = false;
 
        rcu_read_lock();
        head = &entry->orig_list;
        hlist_for_each_entry_rcu(tmp_orig_entry, node, head, list) {
-               if (tmp_orig_entry->orig_node == orig_node) {
-                       found = true;
-                       break;
-               }
+               if (tmp_orig_entry->orig_node != orig_node)
+                       continue;
+               if (!atomic_inc_not_zero(&tmp_orig_entry->refcount))
+                       continue;
+
+               orig_entry = tmp_orig_entry;
+               break;
        }
        rcu_read_unlock();
+
+       return orig_entry;
+}
+
+/* find out if an orig_node is already in the list of a tt_global_entry.
+ * returns true if found, false otherwise
+ */
+static bool
+batadv_tt_global_entry_has_orig(const struct batadv_tt_global_entry *entry,
+                               const struct batadv_orig_node *orig_node)
+{
+       struct batadv_tt_orig_list_entry *orig_entry;
+       bool found = false;
+
+       orig_entry = batadv_tt_global_orig_entry_find(entry, orig_node);
+       if (orig_entry) {
+               found = true;
+               batadv_tt_orig_list_entry_free_ref(orig_entry);
+       }
+
        return found;
 }
 
 static void
-batadv_tt_global_add_orig_entry(struct batadv_tt_global_entry *tt_global_entry,
+batadv_tt_global_orig_entry_add(struct batadv_tt_global_entry *tt_global,
                                struct batadv_orig_node *orig_node, int ttvn)
 {
        struct batadv_tt_orig_list_entry *orig_entry;
 
+       orig_entry = batadv_tt_global_orig_entry_find(tt_global, orig_node);
+       if (orig_entry)
+               goto out;
+
        orig_entry = kzalloc(sizeof(*orig_entry), GFP_ATOMIC);
        if (!orig_entry)
-               return;
+               goto out;
 
        INIT_HLIST_NODE(&orig_entry->list);
        atomic_inc(&orig_node->refcount);
        atomic_inc(&orig_node->tt_size);
        orig_entry->orig_node = orig_node;
        orig_entry->ttvn = ttvn;
+       atomic_set(&orig_entry->refcount, 2);
 
-       spin_lock_bh(&tt_global_entry->list_lock);
+       spin_lock_bh(&tt_global->list_lock);
        hlist_add_head_rcu(&orig_entry->list,
-                          &tt_global_entry->orig_list);
-       spin_unlock_bh(&tt_global_entry->list_lock);
+                          &tt_global->orig_list);
+       spin_unlock_bh(&tt_global->list_lock);
+out:
+       if (orig_entry)
+               batadv_tt_orig_list_entry_free_ref(orig_entry);
 }
 
 /* caller must hold orig_node refcount */
@@ -709,9 +743,6 @@ int batadv_tt_global_add(struct batadv_priv *bat_priv,
                        batadv_tt_global_entry_free_ref(tt_global_entry);
                        goto out_remove;
                }
-
-               batadv_tt_global_add_orig_entry(tt_global_entry, orig_node,
-                                               ttvn);
        } else {
                /* there is already a global entry, use this one. */
 
@@ -728,11 +759,9 @@ int batadv_tt_global_add(struct batadv_priv *bat_priv,
                        tt_global_entry->roam_at = 0;
                }
 
-               if (!batadv_tt_global_entry_has_orig(tt_global_entry,
-                                                    orig_node))
-                       batadv_tt_global_add_orig_entry(tt_global_entry,
-                                                       orig_node, ttvn);
        }
+       /* add the new orig_entry (if needed) */
+       batadv_tt_global_orig_entry_add(tt_global_entry, orig_node, ttvn);
 
        batadv_dbg(BATADV_DBG_TT, bat_priv,
                   "Creating new global tt entry: %pM (via %pM)\n",

diff --git a/net/batman-adv/types.h b/net/batman-adv/types.h
index 7812b6edda1330de55587dea6134fc7d626bc054..664ef81485554fbc09bd22baa2cbca6983d04f30 100644 (file)
--- a/net/batman-adv/types.h
+++ b/net/batman-adv/types.h
@@ -282,6 +282,7 @@ struct batadv_tt_global_entry {
 struct batadv_tt_orig_list_entry {
        struct batadv_orig_node *orig_node;
        uint8_t ttvn;
+       atomic_t refcount;
        struct rcu_head rcu;
        struct hlist_node list;
 };