batman-adv: Convert batadv_orig_node_vlan to kref

batman-adv uses a self-written reference implementation which is just based
on atomic_t. This is less obvious when reading the code than kref and
therefore increases the change that the reference counting will be missed.
Signed-off-by: Sven Eckelmann <sven@narfation.org>
Signed-off-by: Marek Lindner <mareklindner@neomailbox.ch>
Signed-off-by: Antonio Quartulli <a@unstable.cc>

net/batman-adv/originator.c

@@ -82,7 +82,7 @@ batadv_orig_node_vlan_get(struct batadv_orig_node *orig_node,
 		if (tmp->vid != vid)
 			continue;
 
-		if (!atomic_inc_not_zero(&tmp->refcount))
+		if (!kref_get_unless_zero(&tmp->refcount))
 			continue;
 
 		vlan = tmp;
@@ -123,7 +123,8 @@ batadv_orig_node_vlan_new(struct batadv_orig_node *orig_node,
 	if (!vlan)
 		goto out;
 
-	atomic_set(&vlan->refcount, 2);
+	kref_init(&vlan->refcount);
+	kref_get(&vlan->refcount);
 	vlan->vid = vid;
 
 	hlist_add_head_rcu(&vlan->list, &orig_node->vlan_list);
@@ -135,14 +136,27 @@ batadv_orig_node_vlan_new(struct batadv_orig_node *orig_node,
 }
 
 /**
- * batadv_orig_node_vlan_free_ref - decrement the refcounter and possibly free
- *  the originator-vlan object
+ * batadv_orig_node_vlan_release - release originator-vlan object from lists
+ *  and queue for free after rcu grace period
+ * @ref: kref pointer of the originator-vlan object
+ */
+static void batadv_orig_node_vlan_release(struct kref *ref)
+{
+	struct batadv_orig_node_vlan *orig_vlan;
+
+	orig_vlan = container_of(ref, struct batadv_orig_node_vlan, refcount);
+
+	kfree_rcu(orig_vlan, rcu);
+}
+
+/**
+ * batadv_orig_node_vlan_free_ref - decrement the refcounter and possibly
+ *  release the originator-vlan object
  * @orig_vlan: the originator-vlan object to release
  */
 void batadv_orig_node_vlan_free_ref(struct batadv_orig_node_vlan *orig_vlan)
 {
-	if (atomic_dec_and_test(&orig_vlan->refcount))
-		kfree_rcu(orig_vlan, rcu);
+	kref_put(&orig_vlan->refcount, batadv_orig_node_vlan_release);
 }
 
 int batadv_originator_init(struct batadv_priv *bat_priv)

net/batman-adv/types.h

@@ -197,7 +197,7 @@ struct batadv_orig_node_vlan {
 	unsigned short vid;
 	struct batadv_vlan_tt tt;
 	struct hlist_node list;
-	atomic_t refcount;
+	struct kref refcount;
 	struct rcu_head rcu;
 };