batman-adv: Convert batadv_softif_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/soft-interface.c

@@ -30,6 +30,7 @@
 #include <linux/if_vlan.h>
 #include <linux/jiffies.h>
 #include <linux/kernel.h>
+#include <linux/kref.h>
 #include <linux/list.h>
 #include <linux/lockdep.h>
 #include <linux/netdevice.h>
@@ -478,22 +479,34 @@ void batadv_interface_rx(struct net_device *soft_iface,
 }
 
 /**
- * batadv_softif_vlan_free_ref - decrease the vlan object refcounter and
- *  possibly free it
- * @vlan: the vlan object to release
+ * batadv_softif_vlan_release - release vlan from lists and queue for free after
+ *  rcu grace period
+ * @ref: kref pointer of the vlan object
  */
-void batadv_softif_vlan_free_ref(struct batadv_softif_vlan *vlan)
+static void batadv_softif_vlan_release(struct kref *ref)
 {
-	if (!vlan)
-		return;
+	struct batadv_softif_vlan *vlan;
+
+	vlan = container_of(ref, struct batadv_softif_vlan, refcount);
 
-	if (atomic_dec_and_test(&vlan->refcount)) {
 	spin_lock_bh(&vlan->bat_priv->softif_vlan_list_lock);
 	hlist_del_rcu(&vlan->list);
 	spin_unlock_bh(&vlan->bat_priv->softif_vlan_list_lock);
 
 	kfree_rcu(vlan, rcu);
-	}
+}
+
+/**
+ * batadv_softif_vlan_free_ref - decrease the vlan object refcounter and
+ *  possibly release it
+ * @vlan: the vlan object to release
+ */
+void batadv_softif_vlan_free_ref(struct batadv_softif_vlan *vlan)
+{
+	if (!vlan)
+		return;
+
+	kref_put(&vlan->refcount, batadv_softif_vlan_release);
 }
 
 /**
@@ -514,7 +527,7 @@ struct batadv_softif_vlan *batadv_softif_vlan_get(struct batadv_priv *bat_priv,
 		if (vlan_tmp->vid != vid)
 			continue;
 
-		if (!atomic_inc_not_zero(&vlan_tmp->refcount))
+		if (!kref_get_unless_zero(&vlan_tmp->refcount))
 			continue;
 
 		vlan = vlan_tmp;
@@ -549,7 +562,7 @@ int batadv_softif_create_vlan(struct batadv_priv *bat_priv, unsigned short vid)
 
 	vlan->bat_priv = bat_priv;
 	vlan->vid = vid;
-	atomic_set(&vlan->refcount, 1);
+	kref_init(&vlan->refcount);
 
 	atomic_set(&vlan->ap_isolation, 0);
 

net/batman-adv/sysfs.c

@@ -25,6 +25,7 @@
 #include <linux/fs.h>
 #include <linux/if.h>
 #include <linux/if_vlan.h>
+#include <linux/kref.h>
 #include <linux/kernel.h>
 #include <linux/netdevice.h>
 #include <linux/printk.h>
@@ -97,7 +98,7 @@ batadv_kobj_to_vlan(struct batadv_priv *bat_priv, struct kobject *obj)
 		if (vlan_tmp->kobj != obj)
 			continue;
 
-		if (!atomic_inc_not_zero(&vlan_tmp->refcount))
+		if (!kref_get_unless_zero(&vlan_tmp->refcount))
 			continue;
 
 		vlan = vlan_tmp;

net/batman-adv/types.h

@@ -746,7 +746,7 @@ struct batadv_softif_vlan {
 	atomic_t ap_isolation;		/* boolean */
 	struct batadv_vlan_tt tt;
 	struct hlist_node list;
-	atomic_t refcount;
+	struct kref refcount;
 	struct rcu_head rcu;
 };