batman-adv: Convert batadv_nc_node 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/network-coding.c

@@ -32,6 +32,7 @@
 #include <linux/jhash.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>
@@ -209,23 +210,26 @@ void batadv_nc_init_orig(struct batadv_orig_node *orig_node)
 /**
  * batadv_nc_node_release - release nc_node from lists and queue for free after
  *  rcu grace period
- * @nc_node: the nc node to free
+ * @ref: kref pointer of the nc_node
  */
-static void batadv_nc_node_release(struct batadv_nc_node *nc_node)
+static void batadv_nc_node_release(struct kref *ref)
 {
+	struct batadv_nc_node *nc_node;
+
+	nc_node = container_of(ref, struct batadv_nc_node, refcount);
+
 	batadv_orig_node_free_ref(nc_node->orig_node);
 	kfree_rcu(nc_node, rcu);
 }
 
 /**
- * batadv_nc_node_free_ref - decrement the nc node refcounter and possibly
+ * batadv_nc_node_free_ref - decrement the nc_node refcounter and possibly
  *  release it
- * @nc_node: the nc node to free
+ * @nc_node: nc_node to be free'd
  */
 static void batadv_nc_node_free_ref(struct batadv_nc_node *nc_node)
 {
-	if (atomic_dec_and_test(&nc_node->refcount))
-		batadv_nc_node_release(nc_node);
+	kref_put(&nc_node->refcount, batadv_nc_node_release);
 }
 
 /**
@@ -797,7 +801,7 @@ static struct batadv_nc_node
 		if (!batadv_compare_eth(nc_node->addr, orig_node->orig))
 			continue;
 
-		if (!atomic_inc_not_zero(&nc_node->refcount))
+		if (!kref_get_unless_zero(&nc_node->refcount))
 			continue;
 
 		/* Found a match */
@@ -848,7 +852,8 @@ static struct batadv_nc_node
 	INIT_LIST_HEAD(&nc_node->list);
 	ether_addr_copy(nc_node->addr, orig_node->orig);
 	nc_node->orig_node = orig_neigh_node;
-	atomic_set(&nc_node->refcount, 2);
+	kref_init(&nc_node->refcount);
+	kref_get(&nc_node->refcount);
 
 	/* Select ingoing or outgoing coding node */
 	if (in_coding) {

net/batman-adv/types.h

@@ -1067,7 +1067,7 @@ struct batadv_tt_roam_node {
 struct batadv_nc_node {
 	struct list_head list;
 	u8 addr[ETH_ALEN];
-	atomic_t refcount;
+	struct kref refcount;
 	struct rcu_head rcu;
 	struct batadv_orig_node *orig_node;
 	unsigned long last_seen;