batman-adv: Initialize lockdep class keys for hashes

The hash for claim and backbone hash in the bridge loop avoidance code receive
the same key because they are getting initialized by hash_new with the same
key. Lockdep will create a backtrace when they are used recursively. This can
be avoided by reinitializing the key directly after the hash_new.
Signed-off-by: Sven Eckelmann <sven@narfation.org>

net/batman-adv/bridge_loop_avoidance.c

@@ -1127,6 +1127,14 @@ static void bla_periodic_work(struct work_struct *work)
 	bla_start_timer(bat_priv);
 }
 
+/* The hash for claim and backbone hash receive the same key because they
+ * are getting initialized by hash_new with the same key. Reinitializing
+ * them with to different keys to allow nested locking without generating
+ * lockdep warnings
+ */
+static struct lock_class_key claim_hash_lock_class_key;
+static struct lock_class_key backbone_hash_lock_class_key;
+
 /* initialize all bla structures */
 int bla_init(struct bat_priv *bat_priv)
 {
@@ -1164,6 +1172,11 @@ int bla_init(struct bat_priv *bat_priv)
 	if (!bat_priv->claim_hash || !bat_priv->backbone_hash)
 		return -1;
 
+	batadv_hash_set_lock_class(bat_priv->claim_hash,
+				   &claim_hash_lock_class_key);
+	batadv_hash_set_lock_class(bat_priv->backbone_hash,
+				   &backbone_hash_lock_class_key);
+
 	bat_dbg(DBG_BLA, bat_priv, "bla hashes initialized\n");
 
 	bla_start_timer(bat_priv);

net/batman-adv/hash.c

@@ -69,3 +69,12 @@ struct hashtable_t *hash_new(uint32_t size)
 	kfree(hash);
 	return NULL;
 }
+
+void batadv_hash_set_lock_class(struct hashtable_t *hash,
+				struct lock_class_key *key)
+{
+	uint32_t i;
+
+	for (i = 0; i < hash->size; i++)
+		lockdep_set_class(&hash->list_locks[i], key);
+}

net/batman-adv/hash.h

@@ -45,6 +45,10 @@ struct hashtable_t {
 /* allocates and clears the hash */
 struct hashtable_t *hash_new(uint32_t size);
 
+/* set class key for all locks */
+void batadv_hash_set_lock_class(struct hashtable_t *hash,
+				struct lock_class_key *key);
+
 /* free only the hashtable and the hash itself. */
 void hash_destroy(struct hashtable_t *hash);