batman-adv: Store modification counter via hash helpers

Multiple datastructures use the hash helper functions to add and remove
entries from the simple hlist based hashes. These are often also dumped to
userspace via netlink and thus should have a generation sequence counter.
Reported-by: Matthias Schiffer <mschiffer@universe-factory.net>
Signed-off-by: Sven Eckelmann <sven@narfation.org>
Signed-off-by: Simon Wunderlich <sw@simonwunderlich.de>

net/batman-adv/hash.c

@@ -32,6 +32,8 @@ static void batadv_hash_init(struct batadv_hashtable *hash)
 		INIT_HLIST_HEAD(&hash->table[i]);
 		spin_lock_init(&hash->list_locks[i]);
 	}
+
+	atomic_set(&hash->generation, 0);
 }
 
 /**

net/batman-adv/hash.h

@@ -21,6 +21,7 @@
 
 #include "main.h"
 
+#include <linux/atomic.h>
 #include <linux/compiler.h>
 #include <linux/list.h>
 #include <linux/rculist.h>
@@ -58,6 +59,9 @@ struct batadv_hashtable {
 
 	/** @size: size of hashtable */
 	u32 size;
+
+	/** @generation: current (generation) sequence number */
+	atomic_t generation;
 };
 
 /* allocates and clears the hash */
@@ -112,6 +116,7 @@ static inline int batadv_hash_add(struct batadv_hashtable *hash,
 
 	/* no duplicate found in list, add new element */
 	hlist_add_head_rcu(data_node, head);
+	atomic_inc(&hash->generation);
 
 	ret = 0;
 
@@ -154,6 +159,7 @@ static inline void *batadv_hash_remove(struct batadv_hashtable *hash,
 
 		data_save = node;
 		hlist_del_rcu(node);
+		atomic_inc(&hash->generation);
 		break;
 	}
 	spin_unlock_bh(&hash->list_locks[index]);