batman-adv: hash_add() has to discriminate on the return value

hash_add() returns 0 on success while returns -1 either on error and on
entry already present. The caller could use such information to select
its behaviour. For this reason it is useful that hash_add() returns -1
in case on error and returns 1 in case of entry already present.

Signed-off-by: Antonio Quartulli <ordex@autistici.org>
Signed-off-by: Marek Lindner <lindner_marek@yahoo.de>
diff --git a/net/batman-adv/vis.c b/net/batman-adv/vis.c
index 8a1b985..8b75cc5 100644
--- a/net/batman-adv/vis.c
+++ b/net/batman-adv/vis.c
@@ -465,7 +465,7 @@
 	/* try to add it */
 	hash_added = hash_add(bat_priv->vis_hash, vis_info_cmp, vis_info_choose,
 			      info, &info->hash_entry);
-	if (hash_added < 0) {
+	if (hash_added != 0) {
 		/* did not work (for some reason) */
 		kref_put(&info->refcount, free_info);
 		info = NULL;
@@ -920,7 +920,7 @@
 	hash_added = hash_add(bat_priv->vis_hash, vis_info_cmp, vis_info_choose,
 			      bat_priv->my_vis_info,
 			      &bat_priv->my_vis_info->hash_entry);
-	if (hash_added < 0) {
+	if (hash_added != 0) {
 		pr_err("Can't add own vis packet into hash\n");
 		/* not in hash, need to remove it manually. */
 		kref_put(&bat_priv->my_vis_info->refcount, free_info);