batman-adv: Less function calls in batadv_is_ap_isolated() after error detection

The variables "tt_local_entry" and "tt_global_entry" were eventually
checked again despite of a corresponding null pointer test before.

* Avoid this double check by reordering a function call sequence
  and the better selection of jump targets.

* Omit the initialisation for these variables at the beginning then.
Signed-off-by: Markus Elfring <elfring@users.sourceforge.net>
Signed-off-by: Sven Eckelmann <sven@narfation.org>
Signed-off-by: Simon Wunderlich <sw@simonwunderlich.de>

net/batman-adv/translation-table.c

@@ -3835,8 +3835,8 @@ void batadv_tt_local_commit_changes(struct batadv_priv *bat_priv)
 bool batadv_is_ap_isolated(struct batadv_priv *bat_priv, u8 *src, u8 *dst,
 			   unsigned short vid)
 {
-	struct batadv_tt_local_entry *tt_local_entry = NULL;
-	struct batadv_tt_global_entry *tt_global_entry = NULL;
+	struct batadv_tt_local_entry *tt_local_entry;
+	struct batadv_tt_global_entry *tt_global_entry;
 	struct batadv_softif_vlan *vlan;
 	bool ret = false;
 
@@ -3845,27 +3845,24 @@ bool batadv_is_ap_isolated(struct batadv_priv *bat_priv, u8 *src, u8 *dst,
 		return false;
 
 	if (!atomic_read(&vlan->ap_isolation))
-		goto out;
+		goto vlan_put;
 
 	tt_local_entry = batadv_tt_local_hash_find(bat_priv, dst, vid);
 	if (!tt_local_entry)
-		goto out;
+		goto vlan_put;
 
 	tt_global_entry = batadv_tt_global_hash_find(bat_priv, src, vid);
 	if (!tt_global_entry)
-		goto out;
-
-	if (!_batadv_is_ap_isolated(tt_local_entry, tt_global_entry))
-		goto out;
+		goto local_entry_put;
 
-	ret = true;
+	if (_batadv_is_ap_isolated(tt_local_entry, tt_global_entry))
+		ret = true;
 
-out:
+	batadv_tt_global_entry_put(tt_global_entry);
+local_entry_put:
+	batadv_tt_local_entry_put(tt_local_entry);
+vlan_put:
 	batadv_softif_vlan_put(vlan);
-	if (tt_global_entry)
-		batadv_tt_global_entry_put(tt_global_entry);
-	if (tt_local_entry)
-		batadv_tt_local_entry_put(tt_local_entry);
 	return ret;
 }