batman-adv: Use rcu_dereference_protected by update-side

Usually rcu_dereference isn't necessary in situations were the
RCU-protected data structure cannot change, but sparse and lockdep still
need a similar functionality for analysis. rcu_dereference_protected
implements the reduced version which should be used to support the
dynamic and static analysis.
Signed-off-by: Sven Eckelmann <sven@narfation.org>

net/batman-adv/gateway_client.c

@@ -86,7 +86,7 @@ static void gw_select(struct bat_priv *bat_priv, struct gw_node *new_gw_node)
 	if (new_gw_node && !atomic_inc_not_zero(&new_gw_node->refcount))
 		new_gw_node = NULL;
 
-	curr_gw_node = bat_priv->curr_gw;
+	curr_gw_node = rcu_dereference_protected(bat_priv->curr_gw, 1);
 	rcu_assign_pointer(bat_priv->curr_gw, new_gw_node);
 
 	if (curr_gw_node)

net/batman-adv/hard-interface.c

@@ -138,7 +138,7 @@ static void primary_if_select(struct bat_priv *bat_priv,
 	if (new_hard_iface && !atomic_inc_not_zero(&new_hard_iface->refcount))
 		new_hard_iface = NULL;
 
-	curr_hard_iface = bat_priv->primary_if;
+	curr_hard_iface = rcu_dereference_protected(bat_priv->primary_if, 1);
 	rcu_assign_pointer(bat_priv->primary_if, new_hard_iface);
 
 	if (curr_hard_iface)

net/batman-adv/soft-interface.c

@@ -241,7 +241,8 @@ static void softif_neigh_vid_select(struct bat_priv *bat_priv,
 	if (new_neigh && !atomic_inc_not_zero(&new_neigh->refcount))
 		new_neigh = NULL;
 
-	curr_neigh = softif_neigh_vid->softif_neigh;
+	curr_neigh = rcu_dereference_protected(softif_neigh_vid->softif_neigh,
+					       1);
 	rcu_assign_pointer(softif_neigh_vid->softif_neigh, new_neigh);
 
 	if ((curr_neigh) && (!new_neigh))