batman-adv: use __dev_get_by_index instead of dev_get_by_index to find interface

The following call chains indicate that batadv_is_on_batman_iface()
is always under rtnl_lock protection as call_netdevice_notifier()
is protected by rtnl_lock. So if __dev_get_by_index() rather than
dev_get_by_index() is used to find interface handler in it, this
would help us avoid to change interface reference counter.

call_netdevice_notifier()
  batadv_hard_if_event()
    batadv_hardif_add_interface()
      batadv_is_valid_iface()
        batadv_is_on_batman_iface()

Cc: Antonio Quartulli <antonio@meshcoding.com>
Signed-off-by: Ying Xue <ying.xue@windriver.com>
Acked-by: Antonio Quartulli <antonio@meshcoding.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/batman-adv/hard-interface.c b/net/batman-adv/hard-interface.c
index 1b12573..3d417d3 100644 (file)
--- a/net/batman-adv/hard-interface.c
+++ b/net/batman-adv/hard-interface.c
@@ -87,15 +87,13 @@ static bool batadv_is_on_batman_iface(const struct net_device *net_dev)
                return false;
 
        /* recurse over the parent device */
-       parent_dev = dev_get_by_index(&init_net, net_dev->iflink);
+       parent_dev = __dev_get_by_index(&init_net, net_dev->iflink);
        /* if we got a NULL parent_dev there is something broken.. */
        if (WARN(!parent_dev, "Cannot find parent device"))
                return false;
 
        ret = batadv_is_on_batman_iface(parent_dev);
 
-       if (parent_dev)
-               dev_put(parent_dev);
        return ret;
 }