bridge: use exit_batch_rtnl() method

exit_batch_rtnl() is called while RTNL is held,
and devices to be unregistered can be queued in the dev_kill_list.

This saves one rtnl_lock()/rtnl_unlock() pair per netns
and one unregister_netdevice_many() call.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Antoine Tenart <atenart@kernel.org>
Link: https://lore.kernel.org/r/20240206144313.2050392-16-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

net/bridge/br.c

@@ -356,26 +356,21 @@ void br_opt_toggle(struct net_bridge *br, enum net_bridge_opts opt, bool on)
 		clear_bit(opt, &br->options);
 }
 
-static void __net_exit br_net_exit_batch(struct list_head *net_list)
+static void __net_exit br_net_exit_batch_rtnl(struct list_head *net_list,
+					      struct list_head *dev_to_kill)
 {
 	struct net_device *dev;
 	struct net *net;
-	LIST_HEAD(list);
-
-	rtnl_lock();
 
+	ASSERT_RTNL();
 	list_for_each_entry(net, net_list, exit_list)
 		for_each_netdev(net, dev)
 			if (netif_is_bridge_master(dev))
-				br_dev_delete(dev, &list);
-
-	unregister_netdevice_many(&list);
-
-	rtnl_unlock();
+				br_dev_delete(dev, dev_to_kill);
 }
 
 static struct pernet_operations br_net_ops = {
-	.exit_batch	= br_net_exit_batch,
+	.exit_batch_rtnl = br_net_exit_batch_rtnl,
 };
 
 static const struct stp_proto br_stp_proto = {