net: Convert ovs_net_ops

These pernet_operations initialize and destroy net_generic()
data pointed by ovs_net_id. Exit method destroys vports from
alive net to exiting net. Since they are only pernet_operations
interested in this data, and exit method is executed under
exclusive global lock (ovs_mutex), they are safe to be executed
in parallel.
Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/openvswitch/datapath.c

@@ -2384,6 +2384,7 @@ static struct pernet_operations ovs_net_ops = {
 	.exit = ovs_exit_net,
 	.id   = &ovs_net_id,
 	.size = sizeof(struct ovs_net),
+	.async = true,
 };
 
 static int __init dp_init(void)