net: Convert ip6_frags_ops

Exit methods calls inet_frags_exit_net() with global ip6_frags
as argument. So, after we make the pernet_operations async,
a pair of exit methods may be called to iterate this hash table.
Since there is inet_frag_worker(), which already may work
in parallel with inet_frags_exit_net(), and it can make the same
cleanup, that inet_frags_exit_net() does, it's safe. So we may
mark these pernet_operations as async.
Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv6/reassembly.c

@@ -733,6 +733,7 @@ static void __net_exit ipv6_frags_exit_net(struct net *net)
 static struct pernet_operations ip6_frags_ops = {
 	.init = ipv6_frags_init_net,
 	.exit = ipv6_frags_exit_net,
+	.async = true,
 };
 
 int __init ipv6_frag_init(void)