net: Convert rpcsec_gss_net_ops

These pernet_operations initialize and destroy sunrpc_net_id
refered per-net items. Only used global list is cache_list,
and accesses already serialized.

sunrpc_destroy_cache_detail() check for list_empty() without
cache_list_lock, but when it's called from unregister_pernet_subsys(),
there can't be callers in parallel, so we won't miss list_empty()
in this case.
Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com>
Acked-by: Anna Schumaker <Anna.Schumaker@netapp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/sunrpc/auth_gss/auth_gss.c

@@ -2063,6 +2063,7 @@ static __net_exit void rpcsec_gss_exit_net(struct net *net)
 static struct pernet_operations rpcsec_gss_net_ops = {
 	.init = rpcsec_gss_init_net,
 	.exit = rpcsec_gss_exit_net,
+	.async = true,
 };
 
 /*