xfrm: avoid synchronize_rcu during netns destruction

Use the new exit_pre hook to NULL the netlink socket.
The net namespace core will do a synchronize_rcu() between the exit_pre
and exit/exit_batch handlers.

Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>

diff --git a/net/xfrm/xfrm_user.c b/net/xfrm/xfrm_user.c
index df8bc8fc724cc5e32be0c66c8b45a2f5345d266c..f0aecee4d5392f24b4bacb366ea728d823aa50a7 100644 (file)
--- a/net/xfrm/xfrm_user.c
+++ b/net/xfrm/xfrm_user.c
@@ -3480,18 +3480,22 @@ static int __net_init xfrm_user_net_init(struct net *net)
        return 0;
 }
 
+static void __net_exit xfrm_user_net_pre_exit(struct net *net)
+{
+       RCU_INIT_POINTER(net->xfrm.nlsk, NULL);
+}
+
 static void __net_exit xfrm_user_net_exit(struct list_head *net_exit_list)
 {
        struct net *net;
-       list_for_each_entry(net, net_exit_list, exit_list)
-               RCU_INIT_POINTER(net->xfrm.nlsk, NULL);
-       synchronize_net();
+
        list_for_each_entry(net, net_exit_list, exit_list)
                netlink_kernel_release(net->xfrm.nlsk_stash);
 }
 
 static struct pernet_operations xfrm_user_net_ops = {
        .init       = xfrm_user_net_init,
+       .pre_exit   = xfrm_user_net_pre_exit,
        .exit_batch = xfrm_user_net_exit,
 };