Re: [PATCH] netfilter: nf_conntrack: Batch cleanup

The patch introduces nf_conntrack_cleanup_net_list(), which cleanups
nf_conntrack for a list of netns and calls synchronize_net() only once
for them all. This should reduce netns destruction time.
--
I've measured cleanup time for 1k dummy net ns. Here are the results:

 <without the patch>
 # modprobe nf_conntrack
 # time modprobe -r nf_conntrack

 real	0m10.337s
 user	0m0.000s
 sys	0m0.376s

 <with the patch>
 # modprobe nf_conntrack
 # time modprobe -r nf_conntrack

 real    0m5.661s
 user    0m0.000s
 sys     0m0.216s

Signed-off-by: Vladimir Davydov <redacted>
Cc: Patrick McHardy <redacted>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: "Eric W. Biederman" <redacted>
---
 include/net/netfilter/nf_conntrack_core.h |    1 +
 net/netfilter/nf_conntrack_core.c         |   46 ++++++++++++++++++++---------
 net/netfilter/nf_conntrack_standalone.c   |   16 ++++++----
 3 files changed, 43 insertions(+), 20 deletions(-)

diff --git a/include/net/netfilter/nf_conntrack_core.h b/include/net/netfilter/nf_conntrack_core.h
index 930275f..fb2b623 100644
--- a/include/net/netfilter/nf_conntrack_core.h
+++ b/include/net/netfilter/nf_conntrack_core.h

@@ -27,6 +27,7 @@ extern unsigned int nf_conntrack_in(struct net *net,
 
 extern int nf_conntrack_init_net(struct net *net);
 extern void nf_conntrack_cleanup_net(struct net *net);
+extern void nf_conntrack_cleanup_net_list(struct list_head *net_exit_list);
 
 extern int nf_conntrack_proto_pernet_init(struct net *net);
 extern void nf_conntrack_proto_pernet_fini(struct net *net);

diff --git a/net/netfilter/nf_conntrack_core.c b/net/netfilter/nf_conntrack_core.c
index c8e001a..09c02ef 100644
--- a/net/netfilter/nf_conntrack_core.c
+++ b/net/netfilter/nf_conntrack_core.c

@@ -1364,30 +1364,48 @@ void nf_conntrack_cleanup_end(void)
  */
 void nf_conntrack_cleanup_net(struct net *net)
 {
+	LIST_HEAD(single);
+
+	list_add(&net->exit_list, &single);
+	nf_conntrack_cleanup_net_list(&single);
+}
+