[PATCH 3.16 150/366] netfilter: ipv6: nf_defrag: reduce struct net memory waste

Ben Hutchings
2018-11-12T06:05:17Z

From: Eric Dumazet <edumazet@google.com>

commit 9ce7bc036ae4cfe3393232c86e9e1fea2153c237 upstream.

It is a waste of memory to use a full "struct netns_sysctl_ipv6"
while only one pointer is really used, considering netns_sysctl_ipv6
keeps growing.

Also, since "struct netns_frags" has cache line alignment,
it is better to move the frags_hdr pointer outside, otherwise
we spend a full cache line for this pointer.

This saves 192 bytes of memory per netns.

Fixes: c038a767cd69 ("ipv6: add a new namespace for nf_conntrack_reasm")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
include/net/net_namespace.h | 1 +
include/net/netns/ipv6.h | 1 -
net/ipv6/netfilter/nf_conntrack_reasm.c | 6 +++---
3 files changed, 4 insertions(+), 4 deletions(-)

--- a/include/net/net_namespace.h
+++ b/include/net/net_namespace.h
@@ -112,6 +112,7 @@ struct net {
#endif
#if IS_ENABLED(CONFIG_NF_DEFRAG_IPV6)
struct netns_nf_frag nf_frag;
+ struct ctl_table_header *nf_frag_frags_hdr;
#endif
struct sock *nfnl;
struct sock *nfnl_stash;
--- a/include/net/netns/ipv6.h
+++ b/include/net/netns/ipv6.h
@@ -80,7 +80,6 @@ struct netns_ipv6 {

#if IS_ENABLED(CONFIG_NF_DEFRAG_IPV6)
struct netns_nf_frag {
- struct netns_sysctl_ipv6 sysctl;
struct netns_frags frags;
};
#endif
--- a/net/ipv6/netfilter/nf_conntrack_reasm.c
+++ b/net/ipv6/netfilter/nf_conntrack_reasm.c
@@ -109,7 +109,7 @@ static int nf_ct_frag6_sysctl_register(s
if (hdr == NULL)
goto err_reg;

- net->nf_frag.sysctl.frags_hdr = hdr;
+ net->nf_frag_frags_hdr = hdr;
return 0;

err_reg:
@@ -123,8 +123,8 @@ static void __net_exit nf_ct_frags6_sysc
{
struct ctl_table *table;

- table = net->nf_frag.sysctl.frags_hdr->ctl_table_arg;
- unregister_net_sysctl_table(net->nf_frag.sysctl.frags_hdr);
+ table = net->nf_frag_frags_hdr->ctl_table_arg;
+ unregister_net_sysctl_table(net->nf_frag_frags_hdr);
if (!net_eq(net, &init_net))
kfree(table);
}