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

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Date:   Sun, 11 Nov 2018 19:49:05 +0000
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, "Eric Dumazet" <edumazet@...gle.com>,
        "Pablo Neira Ayuso" <pablo@...filter.org>
Subject: [PATCH 3.16 150/366] netfilter: ipv6: nf_defrag: reduce struct
 net memory waste

3.16.61-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Eric Dumazet <edumazet@...gle.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@...gle.com>
Signed-off-by: Pablo Neira Ayuso <pablo@...filter.org>
Signed-off-by: Ben Hutchings <ben@...adent.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);
 }