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Subject[PATCH] net/tcp: Fix tcp memory limits initialization when !CONFIG_SYSCTL

ok, the patch works fine - in the tested version i've renamed
the function and cleaned up the changelog a bit, see the final
patch below.

Thanks,

Ingo

-------------------->
From c5b258533cb5f6f216522163a9aa7ff029dc390f Mon Sep 17 00:00:00 2001
From: Glauber Costa <glommer@parallels.com>
Date: Fri, 27 Jan 2012 20:27:06 +0400
Subject: [PATCH] net/tcp: Fix tcp memory limits initialization when !CONFIG_SYSCTL

sysctl_tcp_mem() initialization was moved to sysctl_tcp_ipv4.c
in commit 3dc43e3e4d0b52197d3205214fe8f162f9e0c334, since it
became a per-ns value.

That code, however, will never run when CONFIG_SYSCTL is
disabled, leading to bogus values on those fields - causing hung
TCP sockets.

This patch fixes it by keeping an initialization code in
tcp_init(). It will be overwritten by the first net namespace
init if CONFIG_SYSCTL is compiled in, and do the right thing if
it is compiled out.

It is also named properly as tcp_init_mem(), to properly signal
its non-sysctl side effect on TCP limits.

Reported-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Glauber Costa <glommer@parallels.com>
Cc: David S. Miller <davem@davemloft.net>
Link: http://lkml.kernel.org/r/4F22D05A.8030604@parallels.com
[ renamed the function, tidied up the changelog a bit ]
Signed-off-by: Ingo Molnar <mingo@elte.hu>
---
include/net/tcp.h | 2 ++
net/ipv4/sysctl_net_ipv4.c | 1 +
net/ipv4/tcp.c | 16 +++++++++++++---
3 files changed, 16 insertions(+), 3 deletions(-)

diff --git a/include/net/tcp.h b/include/net/tcp.h
index 0118ea9..d49db01 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -311,6 +311,8 @@ extern struct proto tcp_prot;
#define TCP_ADD_STATS_USER(net, field, val) SNMP_ADD_STATS_USER((net)->mib.tcp_statistics, field, val)
#define TCP_ADD_STATS(net, field, val) SNMP_ADD_STATS((net)->mib.tcp_statistics, field, val)

+extern void tcp_init_mem(struct net *net);
+
extern void tcp_v4_err(struct sk_buff *skb, u32);

extern void tcp_shutdown (struct sock *sk, int how);
diff --git a/net/ipv4/sysctl_net_ipv4.c b/net/ipv4/sysctl_net_ipv4.c
index 4aa7e9d..4cb9cd2 100644
--- a/net/ipv4/sysctl_net_ipv4.c
+++ b/net/ipv4/sysctl_net_ipv4.c
@@ -814,6 +814,7 @@ static __net_init int ipv4_sysctl_init_net(struct net *net)

net->ipv4.sysctl_rt_cache_rebuild_count = 4;

+ tcp_init_mem(net);
limit = nr_free_buffer_pages() / 8;
limit = max(limit, 128UL);
net->ipv4.sysctl_tcp_mem[0] = limit / 4 * 3;
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 9bcdec3..06373b4 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -3216,6 +3216,16 @@ static int __init set_thash_entries(char *str)
}
__setup("thash_entries=", set_thash_entries);

+void tcp_init_mem(struct net *net)
+{
+ /* Set per-socket limits to no more than 1/128 the pressure threshold */
+ unsigned long limit = nr_free_buffer_pages() / 8;
+ limit = max(limit, 128UL);
+ net->ipv4.sysctl_tcp_mem[0] = limit / 4 * 3;
+ net->ipv4.sysctl_tcp_mem[1] = limit;
+ net->ipv4.sysctl_tcp_mem[2] = net->ipv4.sysctl_tcp_mem[0] * 2;
+}
+
void __init tcp_init(void)
{
struct sk_buff *skb = NULL;
@@ -3276,9 +3286,9 @@ void __init tcp_init(void)
sysctl_tcp_max_orphans = cnt / 2;
sysctl_max_syn_backlog = max(128, cnt / 256);

- /* Set per-socket limits to no more than 1/128 the pressure threshold */
- limit = ((unsigned long)init_net.ipv4.sysctl_tcp_mem[1])
- << (PAGE_SHIFT - 7);
+ tcp_init_mem(&init_net);
+ limit = nr_free_buffer_pages() / 8;
+ limit = max(limit, 128UL);
max_share = min(4UL*1024*1024, limit);

sysctl_tcp_wmem[0] = SK_MEM_QUANTUM;

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