[NET/IPV4/IPV6]: Change some sysctl variables to __read_mostly

Change net/core, ipv4 and ipv6 sysctl variables to __read_mostly.

Couldn't actually measure any performance increase while testing (.3%
I consider noise), but seems like the right thing to do.

Signed-off-by: Brian Haley <brian.haley@hp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
index 4af741e..f1ede90 100644
--- a/net/ipv6/addrconf.c
+++ b/net/ipv6/addrconf.c
@@ -146,7 +146,7 @@
 
 static ATOMIC_NOTIFIER_HEAD(inet6addr_chain);
 
-struct ipv6_devconf ipv6_devconf = {
+struct ipv6_devconf ipv6_devconf __read_mostly = {
 	.forwarding		= 0,
 	.hop_limit		= IPV6_DEFAULT_HOPLIMIT,
 	.mtu6			= IPV6_MIN_MTU,
@@ -177,7 +177,7 @@
 #endif
 };
 
-static struct ipv6_devconf ipv6_devconf_dflt = {
+static struct ipv6_devconf ipv6_devconf_dflt __read_mostly = {
 	.forwarding		= 0,
 	.hop_limit		= IPV6_DEFAULT_HOPLIMIT,
 	.mtu6			= IPV6_MIN_MTU,
@@ -3665,7 +3665,7 @@
 	ctl_table addrconf_conf_dir[2];
 	ctl_table addrconf_proto_dir[2];
 	ctl_table addrconf_root_dir[2];
-} addrconf_sysctl = {
+} addrconf_sysctl __read_mostly = {
 	.sysctl_header = NULL,
 	.addrconf_vars = {
         	{