[NET]: move struct proto_ops to const

I noticed that some of 'struct proto_ops' used in the kernel may share
a cache line used by locks or other heavily modified data. (default
linker alignement is 32 bytes, and L1_CACHE_LINE is 64 or 128 at
least)

This patch makes sure a 'struct proto_ops' can be declared as const,
so that all cpus can share all parts of it without false sharing.

This is not mandatory : a driver can still use a read/write structure
if it needs to (and eventually a __read_mostly)

I made a global stubstitute to change all existing occurences to make
them const.

This should reduce the possibility of false sharing on SMP, and
speedup some socket system calls.

Signed-off-by: Eric Dumazet <dada1@cosmosbay.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 3 insertions, 3 deletions

diff --git a/net/ipv6/af_inet6.c b/net/ipv6/af_inet6.c
index 70a510ff31ee..7c9f19269f21 100644
--- a/net/ipv6/af_inet6.c
+++ b/net/ipv6/af_inet6.c
@@ -462,7 +462,7 @@ int inet6_ioctl(struct socket *sock, unsigned int cmd, unsigned long arg)
         return(0);
 }
 
-struct proto_ops inet6_stream_ops = {
+const struct proto_ops inet6_stream_ops = {
         .family =       PF_INET6,
         .owner =        THIS_MODULE,
         .release =      inet6_release,
@@ -483,7 +483,7 @@ struct proto_ops inet6_stream_ops = {
         .sendpage =     tcp_sendpage
 };
 
-struct proto_ops inet6_dgram_ops = {
+const struct proto_ops inet6_dgram_ops = {
         .family =       PF_INET6,
         .owner =        THIS_MODULE,
         .release =      inet6_release,
@@ -511,7 +511,7 @@ static struct net_proto_family inet6_family_ops = {
 };
 
 /* Same as inet6_dgram_ops, sans udp_poll.  */
-static struct proto_ops inet6_sockraw_ops = {
+static const struct proto_ops inet6_sockraw_ops = {
         .family =       PF_INET6,
         .owner =        THIS_MODULE,
         .release =      inet6_release,