[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>

2 files changed, 2 insertions, 2 deletions

diff --git a/net/sctp/ipv6.c b/net/sctp/ipv6.c
index fa3be2b8fb5f..15c05165c905 100644
--- a/net/sctp/ipv6.c
+++ b/net/sctp/ipv6.c
@@ -866,7 +866,7 @@ static int sctp_inet6_supported_addrs(const struct sctp_sock *opt,
         return 2;
 }
 
-static struct proto_ops inet6_seqpacket_ops = {
+static const struct proto_ops inet6_seqpacket_ops = {
         .family     = PF_INET6,
         .owner      = THIS_MODULE,
         .release    = inet6_release,
diff --git a/net/sctp/protocol.c b/net/sctp/protocol.c
index f775d78aa59d..d1b0747a5b9d 100644
--- a/net/sctp/protocol.c
+++ b/net/sctp/protocol.c
@@ -829,7 +829,7 @@ static struct notifier_block sctp_inetaddr_notifier = {
 };
 
 /* Socket operations.  */
-static struct proto_ops inet_seqpacket_ops = {
+static const struct proto_ops inet_seqpacket_ops = {
         .family      = PF_INET,
         .owner       = THIS_MODULE,
         .release     = inet_release,       /* Needs to be wrapped... */