sctp: optimize the sctp_sysctl_net_register

Here, when the net is init_net, we needn't to kmemdup the ctl_table
again. So add a check for net. Also we can save some memory.
Signed-off-by: Wang Weidong <wangweidong1@huawei.com>
Acked-by: Neil Horman <nhorman@tuxdriver.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/sctp/sysctl.c

@@ -402,7 +402,9 @@ static int proc_sctp_do_rto_max(struct ctl_table *ctl, int write,
 
 int sctp_sysctl_net_register(struct net *net)
 {
-	struct ctl_table *table;
+	struct ctl_table *table = sctp_net_table;
+
+	if (!net_eq(net, &init_net)) {
 		int i;
 
 		table = kmemdup(sctp_net_table, sizeof(sctp_net_table), GFP_KERNEL);
@@ -411,6 +413,7 @@ int sctp_sysctl_net_register(struct net *net)
 
 		for (i = 0; table[i].data; i++)
 			table[i].data += (char *)(&net->sctp) - (char *)&init_net.sctp;
+	}
 
 	net->sctp.sysctl_header = register_net_sysctl(net, "net/sctp", table);
 	return 0;