netns: net_identifiers should be read_mostly

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/8021q/vlan.c b/net/8021q/vlan.c
index 39f8d01..d9cb020 100644
--- a/net/8021q/vlan.c
+++ b/net/8021q/vlan.c
@@ -41,7 +41,7 @@
 
 /* Global VLAN variables */
 
-int vlan_net_id;
+int vlan_net_id __read_mostly;
 
 /* Our listing of VLAN group(s) */
 static struct hlist_head vlan_group_hash[VLAN_GRP_HASH_SIZE];