mm: memcg: guard memcg1-specific members of struct mem_cgroup_per_node

Put memcg1-specific members of struct mem_cgroup_per_node under the
CONFIG_MEMCG_V1 config option.

Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Roman Gushchin <[email protected]>
Acked-by: Shakeel Butt <[email protected]>
Cc: Johannes Weiner <[email protected]>
Cc: Michal Hocko <[email protected]>
Cc: Muchun Song <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

include/linux/memcontrol.h

@@ -92,6 +92,7 @@ struct mem_cgroup_per_node {
 	struct lruvec_stats			*lruvec_stats;
 	struct shrinker_info __rcu	*shrinker_info;
 
+#ifdef CONFIG_MEMCG_V1
 	/*
 	 * Memcg-v1 only stuff in middle as buffer between read mostly fields
 	 * and update often fields to avoid false sharing. Once v1 stuff is
@@ -102,6 +103,7 @@ struct mem_cgroup_per_node {
 	unsigned long		usage_in_excess;/* Set to the value by which */
 						/* the soft limit is exceeded*/
 	bool			on_tree;
+#endif
 
 	/* Fields which get updated often at the end. */
 	struct lruvec		lruvec;