[PATCH V4 1/7] mm: memcontrol: add helper of memcg_get_e_css

[Ming Lei <ming.lei@redhat.com>]

And helper of memcg_get_e_css() so that the consumer needn't to
call cgroup_get_e_css(cgroup, &memory_cgrp_subsys) directly, since
&memory_cgrp_subsys has to be used in case that MEMCG is enabled.

Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
---
 include/linux/memcontrol.h | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index bfe5c486f4ad..741852addbd7 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -1101,6 +1101,11 @@ unsigned long mem_cgroup_soft_limit_reclaim(pg_data_t *pgdat, int order,
 						gfp_t gfp_mask,
 						unsigned long *total_scanned);
 
+static inline
+struct cgroup_subsys_state *memcg_get_e_css(struct cgroup_subsys_state *css)
+{
+	return cgroup_get_e_css(css->cgroup, &memory_cgrp_subsys);
+}
 #else /* CONFIG_MEMCG */
 
 #define MEM_CGROUP_ID_SHIFT	0
@@ -1456,6 +1461,11 @@ unsigned long mem_cgroup_soft_limit_reclaim(pg_data_t *pgdat, int order,
 {
 	return 0;
 }
+static inline
+struct cgroup_subsys_state *memcg_get_e_css(struct cgroup_subsys_state *css)
+{
+	return NULL;
+}
 #endif /* CONFIG_MEMCG */
 
 static inline void __inc_lruvec_kmem_state(void *p, enum node_stat_item idx)
-- 
2.31.1