[PATCH 4/4] memcg: always enable kmemcg on the default hierarchy

[Tejun Heo <tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>]

On the default hierarchy, all memory consumption will be accounted
together and controlled by the same set of limits.  Always enable
kmemcg on the default hierarchy.

Signed-off-by: Tejun Heo <tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
---
 mm/memcontrol.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index c94b686..8a5dd01 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -4362,6 +4362,13 @@ mem_cgroup_css_online(struct cgroup_subsys_state *css)
 	if (ret)
 		return ret;
 
+	/* kmem is always accounted together on the default hierarchy */
+	if (cgroup_on_dfl(css->cgroup)) {
+		ret = memcg_activate_kmem(memcg, PAGE_COUNTER_MAX);
+		if (ret)
+			return ret;
+	}
+
 	/*
 	 * Make sure the memcg is initialized: mem_cgroup_iter()
 	 * orders reading memcg->initialized against its callers
-- 
2.4.3