[BUGFIX][PATCH] memcg: fix thresholds with use_hierarchy == 1

[Kirill A. Shutsemov]

From: Kirill A. Shutemov <kirill@xxxxxxxxxxxxx>

We need to check parent's thresholds if parent has use_hierarchy == 1 to
be sure that parent's threshold events will be triggered even if parent
itself is not active (no MEM_CGROUP_EVENTS).

Signed-off-by: Kirill A. Shutemov <kirill@xxxxxxxxxxxxx>
---
 mm/memcontrol.c |   17 ++++++++++++++---
 1 files changed, 14 insertions(+), 3 deletions(-)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 3eed583..196f710 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -3587,9 +3587,20 @@ unlock:
 
 static void mem_cgroup_threshold(struct mem_cgroup *memcg)
 {
-	__mem_cgroup_threshold(memcg, false);
-	if (do_swap_account)
-		__mem_cgroup_threshold(memcg, true);
+	struct cgroup *parent;
+
+	while (1) {
+		__mem_cgroup_threshold(memcg, false);
+		if (do_swap_account)
+			__mem_cgroup_threshold(memcg, true);
+
+		parent = memcg->css.cgroup->parent;
+		if (!parent)
+			break;
+		memcg = mem_cgroup_from_cont(parent);
+		if (!memcg->use_hierarchy)
+			break;
+	}
 }
 
 static int compare_thresholds(const void *a, const void *b)
-- 
1.7.2.3

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