[PATCH] mm/memcg: return -EBUSY when oom-kill-disable modified and memcg use_hierarchy, has children

[Wanpeng Li <liwp.linux@gmail.com>]

From: Wanpeng Li <liwp@linux.vnet.ibm.com>

When oom-kill-disable modified by the user and current memcg use_hierarchy,
the change can occur, provided the current memcg has no children. If it
has children, return -EBUSY is enough.

Signed-off-by: Wanpeng Li <liwp.linux@gmail.com>
---
 mm/memcontrol.c |    7 +++++--
 1 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 63e36e7..4b64fe0 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -4521,11 +4521,14 @@ static int mem_cgroup_oom_control_write(struct cgroup *cgrp,
 
 	cgroup_lock();
 	/* oom-kill-disable is a flag for subhierarchy. */
-	if ((parent->use_hierarchy) ||
-	    (memcg->use_hierarchy && !list_empty(&cgrp->children))) {
+	if (parent->use_hierarchy) {
 		cgroup_unlock();
 		return -EINVAL;
+	} else if (memcg->use_hierarchy && !list_empty(&cgrp->children)) {
+		cgroup_unlock();
+		return -EBUSY;
 	}
+
 	memcg->oom_kill_disable = val;
 	if (!val)
 		memcg_oom_recover(memcg);
-- 
1.7.5.4

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