kselftests: memcg: update the oom group leaf events test

Patch series "mm: memcg kselftests fixes".


This patch (of 4):

Commit 9852ae3f ("mm, memcg: consider subtrees in memory.events") made
memory.events recursive: all events are propagated upwards by the tree. 
It was a change in semantics.

It broke the oom group leaf events test: it assumes that after an OOM the
oom_kill counter is zero on parent's level.

Let's adjust the test: it should have similar expectations for the child
and parent levels.

The test passes after this fix.

Link: https://lkml.kernel.org/r/20220415000133.3955987-2-roman.gushchin@linux.dev
Link: https://lkml.kernel.org/r/20220415000133.3955987-1-roman.gushchin@linux.devSigned-off-by: Roman Gushchin <roman.gushchin@linux.dev>
Reviewed-by: David Vernet <void@manifault.com>
Cc: Chris Down <chris@chrisdown.name>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Zefan Li <lizefan.x@bytedance.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

tools/testing/selftests/cgroup/test_memcontrol.c

@@ -1079,7 +1079,8 @@ static int test_memcg_sock(const char *root)
 /*
  * This test disables swapping and tries to allocate anonymous memory
  * up to OOM with memory.group.oom set. Then it checks that all
- * processes in the leaf (but not the parent) were killed.
+ * processes in the leaf were killed. It also checks that oom_events
+ * were propagated to the parent level.
  */
 static int test_memcg_oom_group_leaf_events(const char *root)
 {
@@ -1122,7 +1123,7 @@ static int test_memcg_oom_group_leaf_events(const char *root)
 	if (cg_read_key_long(child, "memory.events", "oom_kill ") <= 0)
 		goto cleanup;
 
-	if (cg_read_key_long(parent, "memory.events", "oom_kill ") != 0)
+	if (cg_read_key_long(parent, "memory.events", "oom_kill ") <= 0)
 		goto cleanup;
 
 	ret = KSFT_PASS;