From 74183a956dec832723b411ed8497f58d1fc84fec Mon Sep 17 00:00:00 2001
From: Jiayuan Chen <jiayuan.chen@shopee.com>
Date: Fri, 3 Jul 2026 14:38:24 +0800
Subject: [PATCH] mm: memcg: reset oom_group in css_reset

memory.oom.group defaults to disabled, but css_reset did not clear
memcg->oom_group when a disabled memory css is kept alive by another
controller dependency.

Reset it with the other memory controller policies so a hidden memcg
cannot keep applying stale group OOM kill policy.

Link: https://lore.kernel.org/20260703063826.306878-2-jiayuan.chen@linux.dev
Signed-off-by: Jiayuan Chen <jiayuan.chen@shopee.com>
Acked-by: Roman Gushchin <roman.gushchin@linux.dev>
Reviewed-by: Muchun Song <muchun.song@linux.dev>
Cc: Jiayuan Chen <jiayuan.chen@linux.dev>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Shakeel Butt <shakeel.butt@linux.dev>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---
 mm/memcontrol.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index c20ef3c1d6fe..c7de62c8f86f 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -4362,6 +4362,7 @@ static void mem_cgroup_css_reset(struct cgroup_subsys_state *css)
 
 	page_counter_set_max(&memcg->memory, PAGE_COUNTER_MAX);
 	page_counter_set_max(&memcg->swap, PAGE_COUNTER_MAX);
+	WRITE_ONCE(memcg->oom_group, false);
 #ifdef CONFIG_ZSWAP
 	WRITE_ONCE(memcg->zswap_max, PAGE_COUNTER_MAX);
 	WRITE_ONCE(memcg->zswap_writeback, true);