[PATCH v3 2/4] memcg: bail out memory.max when memcg is dying

[Jiayuan Chen <jiayuan.chen@linux.dev>]

From: Jiayuan Chen <jiayuan.chen@shopee.com>

memory.max has the same high-latency reclaim loop as memory.high, and
may additionally invoke the OOM killer on a cgroup that is already going
away, further delaying its removal.

Mitigate this by bailing out of the loop once memcg_is_dying().

Cc: Jiayuan Chen <jiayuan.chen@linux.dev>
Reported-by: Zhou Yingfu <yingfu.zhou@shopee.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Jiayuan Chen <jiayuan.chen@shopee.com>
---
 mm/memcontrol.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 4519dc9eae33..938f190a98fe 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -4849,6 +4849,10 @@ static ssize_t memory_max_write(struct kernfs_open_file *of,
 		if (signal_pending(current))
 			break;
 
+		/* cgroup_rmdir() waits for us with cgroup_mutex held. */
+		if (memcg_is_dying(memcg))
+			break;
+
 		if (!drained) {
 			drain_all_stock(memcg);
 			drained = true;
-- 
2.43.0