Re: [PATCH] mm: memcg-v1: fix memory.memsw.failcnt accounting

[Guopeng Zhang <guopeng.zhang@linux.dev>]

在 2026/8/11 03:09, Johannes Weiner 写道:
> On Mon, Aug 10, 2026 at 03:42:47PM +0800, Guopeng Zhang wrote:
>> From: Guopeng Zhang <zhangguopeng@kylinos.cn>
>>
>> Commit 0e2759afcaf9 ("page_counter: track failcnt only for legacy
>> cgroups") made failcnt accounting conditional on track_failcnt. It
>> enabled the flag for memcg->memory, but not for memcg->memsw.
>>
>> Consequently, memory.memsw.failcnt remains zero when the memory+swap
>> limit is hit. Enable failcnt accounting for the v1 memsw counter.
>>
>> Reproducer:
>>
>>     CG=/sys/fs/cgroup/memory/memsw-test
>>     LIMIT=33554432
>>     mkdir "$CG"
>>     echo "$LIMIT" > "$CG/memory.limit_in_bytes"
>>     echo "$LIMIT" > "$CG/memory.memsw.limit_in_bytes"
>>
>> Start a child process in the cgroup and make it allocate and touch 96 MiB
>> of memory, causing a memcg OOM.
>>
>>     cat "$CG/memory.memsw.failcnt"
>>
>> Without the patch, memory.memsw.failcnt is 0. With the patch,
>> memory.memsw.failcnt is greater than 0.
>>
>> Fixes: 0e2759afcaf9 ("page_counter: track failcnt only for legacy cgroups")
>> Signed-off-by: Guopeng Zhang <zhangguopeng@kylinos.cn>
> 
> Acked-by: Johannes Weiner <hannes@cmpxchg.org>
> 
> Sashiko raises a valid point. kmem.tcp.limit_in_bytes is deprecated
> and will warn if set, but the functionality is still there for the
> time being. No need to leave it broken until it's removed.
> 
> Could you add
> 
> 		memcg->tcpmem.track_failcnt = !memcg_on_dfl;
> 
> as well?

Thanks for the review and Ack.

Agreed. I'll add

    memcg->tcpmem.track_failcnt = !memcg_on_dfl;

and update the changelog accordingly in v2.

Thanks,
Guopeng

> 
>> ---
>>  mm/memcontrol.c | 1 +
>>  1 file changed, 1 insertion(+)
>>
>> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
>> index 6939a4fbb991..4ffe5b3733d9 100644
>> --- a/mm/memcontrol.c
>> +++ b/mm/memcontrol.c
>> @@ -4235,6 +4235,7 @@ mem_cgroup_css_alloc(struct cgroup_subsys_state *parent_css)
>>  #ifdef CONFIG_MEMCG_V1
>>  		WRITE_ONCE(memcg->swappiness, mem_cgroup_swappiness(parent));
>>  		memcg->memory.track_failcnt = !memcg_on_dfl;
>> +		memcg->memsw.track_failcnt = !memcg_on_dfl;
>>  		WRITE_ONCE(memcg->oom_kill_disable, READ_ONCE(parent->oom_kill_disable));
>>  		page_counter_init(&memcg->kmem, &parent->kmem, false);
>>  		page_counter_init(&memcg->tcpmem, &parent->tcpmem, false);