linux-kernel - Re: [PATCH v2] mm: do not try to migrate lru_gen if it's not associated with a memcg

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Date:   Mon, 16 Jan 2023 18:09:52 +0100
From:   David Hildenbrand <david@...hat.com>
To:     Yu Zhao <yuzhao@...gle.com>, msizanoen1 <msizanoen@...labs.xyz>
Cc:     Andrew Morton <akpm@...ux-foundation.org>, stable@...r.kernel.org,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] mm: do not try to migrate lru_gen if it's not
 associated with a memcg

On 16.01.23 00:13, Yu Zhao wrote:
> On Sun, Jan 15, 2023 at 6:47 AM msizanoen1 <msizanoen@...labs.xyz> wrote:
>>
>> In some cases, memory cgroup migration can be initiated by userspace
>> right after a process was created and right before `lru_gen_add_mm()` is
>> called (e.g. by some program watching a cgroup and moving away any
>> processes it detects[1]), which results in the following sequence of
>> WARNs followed by an Oops as the kernel attempts to perform a
>> `lru_gen_add_mm()` twice on the same `mm`:
> 
> ...
> 
>> Fix this by simply leaving the lru_gen alone if it has not been
>> associated with a memcg yet, as it should eventually be assigned to the
>> right cgroup anyway.
>>
>> [1]: https://gitlab.freedesktop.org/benzea/uresourced/-/blob/master/cgroupify/cgroupify.c
>>
>> v2:
>>          Added stable cc tags
>>
>> Signed-off-by: N/A (patch should not be copyrightable)
>> Cc: stable@...r.kernel.org
> 
> Thanks for the fix.  Cc'ing stable is the right thing to do. The
> commit message and the comment styles could be easily adjusted to
> align with the guidelines.
> 
> I don't think the N/A is acceptible though. I fully respect it if you
> wish to remain anonymous -- I can send a similar fix crediting you
> as the "anonymous user <msizanoen@...labs.xyz>" who reported this bug.

Not acceptable:

Documentation/process/submitting-patches.rs

"using your real name (sorry, no pseudonyms or anonymous contributions.)"


-- 
Thanks,

David / dhildenb