Re: [PATCH] mm/mglru: restore accidentally removed seq < max_seq check

[Baolin Wang]

On 9/15/26 6:15 PM, Barry Song (Xiaomi) wrote:
> Since commit 798c0330c2ca ("mm/mglru: rework aging feedback"),
> the following sanity check was accidentally removed:
>         if (seq < max_seq)
>                 return 0;
>
> That means we can perform aging for any value less than or equal to
> max_gen_nr.
>
> This has been inconsistent with
> Documentation/admin-guide/mm/multigen_lru.rst, which states:
>
>   Users can write the following command to ``lru_gen`` to create a new
>   generation ``max_gen_nr+1``:
>
>       ``+ memcg_id node_id max_gen_nr [can_swap [force_scan]]``
>
> The correct semantics are that writing a value smaller than
> max_gen_nr should return 0, since the requested generation already
> exists.
>
> Fixes: 798c0330c2ca ("mm/mglru: rework aging feedback")
> Reported-by: Chuanhua Han <hanchuanhua802@xxxxxxxxx>
> Signed-off-by: Barry Song (Xiaomi) <baohua@xxxxxxxxxx>
> ---

LGTM.
Reviewed-by: Baolin Wang <baolin.wang@xxxxxxxxxxxxxxxxx>