Re: [PATCH mm-new v2] mm: vmscan: put rotation-missed folios at the LRU tail

[Barry Song]

On Sun, Sep 20, 2026 at 9:25 PM Ridong Chen <ridong.chen@xxxxxxxxx> wrote:
>
[...]
>
>  mm/vmscan.c | 24 ++++++++++++++++++------
>  1 file changed, 18 insertions(+), 6 deletions(-)
>
> diff --git a/mm/vmscan.c b/mm/vmscan.c
> index e200ce3eb056..91295070ca33 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -1971,7 +1971,7 @@ static bool too_many_isolated(struct pglist_data *pgdat, int file,
>   *
>   * Note: The caller must not hold any lruvec lock.
>   */
> -static unsigned int move_folios_to_lru(struct list_head *list)
> +static unsigned int move_folios_to_lru(struct list_head *list, bool do_rotate)
>  {
>         int nr_pages, nr_moved = 0;
>         struct lruvec *lruvec = NULL;
> @@ -2018,7 +2018,19 @@ static unsigned int move_folios_to_lru(struct list_head *list)
>                         continue;
>                 }
>
> -               lruvec_add_folio(lruvec, folio);
> +               /*
> +                * Put clean, unreferenced and unpinned folios that may have
> +                * missed folio_rotate_reclaimable() at the tail to avoid
> +                * cold/hot inversion.
> +                */
> +               if (do_rotate && !folio_test_active(folio) && !folio_mapped(folio) &&
> +                   !folio_test_dirty(folio) && !folio_test_writeback(folio) &&
> +                   !folio_test_referenced(folio) &&
> +                   folio_ref_count(folio) == folio_expected_ref_count(folio))


I guess this is wrong. We hold an extra reference while isolating
the folio, so I think this should be:

`folio_ref_count(folio) == folio_expected_ref_count(folio) + 1`

Am I missing something here?

Best Regards
Barry