linux-kernel - Re: [PATCH 4/9] mm/z3fold: remove unneeded page_mapcount

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Date:   Wed, 2 Mar 2022 09:22:48 +0100
From:   Vitaly Wool <vitaly.wool@...sulko.com>
To:     Miaohe Lin <linmiaohe@...wei.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Linux-MM <linux-mm@...ck.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 4/9] mm/z3fold: remove unneeded page_mapcount_reset and ClearPagePrivate

On Sat, Feb 19, 2022 at 10:26 AM Miaohe Lin <linmiaohe@...wei.com> wrote:
>
> Page->page_type and PagePrivate are not used in z3fold. We should remove
> these confusing unneeded operations. The z3fold do these here is due to
> referring to zsmalloc's migration code which does need these operations.

Absolutely, thanks for pointing this out.

> Signed-off-by: Miaohe Lin <linmiaohe@...wei.com>

Reviewed-by: Vitaly Wool <vitaly.wool@...sulko.com>

> ---
>  mm/z3fold.c | 3 ---
>  1 file changed, 3 deletions(-)
>
> diff --git a/mm/z3fold.c b/mm/z3fold.c
> index eb89271aea83..2f848ea45b4d 100644
> --- a/mm/z3fold.c
> +++ b/mm/z3fold.c
> @@ -420,7 +420,6 @@ static void free_z3fold_page(struct page *page, bool headless)
>                 __ClearPageMovable(page);
>                 unlock_page(page);
>         }
> -       ClearPagePrivate(page);
>         __free_page(page);
>  }
>
> @@ -1635,7 +1634,6 @@ static int z3fold_page_migrate(struct address_space *mapping, struct page *newpa
>         INIT_LIST_HEAD(&new_zhdr->buddy);
>         new_mapping = page_mapping(page);
>         __ClearPageMovable(page);
> -       ClearPagePrivate(page);
>
>         get_page(newpage);
>         z3fold_page_lock(new_zhdr);
> @@ -1655,7 +1653,6 @@ static int z3fold_page_migrate(struct address_space *mapping, struct page *newpa
>
>         queue_work_on(new_zhdr->cpu, pool->compact_wq, &new_zhdr->work);
>
> -       page_mapcount_reset(page);
>         clear_bit(PAGE_CLAIMED, &page->private);
>         put_page(page);
>         return 0;
> --
> 2.23.0
>