linux-kernel - Re: [PATCH v2 4/5] mm: shmem: only remove inode from swaplist when it's swapped page count is 0

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Message-ID: <CAMgjq7Dz3yvZdMCr86OmxSUo2Xjd+ZG0-D4jBiLGXmYKcZZSTQ@mail.gmail.com>
Date: Fri, 16 May 2025 15:46:27 +0800
From: Kairui Song <ryncsn@...il.com>
To: Kemeng Shi <shikemeng@...weicloud.com>
Cc: hughd@...gle.com, baolin.wang@...ux.alibaba.com, akpm@...ux-foundation.org, 
	linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 4/5] mm: shmem: only remove inode from swaplist when
 it's swapped page count is 0

On Thu, May 15, 2025 at 2:54 PM Kemeng Shi <shikemeng@...weicloud.com> wrote:
>
> Even if we fail to allocate a swap entry, the inode might have previously
> allocated entry and we might take inode containing swap entry off swaplist.
> As a result, try_to_unuse() may enter a potential dead loop to repeatedly
> look for inode and clean it's swap entry.
> Only take inode off swaplist when it's swapped page count is 0 to fix the
> issue.
>
> Fixes: b487a2da3575b ("mm, swap: simplify folio swap allocation")
> Signed-off-by: Kemeng Shi <shikemeng@...weicloud.com>
> ---
>  mm/shmem.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/mm/shmem.c b/mm/shmem.c
> index aeeddf612baa..07b8e1400c67 100644
> --- a/mm/shmem.c
> +++ b/mm/shmem.c
> @@ -1651,8 +1651,8 @@ static int shmem_writepage(struct page *page, struct writeback_control *wbc)
>                 BUG_ON(folio_mapped(folio));
>                 return swap_writepage(&folio->page, wbc);
>         }
> -
> -       list_del_init(&info->swaplist);
> +       if (!info->swapped)
> +               list_del_init(&info->swaplist);
>         mutex_unlock(&shmem_swaplist_mutex);
>         if (nr_pages > 1)
>                 goto try_split;
> --
> 2.30.0
>
>

Thanks for the fix!

Reviewed-by: Kairui Song <kasong@...cent.com>