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: <c2551c48-3123-453f-bcb6-e6505b2d72da@linux.alibaba.com>
Date: Fri, 16 May 2025 09:33:03 +0800
From: Baolin Wang <baolin.wang@...ux.alibaba.com>
To: Kemeng Shi <shikemeng@...weicloud.com>, hughd@...gle.com,
 akpm@...ux-foundation.org
Cc: 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 2025/5/15 23:47, Kemeng Shi 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>

LGTM.
Reviewed-by: Baolin Wang <baolin.wang@...ux.alibaba.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;