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

[Baolin Wang <baolin.wang@linux.alibaba.com>]

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@huaweicloud.com>

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