linux-kernel - Re: [PATCH 1/2] mm: vmscan: remove folio_test

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Message-ID: <qe56xt2natnxnkht7wgknsb5nqjhinaaajomvvvgnfpwry2jih@hsj2w5zqj6wv>
Date: Fri, 12 Sep 2025 09:13:04 -0700
From: Shakeel Butt <shakeel.butt@...ux.dev>
To: Baolin Wang <baolin.wang@...ux.alibaba.com>
Cc: akpm@...ux-foundation.org, hannes@...xchg.org, david@...hat.com, 
	mhocko@...nel.org, zhengqi.arch@...edance.com, lorenzo.stoakes@...cle.com, 
	hughd@...gle.com, willy@...radead.org, linux-mm@...ck.org, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] mm: vmscan: remove folio_test_private() check in
 pageout()

On Fri, Sep 12, 2025 at 11:45:07AM +0800, Baolin Wang wrote:
> Currently, we no longer attempt to write back filesystem folios in pageout(),
> and only tmpfs/shmem folios and anonymous swapcache folios can be written back.
> Moreover, tmpfs/shmem and swapcache folios do not use the PG_private flag,
> which means no fs-private private data is used. Therefore, we can remove the
> redundant folio_test_private() checks and related buffer_head release logic.
> 
> Signed-off-by: Baolin Wang <baolin.wang@...ux.alibaba.com>
> ---
>  mm/vmscan.c | 16 +---------------
>  1 file changed, 1 insertion(+), 15 deletions(-)
> 
> diff --git a/mm/vmscan.c b/mm/vmscan.c
> index f1fc36729ddd..8056fccb9cc4 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -697,22 +697,8 @@ static pageout_t pageout(struct folio *folio, struct address_space *mapping,
>  	 * swap_backing_dev_info is bust: it doesn't reflect the
>  	 * congestion state of the swapdevs.  Easy to fix, if needed.
>  	 */
> -	if (!is_page_cache_freeable(folio))
> +	if (!is_page_cache_freeable(folio) || !mapping)
>  		return PAGE_KEEP;
> -	if (!mapping) {
> -		/*
> -		 * Some data journaling orphaned folios can have
> -		 * folio->mapping == NULL while being dirty with clean buffers.
> -		 */

Can this case not happen anymore and try_to_free_buffers is not needed?

> -		if (folio_test_private(folio)) {
> -			if (try_to_free_buffers(folio)) {
> -				folio_clear_dirty(folio);
> -				pr_info("%s: orphaned folio\n", __func__);
> -				return PAGE_CLEAN;
> -			}
> -		}
> -		return PAGE_KEEP;
> -	}
>  
>  	if (!shmem_mapping(mapping) && !folio_test_anon(folio))
>  		return PAGE_ACTIVATE;
> -- 
> 2.43.7
>