linux-kernel - Re: [PATCH RESEND] mm/vmscan: remove redundant folio_test

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Message-ID: <CAG18JnwT1P6W6AwQX0nKDiGTBtObzVXNO7RgO2B-ipnC3D4xGg@mail.gmail.com>
Date: Tue, 12 Aug 2025 03:21:12 +0800
From: Jialin Wang <wjl.linux@...il.com>
To: Harry Yoo <harry.yoo@...cle.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>, Johannes Weiner <hannes@...xchg.org>, 
	David Hildenbrand <david@...hat.com>, Michal Hocko <mhocko@...nel.org>, 
	Qi Zheng <zhengqi.arch@...edance.com>, Shakeel Butt <shakeel.butt@...ux.dev>, 
	Lorenzo Stoakes <lorenzo.stoakes@...cle.com>, linux-mm@...ck.org, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH RESEND] mm/vmscan: remove redundant folio_test_swapbacked()

On Tue, Aug 12, 2025 at 2:53 AM Harry Yoo <harry.yoo@...cle.com> wrote:
>
> This is marked as RESEND, but which patch is it a resend of?
> I can’t find the original one.
>
I sent the original one to the wrong mailing list and missed proper cc's, sorry.
https://lore.kernel.org/lkml/20250811181839.40336-1-wjl.linux@gmail.com/

> On Tue, Aug 12, 2025 at 02:25:00AM +0800, Jialin Wang wrote:
> > When !folio_is_file_lru(folio) is false, it implies that
> > !folio_test_swapbacked(folio) must be true.
>
> That is not true.
>
This is the definition of folio_is_file_lru() in
include/linux/mm_inline.h line 28:
static inline int folio_is_file_lru(struct folio *folio)
{
return !folio_test_swapbacked(folio);
}

> MADV_FREE pages are anonymous pages that are not swapbacked
> (and thus can be reclaimed without pageout if they are clean).
>
Thanks for the explanation! I'm new to memory management, so this is
really helpful for me to learn.

Best regards,
Jialin Wang