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

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Message-ID: <94cfb423-1dc5-43e1-bd1f-75b8d43fdc1a@redhat.com>
Date: Fri, 12 Sep 2025 10:24:47 +0200
From: David Hildenbrand <david@...hat.com>
To: Baolin Wang <baolin.wang@...ux.alibaba.com>, akpm@...ux-foundation.org,
 hannes@...xchg.org
Cc: mhocko@...nel.org, zhengqi.arch@...edance.com, shakeel.butt@...ux.dev,
 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 12.09.25 10:24, David Hildenbrand wrote:
> On 12.09.25 05:45, 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.
> 
> Can you point me at the code where that is fenced off?
> 
> I can spot a folio_is_file_lru() check before we call it, but the
> description tells me that there are indeed ways we could still pass that
> check for file-lru folios if we are kswapd.
> 
>> 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.
> 
> If that's indeed the case, do we still need the folio_test_private()
> check in is_page_cache_freeable()?

Ah, that's patch #2 :)

-- 
Cheers

David / dhildenb