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

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <b6fa0add-e739-499d-9fbf-32454b5e137a@linux.alibaba.com>
Date: Fri, 12 Sep 2025 16:31:38 +0800
From: Baolin Wang <baolin.wang@...ux.alibaba.com>
To: David Hildenbrand <david@...hat.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 2025/9/12 16:24, David Hildenbrand wrote:
> 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?

Please see the following check in pageout():

if (!shmem_mapping(mapping) && !folio_test_anon(folio))
	return PAGE_ACTIVATE;

>> 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.

Yes, but this also needs further cleanup, as kswapd also cannot reclaim 
filesystem dirty folios in pageout(). I plan to continue optimizing 
dirty file folios in isolate_lru_folios() to avoid some unnecessary scans.

>>> 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 :)
>