linux-kernel - Re: [RFC v2 1/3] filemap: set max order to be min order if THP is disabled

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Message-ID: <d395cf62-2066-4965-87e6-823a7bbde775@suse.de>
Date: Tue, 9 Dec 2025 08:45:46 +0100
From: Hannes Reinecke <hare@...e.de>
To: Pankaj Raghav <p.raghav@...sung.com>,
 Suren Baghdasaryan <surenb@...gle.com>, Mike Rapoport <rppt@...nel.org>,
 David Hildenbrand <david@...hat.com>, Ryan Roberts <ryan.roberts@....com>,
 Michal Hocko <mhocko@...e.com>, Lance Yang <lance.yang@...ux.dev>,
 Lorenzo Stoakes <lorenzo.stoakes@...cle.com>,
 Baolin Wang <baolin.wang@...ux.alibaba.com>, Dev Jain <dev.jain@....com>,
 Barry Song <baohua@...nel.org>, Andrew Morton <akpm@...ux-foundation.org>,
 Nico Pache <npache@...hat.com>, Zi Yan <ziy@...dia.com>,
 Vlastimil Babka <vbabka@...e.cz>, "Liam R . Howlett"
 <Liam.Howlett@...cle.com>, Jens Axboe <axboe@...nel.dk>
Cc: linux-kernel@...r.kernel.org, linux-mm@...ck.org,
 linux-block@...r.kernel.org, linux-fsdevel@...r.kernel.org,
 mcgrof@...nel.org, gost.dev@...sung.com, kernel@...kajraghav.com,
 tytso@....edu
Subject: Re: [RFC v2 1/3] filemap: set max order to be min order if THP is
 disabled

On 12/6/25 04:08, Pankaj Raghav wrote:
> Large folios in the page cache depend on the splitting infrastructure from
> THP. To remove the dependency between large folios and
> CONFIG_TRANSPARENT_HUGEPAGE, set the min order == max order if THP is
> disabled. This will make sure the splitting code will not be required
> when THP is disabled, therefore, removing the dependency between large
> folios and THP.
> 
The description is actually misleading.
It's not that you remove the dependency from THP for large folios
_in general_ (the CONFIG_THP is retained in this patch).
Rather you remove the dependency for large folios _for the block layer_.
And that should be make explicit in the description, otherwise the
description and the patch doesn't match.

Cheers,

Hannes
-- 
Dr. Hannes Reinecke                  Kernel Storage Architect
hare@...e.de                                +49 911 74053 688
SUSE Software Solutions GmbH, Frankenstr. 146, 90461 Nürnberg
HRB 36809 (AG Nürnberg), GF: I. Totev, A. McDonald, W. Knoblich