linux-kernel - Re: [PATCHv6 02/17] mm: Change the interface of prep_compound

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Message-ID: <8deb6010-3abd-48dd-8b77-40dbf2d48c65@kernel.org>
Date: Thu, 5 Feb 2026 12:58:37 +0100
From: "David Hildenbrand (arm)" <david@...nel.org>
To: Kiryl Shutsemau <kas@...nel.org>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
 Muchun Song <muchun.song@...ux.dev>, Matthew Wilcox <willy@...radead.org>,
 Usama Arif <usamaarif642@...il.com>, Frank van der Linden <fvdl@...gle.com>,
 Oscar Salvador <osalvador@...e.de>, Mike Rapoport <rppt@...nel.org>,
 Vlastimil Babka <vbabka@...e.cz>,
 Lorenzo Stoakes <lorenzo.stoakes@...cle.com>, Zi Yan <ziy@...dia.com>,
 Baoquan He <bhe@...hat.com>, Michal Hocko <mhocko@...e.com>,
 Johannes Weiner <hannes@...xchg.org>, Jonathan Corbet <corbet@....net>,
 Huacai Chen <chenhuacai@...nel.org>, WANG Xuerui <kernel@...0n.name>,
 Palmer Dabbelt <palmer@...belt.com>, Paul Walmsley
 <paul.walmsley@...ive.com>, Albert Ou <aou@...s.berkeley.edu>,
 Alexandre Ghiti <alex@...ti.fr>, kernel-team@...a.com, linux-mm@...ck.org,
 linux-kernel@...r.kernel.org, linux-doc@...r.kernel.org,
 loongarch@...ts.linux.dev, linux-riscv@...ts.infradead.org
Subject: Re: [PATCHv6 02/17] mm: Change the interface of prep_compound_tail()

On 2/5/26 12:35, Kiryl Shutsemau wrote:
> On Wed, Feb 04, 2026 at 05:14:12PM +0100, David Hildenbrand (arm) wrote:
>> On 2/2/26 16:56, Kiryl Shutsemau wrote:
>>> Instead of passing down the head page and tail page index, pass the tail
>>> and head pages directly, as well as the order of the compound page.
>>>
>>> This is a preparation for changing how the head position is encoded in
>>> the tail page.
>>>
>>> Signed-off-by: Kiryl Shutsemau <kas@...nel.org>
>>> Reviewed-by: Muchun Song <muchun.song@...ux.dev>
>>> Reviewed-by: Zi Yan <ziy@...dia.com>
>>> ---
>>>    include/linux/page-flags.h |  4 +++-
>>>    mm/hugetlb.c               |  8 +++++---
>>>    mm/internal.h              | 12 ++++++------
>>>    mm/mm_init.c               |  2 +-
>>>    mm/page_alloc.c            |  2 +-
>>>    5 files changed, 16 insertions(+), 12 deletions(-)
>>>
>>> diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h
>>> index f7a0e4af0c73..8a3694369e15 100644
>>> --- a/include/linux/page-flags.h
>>> +++ b/include/linux/page-flags.h
>>> @@ -865,7 +865,9 @@ static inline bool folio_test_large(const struct folio *folio)
>>>    	return folio_test_head(folio);
>>>    }
>>> -static __always_inline void set_compound_head(struct page *page, struct page *head)
>>> +static __always_inline void set_compound_head(struct page *page,
>>> +					      const struct page *head,
>>> +					      unsigned int order)
>>
>> Two tab indents please on second+ parameter list whenever you touch code.
> 
> Do we have this coding style preference written down somewhere?

Good question. I assume not. But it's what we do in MM :)

> 
> -tip tree wants the opposite. Documentation/process/maintainer-tip.rst:
> 
> 	When splitting function declarations or function calls, then please align
> 	the first argument in the second line with the first argument in the first
> 	line::
> 
> I want the editor to do The Right Thing™ without my brain involvement.
> Having different coding styles in different corners of the kernel makes
> it hard.

Yeah, but unavoidable. :)

-- 
Cheers,

David