linux-kernel - Re: [PATCH v2 1/5] mm: move huge_zero_page declaration from huge

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Message-ID: <hi7i4k7gbbd27mtjyucwxjgwhjq7z4wtzm2nd6fqfnd5m7yo52@k7vwf576a44x>
Date: Wed, 16 Jul 2025 09:47:47 +0200
From: "Pankaj Raghav (Samsung)" <kernel@...kajraghav.com>
To: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
Cc: Suren Baghdasaryan <surenb@...gle.com>, 
	Ryan Roberts <ryan.roberts@....com>, Baolin Wang <baolin.wang@...ux.alibaba.com>, 
	Borislav Petkov <bp@...en8.de>, Ingo Molnar <mingo@...hat.com>, 
	"H . Peter Anvin" <hpa@...or.com>, Vlastimil Babka <vbabka@...e.cz>, Zi Yan <ziy@...dia.com>, 
	Mike Rapoport <rppt@...nel.org>, Dave Hansen <dave.hansen@...ux.intel.com>, 
	Michal Hocko <mhocko@...e.com>, David Hildenbrand <david@...hat.com>, 
	Andrew Morton <akpm@...ux-foundation.org>, Thomas Gleixner <tglx@...utronix.de>, 
	Nico Pache <npache@...hat.com>, Dev Jain <dev.jain@....com>, 
	"Liam R . Howlett" <Liam.Howlett@...cle.com>, Jens Axboe <axboe@...nel.dk>, linux-kernel@...r.kernel.org, 
	willy@...radead.org, linux-mm@...ck.org, x86@...nel.org, linux-block@...r.kernel.org, 
	linux-fsdevel@...r.kernel.org, "Darrick J . Wong" <djwong@...nel.org>, mcgrof@...nel.org, 
	gost.dev@...sung.com, hch@....de, Pankaj Raghav <p.raghav@...sung.com>
Subject: Re: [PATCH v2 1/5] mm: move huge_zero_page declaration from
 huge_mm.h to mm.h

On Tue, Jul 15, 2025 at 03:08:40PM +0100, Lorenzo Stoakes wrote:
> On Mon, Jul 07, 2025 at 04:23:15PM +0200, Pankaj Raghav (Samsung) wrote:
> > From: Pankaj Raghav <p.raghav@...sung.com>
> >
> > Move the declaration associated with huge_zero_page from huge_mm.h to
> > mm.h. This patch is in preparation for adding static PMD zero page as we
> > will be reusing some of the huge_zero_page infrastructure.
> 
> Hmm this is really iffy.
> 
> The whole purpose of huge_mm.h is to handle huge page stuff, and now you're
> moving it to a general header... not a fan of this - now we have _some_
> huge stuff in mm.h and some stuff here.
> 
> Yes this might be something we screwed up already, but that's not a recent
> to perpetuate mistakes.
> 
> Surely you don't _need_ to do this and this is a question of fixing up
> header includes right?
> 
> Or is them some horrible cyclical header issue here?
> 
> Also your commit message doesn't give any reason as to why you _need_ to do
> this also. For something like this where you're doing something that at
> face value seems to contradict the purpose of these headers, you need to
> explain why.
> 

In one of the earlier versions, David asked me to experiment by moving some of these
declarations to mm.h and see how it looks. Mainly because, as you
guessed it later, we can use it without THP being enabled.

But I see that you strongly feel against moving this to mm.h (and I see
why).

I can move it back to huge_mm.h.

Thanks

--
Pankaj