linux-kernel - Re: [PATCH] mm: madvise: make MADV

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Message-ID: <42872c96-e9c5-4c3c-9095-3f12202dd803@lucifer.local>
Date: Wed, 14 May 2025 16:27:35 +0100
From: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
To: Ignacio Moreno Gonzalez <Ignacio.MorenoGonzalez@...a.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
        "Liam R. Howlett" <Liam.Howlett@...cle.com>,
        yang@...amperecomputing.com, willy@...radead.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm: madvise: make MADV_NOHUGEPAGE a no-op if !THP

Andrew - please hold fire given below. It seems we _can_ patch this after all :)

Missing context:

> Andrew - we should probably drop this patch for now given the report at [0].
>
> It seems s390 (to risk sounding hyperbolic - fairly ludicriously) declares
> PROT_NONE in an enum somewhere that blows this up.

On Wed, May 14, 2025 at 05:07:58PM +0200, Ignacio Moreno Gonzalez wrote:
> On 5/14/2025 3:52 PM, Lorenzo Stoakes wrote:

Igancio - you're deleting too much context here, you did it in the other email
too, it's really hard to follow what's going on. Please try to be careful about
what bits of an email you delete when quoting.

You're putting my comment here without the context of what I asked Andrew, so
now it's not clear what's going on.

>
> > I have pinged s390 people on there, but I don't think this is going to make this
> > cycle given we will probably need to coordinate with them to fix up this enum
> > name (which seems the best solution to me!...)
>
> They answered that it would be ok for them to do a quick fix over the mm tree:
>
> https://lore.kernel.org/linux-mm/6f8f3780-902b-49d4-a766-ea2e1a8f85ea@linux.ibm.com/

Yeah, we need to figure out who's going to do this patch though :)

Did you want to Iganacio?

I would suggest chasing up with them to see if they plan to do it or you ought
to do so.

I can also do it if you need it quick, but I don't want to deprive you of the
opportunity to patch that :)

They are happy for that to go in via the mm tree, so we should be able to do
this quick.

Thanks, Lorenzo

>
>
> >> +#include <uapi/asm/mman.h>
> >
> > Also this should be linux/mman.h I believe, sorry for not catching first time round...!
> >
>
> Including linux/mman.h leads to a compilation error:
>
> ../include/linux/huge_mm.h:601:23: error: ‘MADV_NOHUGEPAGE’
>
> Including uapi/linux/mman.h works, but I am not sure if that is correct.

OK this is because of a circular dependency (le sigh) as linux/mman.h itself
imports linux/mm.h (prior to including the headers that define this) that then
imports linux/huge_mm.h and welcome to hell.

Le sigh deux.

OK leave it as it is!

C headers are a pain.

>
>