linux-kernel - Re: [PATCH v2] mm: folio_zero_user: open code range computation in folio_zero

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Message-ID: <b1a8fa64-b690-4125-815f-46f61b65bc16@kernel.org>
Date: Fri, 6 Feb 2026 09:57:31 +0100
From: "David Hildenbrand (Arm)" <david@...nel.org>
To: Ankur Arora <ankur.a.arora@...cle.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>, linux-kernel@...r.kernel.org,
 linux-mm@...ck.org, x86@...nel.org, bp@...en8.de,
 dave.hansen@...ux.intel.com, hpa@...or.com, mingo@...hat.com,
 mjguzik@...il.com, luto@...nel.org, peterz@...radead.org,
 tglx@...utronix.de, willy@...radead.org, raghavendra.kt@....com,
 chleroy@...nel.org, ioworker0@...il.com, lizhe.67@...edance.com,
 boris.ostrovsky@...cle.com, konrad.wilk@...cle.com,
 kernel test robot <lkp@...el.com>
Subject: Re: [PATCH v2] mm: folio_zero_user: open code range computation in
 folio_zero_user()

On 2/6/26 06:42, Ankur Arora wrote:
> 
> David Hildenbrand (Arm) <david@...nel.org> writes:
> 
>> On 2/5/26 06:48, Ankur Arora wrote:
>>> Andrew Morton <akpm@...ux-foundation.org> writes:
>>>
>>> Yes agreed.
>>> The first u64 is because currently struct range only supports that.
>>> Then the cast to signed long is because the range can be negative
>>> and the clear_contig_highpages() is only done if nr_pages > 0.
>>
>> That makes sense to me.
>>
>>> And, the third one is almost certainly unnecessary for any realistic
>>> hugepage size but since nr_pages is being truncating, I wanted that
>>> to be explicit.
>>
>> But the non-silent truncation is no better? IOW, it doesn't matter.
> 
> I never seem to get them but I thought we had some kconfig option that
> makes gcc give a warning to that effect.

I think we do it all the time :)

> 
> I can update this patch to just implicitly truncate.
> 

Yeah, I think the implicit once can just be dropped.

>> You could just make clear_contig_highpages() consume an unsigned long ...
> 
> Unfortunately that'll be an even bigger mess. The clear_contig_highpages()
> version in mm-stable uses the unsigned intness of nr_pages all over:

Right.

In any case, thanks and feel free to add

Acked-by: David Hildenbrand (Arm) <david@...nel.org>

-- 
Cheers,

David