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

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Message-ID: <a9bbf82b-bed5-436b-814b-cd9fa3f976d0@kernel.org>
Date: Thu, 5 Feb 2026 13:36:16 +0100
From: "David Hildenbrand (Arm)" <david@...nel.org>
To: Ankur Arora <ankur.a.arora@...cle.com>,
 Andrew Morton <akpm@...ux-foundation.org>
Cc: 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 2/5/26 06:48, Ankur Arora wrote:
> 
> Andrew Morton <akpm@...ux-foundation.org> writes:
> 
>> On Wed, 4 Feb 2026 22:01:42 +0100 "David Hildenbrand (arm)" <david@...nel.org> wrote:
>>
>>>
>>> I'm late, maybe this is already upstream.
>>
>> It's in mm-unstable.  The second round of MM upstreaming is two weeks hence.
>>
>>>
>>> TBH, without the clamp that looks much more readable here.
>>
>> me too.
>>
>>>
>>> Is that cast really required?
>>
>> Seems not.  The types for nr_pages are a bit chaotic - u64->long->uint.
> 
> 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.

You could just make clear_contig_highpages() consume an unsigned long ...

-- 
Cheers,

David