linux-kernel - Re: [PATCH v3 1/5] mm: Optimize mprotect() by batch-skipping PTEs

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Message-ID: <92cc1bfb-ab7a-4abc-afd0-49f8f2d12da0@arm.com>
Date: Wed, 4 Jun 2025 16:08:07 +0530
From: Dev Jain <dev.jain@....com>
To: David Hildenbrand <david@...hat.com>, akpm@...ux-foundation.org
Cc: ryan.roberts@....com, willy@...radead.org, linux-mm@...ck.org,
 linux-kernel@...r.kernel.org, catalin.marinas@....com, will@...nel.org,
 Liam.Howlett@...cle.com, lorenzo.stoakes@...cle.com, vbabka@...e.cz,
 jannh@...gle.com, anshuman.khandual@....com, peterx@...hat.com,
 joey.gouly@....com, ioworker0@...il.com, baohua@...nel.org,
 kevin.brodsky@....com, quic_zhenhuah@...cinc.com,
 christophe.leroy@...roup.eu, yangyicong@...ilicon.com,
 linux-arm-kernel@...ts.infradead.org, hughd@...gle.com,
 yang@...amperecomputing.com, ziy@...dia.com
Subject: Re: [PATCH v3 1/5] mm: Optimize mprotect() by batch-skipping PTEs


On 22/05/25 9:48 pm, David Hildenbrand wrote:
> On 22.05.25 09:47, Dev Jain wrote:
>>
>> On 22/05/25 12:43 pm, David Hildenbrand wrote:
>>>
>>>>> ... likely with a better function name,
>>>>
>>>>
>>>> I want to be able to reuse the folio from vm_normal_folio(), and we 
>>>> also
>>>> need
>>>>
>>>> nr_ptes to know how much to skip, so if there is no objection in 
>>>> passing
>>>> int *nr_ptes,
>>>>
>>>> or struct folio **foliop to this new function, then I'll carry on with
>>>> your suggestion :)
>>>
>>> Can you quickly prototype what you have in mind and paste it here?
>>> Will make it easier :)
>>
>>
>> if (prot_numa)
>>
>>       func(vma, addr, oldpte, &nr);
>
> I'd probably return "nr_ptes" and return the folio using a &folio 
> instead.
>
> That way, you can easily extend the function to return the folio in 
> the patch where you really need it (not this patch IIUR :) )

Just confirming, you mean to return nr_ptes and get the folio by passing 
&folio, and the function parameter will be struct folio **foliop?