linux-kernel - Re: [PATCH V3 2/5] mm/khugepaged: count small VMAs towards scan limit

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <836669ac-473f-4c30-a368-c05bfa86c306@amd.com>
Date: Fri, 23 Jan 2026 16:12:07 +0530
From: "Garg, Shivank" <shivankg@....com>
To: Andrew Morton <akpm@...ux-foundation.org>
Cc: Zi Yan <ziy@...dia.com>, Baolin Wang <baolin.wang@...ux.alibaba.com>,
 "Liam R . Howlett" <Liam.Howlett@...cle.com>, Nico Pache
 <npache@...hat.com>, David Hildenbrand <david@...nel.org>,
 Ryan Roberts <ryan.roberts@....com>, Barry Song <baohua@...nel.org>,
 linux-mm@...ck.org, linux-kernel@...r.kernel.org,
 Wei Yang <richard.weiyang@...il.com>,
 Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
Subject: Re: [PATCH V3 2/5] mm/khugepaged: count small VMAs towards scan limit

On 1/22/2026 5:56 PM, Garg, Shivank wrote:
> 
> 
> On 1/22/2026 2:14 PM, Lance Yang wrote:
>>
>>
>> On 2026/1/22 15:32, Dev Jain wrote:
>>>
>>> On 19/01/26 12:52 am, Shivank Garg wrote:
>>>> The khugepaged_scan_mm_slot() uses a 'progress' counter to limit the
>>>> amount of work performed and consists of three components:
>>>> 1. Transitioning to a new mm (+1).
>>>> 2. Skipping an unsuitable VMA (+1).
>>>> 3. Scanning a PMD-sized range (+HPAGE_PMD_NR).
>>>>
>>>> Consider a 1MB VMA sitting between two 2MB alignment boundaries:
>>>>
>>>>       vma1       vma2   vma3
>>>>      +----------+------+----------+
>>>>      |2M        |1M    |2M        |
>>>>      +----------+------+----------+
>>>>                 ^      ^
>>>>                 start  end
>>>>                 ^
>>>>            hstart,hend
>>>
>>> Won't such a VMA be skipped by thp_vma_allowable_order()? That internally
>>> checks, apart from eligibility by sysfs, that the extent of the VMA can
>>> map a hugepage.
>>
>> Ah, you're right!
>>
>> I was worrying about a case that doesn't actually happen.
>>
> You're right, thp_vma_allowable_order() is taking care of this, making 
> hend <= hstart check redundant.
> 
> Thank you for catching this.
> 
> I'll drop this change and send revision keeping only the unsigned int type 
> change for 'progress'.
> 

Hi Andrew,

Please drop this patch.

As Dev and Lance noted that the hend <= hstart handling check is redundant.

The 'progress' variable to unsigned int is not critical either.

Other patches from series remain unchanged.
Sorry for the noise, and thanks.

Regards,
Shivank