linux-kernel - Re: [PATCH mm-new v3 1/1] mm/khugepaged: abort collapse scan on non-swap entries

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: <7d3ac12c-c3a5-4913-93cf-98c887f67397@lucifer.local>
Date: Tue, 14 Oct 2025 17:10:39 +0100
From: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
To: David Hildenbrand <david@...hat.com>
Cc: Lance Yang <lance.yang@...ux.dev>, akpm@...ux-foundation.org,
        Liam.Howlett@...cle.com, baohua@...nel.org,
        baolin.wang@...ux.alibaba.com, dev.jain@....com, hughd@...gle.com,
        ioworker0@...il.com, kirill@...temov.name,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org, mpenttil@...hat.com,
        npache@...hat.com, ryan.roberts@....com, ziy@...dia.com,
        richard.weiyang@...il.com
Subject: Re: [PATCH mm-new v3 1/1] mm/khugepaged: abort collapse scan on
 non-swap entries

On Tue, Oct 14, 2025 at 05:33:18PM +0200, David Hildenbrand wrote:
> For the sake of progress, I assume the compiler will optimize out the
> additional pte_none() stuff.
>
> I absolutely, absolutely hate is_swap_pte(). To me, it makes the code more
> confusing that talking about something that is !present but also !none:
> there is something that is not an ordinary page table mapping.

Yeah it's nasty for sure.

I hate non-swap-entry swap entries with a passion.

We clearly need to rework this... :)

Naming is hard however...

>
> The underlying problem is how we hacked in non-swap into swap (and that's
> exactly where it gets confusing). Well, which this series is all about.

Yup

>
> So, I don't care in the end here.

I do still feel a single guard condition works better than having to know
implementaiton details so would still prefer this change to be made.

>
> --
> Cheers
>
> David / dhildenb
>

Cheers, Lorenzo