linux-kernel - Re: Linux 6.18-rc6

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Message-ID: <CAHk-=wg5dtEx63dm4fy-DkrX4Hw0htLyzPPbOhbYYxt4ESReDw@mail.gmail.com>
Date: Mon, 17 Nov 2025 09:28:33 -0800
From: Linus Torvalds <torvalds@...ux-foundation.org>
To: "David Hildenbrand (Red Hat)" <david@...nel.org>
Cc: David Wang <00107082@....com>, catalin.marinas@....com, lance.yang@...ux.dev, 
	b-padhi@...com, akpm@...ux-foundation.org, linux-kernel@...r.kernel.org, 
	Jan Polensky <japo@...ux.ibm.com>
Subject: Re: Linux 6.18-rc6

On Mon, 17 Nov 2025 at 06:08, David Hildenbrand (Red Hat)
<david@...nel.org> wrote:
>
> To not lose too much time, I just pushed the following patch to
>
> https://github.com/davidhildenbrand/linux.git zerotags

Hmm. Why isn't the fix for this simply this (intentionally
whitespace-damaged - don't apply mindlessly) one-liner:

  --- a/include/linux/highmem.h
  +++ b/include/linux/highmem.h
  @@ -253,5 +253,6 @@ static inline void
clear_highpage_kasan_tagged(struct page *page)

   static inline void tag_clear_highpage(struct page *page)
   {
  +     clear_highpage(page);
   }

because even when the *real* tag_clear_highpage() triggers, it falls down to

        if (!system_supports_mte()) {
                clear_highpage(page);
                return;
        }

so basically I think the fundamental bug here is that our fallback
tag_clear_highpage() was just buggy and didn't do what it was supposed
to do.

That one-liner would seem to be a lot simpler and more robust than
making this configuration-dependent. Just make the fallback do the
right thing - blammo, problem solved.

Am I missing something?

            Linus