linux-kernel - Re: [PATCH v4] mm: convert page type macros to enum

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Date: Mon, 17 Jun 2024 13:34:21 -0700
From: Stephen Brennan <stephen.s.brennan@...cle.com>
To: Andrew Morton <akpm@...ux-foundation.org>
Cc: linux-mm@...ck.org, Vlastimil Babka <vbabka@...e.cz>,
        "Vishal Moola
 (Oracle)" <vishal.moola@...il.com>,
        Omar Sandoval <osandov@...ndov.com>,
        David Hildenbrand <david@...hat.com>,
        "Matthew Wilcox (Oracle)"
 <willy@...radead.org>,
        Hao Ge <gehao@...inos.cn>, linux-debuggers@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4] mm: convert page type macros to enum

Stephen Brennan <stephen.s.brennan@...cle.com> writes:
> Andrew Morton <akpm@...ux-foundation.org> writes:
>
>> On Fri,  7 Jun 2024 13:29:53 -0700 Stephen Brennan <stephen.s.brennan@...cle.com> wrote:
>>
>>> Changing PG_slab from a page flag to a page type in commit 46df8e73a4a3
>>> ("mm: free up PG_slab") in has the unintended consequence of removing
>>> the PG_slab constant from kernel debuginfo. The commit does add the
>>> value to the vmcoreinfo note, which allows debuggers to find the value
>>> without hardcoding it. However it's most flexible to continue
>>> representing the constant with an enum. To that end, convert the page
>>> type fields into an enum. Debuggers will now be able to detect that
>>> PG_slab's type has changed from enum pageflags to enum pagetype.
>>> 
>>> Fixes: 46df8e73a4a3 ("mm: free up PG_slab")
>>
>> Should we backport this into 6.9.x?
>
> Hi Andrew,
>
> Looks like commit 46df8e73a4a3 ("mm: free up PG_slab") is introduced in
> the v6.10-rc's, and not backported to 6.9. So PG_slab is still part of

Hi Andrew,

I saw that you've merged this into mm-unstable, thank you!

Since 46df8e73a4a3 ("mm: free up PG_slab") is part of the current 6.10
RC, it would be great if this patch could be part of the 6.10 release so
we don't release a kernel missing the PG_slab info.

Can you confirm if mm-unstable will get merged in this release cycle? Or
else, would it be possible to include it in a branch that will?

Thanks,
Stephen

> enum pageflags in 6.9. From the perspective of the issue which motivated
> this patch, there's no reason to backport.
>
> Backporting could make the other enum pagetype constants available in
> 6.9, but I'm not sure there are any users who would care for that. I'd
> say there's no need.
>
> Thanks,
> Stephen