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

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Message-ID: <87ikygo1yb.fsf@oracle.com>
Date: Mon, 10 Jun 2024 15:41:32 -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

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
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