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Subject: Re: [PATCH v4 6/6] mm/mm_init: add zone mismatch warning during page
 init
From: Muchun Song <muchun.song@linux.dev>
In-Reply-To: <asoMN5F-3qvaW5w0@kernel.org>
Date: Sat, 10 Oct 2026 18:33:59 +0800
Cc: Muchun Song <songmuchun@bytedance.com>,
 Madhavan Srinivasan <maddy@linux.ibm.com>,
 Andrew Morton <akpm@linux-foundation.org>,
 David Hildenbrand <david@kernel.org>,
 Michael Ellerman <mpe@ellerman.id.au>,
 Nicholas Piggin <npiggin@gmail.com>,
 Christophe Leroy <chleroy@kernel.org>,
 Ritesh Harjani <ritesh.list@gmail.com>,
 Shrikanth Hegde <sshegde@linux.ibm.com>,
 Lorenzo Stoakes <ljs@kernel.org>,
 "Liam R . Howlett" <liam@infradead.org>,
 Vlastimil Babka <vbabka@kernel.org>,
 Suren Baghdasaryan <surenb@google.com>,
 Michal Hocko <mhocko@suse.com>,
 Qi Zheng <qi.zheng@linux.dev>,
 Lance Yang <lance.yang@linux.dev>,
 linuxppc-dev@lists.ozlabs.org,
 linux-kernel@vger.kernel.org,
 linux-mm@kvack.org
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References: <20261010075755.83339-1-songmuchun@bytedance.com>
 <20261010075755.83339-7-songmuchun@bytedance.com>
 <434B0573-BF18-4413-9BDF-C5873CC13206@linux.dev>
 <asoMN5F-3qvaW5w0@kernel.org>
To: Mike Rapoport <rppt@kernel.org>
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> On Oct 10, 2026, at 17:58, Mike Rapoport <rppt@kernel.org> wrote:
>=20
> On Sat, Oct 10, 2026 at 05:32:59PM +0800, Muchun Song wrote:
>>=20
>>=20
>>> On Oct 10, 2026, at 15:57, Muchun Song <songmuchun@bytedance.com> =
wrote:
>>>=20
>>> For vmemmap-optimized sections, tail struct pages may be backed by
>>> shared vmemmap pages. Those shared pages must carry the same page =
zone
>>> ID as the struct pages initialized for the section.
>>>=20
>>> Warn in __init_single_page() if the shared tail page has a different
>>> page_zone_id(), which would indicate inconsistent initialization.
>>=20
>> Please ignore Sashiko's report [1], both are false positive. It =
didn't
>> realize that shared vmemmap pages are initialized early before =
__init_single_page().
>=20
> I didn't realize it too when I read this first :)
>=20
> How about a short comment above vmemmap_optimization_verify_zone()?

Good point. A short comment there would be helpful.

Thanks,
Muchun

>=20
>> [1] =
https://sashiko.dev/#/patchset/20261010075755.83339-1-songmuchun%40bytedan=
ce.com?part=3D6
>>=20
>> Thanks.
>=20
> --=20
> Sincerely yours,
> Mike.