linux-kernel - Re: [PATCH RFC 10/35] mm/hugetlb: cleanup hugetlb_folio_init_tail

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Message-ID: <7077e09f-6ce9-43ba-8f87-47a290680141@redhat.com>
Date: Fri, 22 Aug 2025 08:24:31 +0200
From: David Hildenbrand <david@...hat.com>
To: Mika Penttilä <mpenttil@...hat.com>,
 linux-kernel@...r.kernel.org
Cc: Alexander Potapenko <glider@...gle.com>,
 Andrew Morton <akpm@...ux-foundation.org>,
 Brendan Jackman <jackmanb@...gle.com>, Christoph Lameter <cl@...two.org>,
 Dennis Zhou <dennis@...nel.org>, Dmitry Vyukov <dvyukov@...gle.com>,
 dri-devel@...ts.freedesktop.org, intel-gfx@...ts.freedesktop.org,
 iommu@...ts.linux.dev, io-uring@...r.kernel.org,
 Jason Gunthorpe <jgg@...dia.com>, Jens Axboe <axboe@...nel.dk>,
 Johannes Weiner <hannes@...xchg.org>, John Hubbard <jhubbard@...dia.com>,
 kasan-dev@...glegroups.com, kvm@...r.kernel.org,
 "Liam R. Howlett" <Liam.Howlett@...cle.com>,
 Linus Torvalds <torvalds@...ux-foundation.org>, linux-arm-kernel@...s.com,
 linux-arm-kernel@...ts.infradead.org, linux-crypto@...r.kernel.org,
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 linux-scsi@...r.kernel.org, Lorenzo Stoakes <lorenzo.stoakes@...cle.com>,
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 Michal Hocko <mhocko@...e.com>, Mike Rapoport <rppt@...nel.org>,
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 Vlastimil Babka <vbabka@...e.cz>, wireguard@...ts.zx2c4.com, x86@...nel.org,
 Zi Yan <ziy@...dia.com>
Subject: Re: [PATCH RFC 10/35] mm/hugetlb: cleanup
 hugetlb_folio_init_tail_vmemmap()

On 22.08.25 06:09, Mika Penttilä wrote:
> 
> On 8/21/25 23:06, David Hildenbrand wrote:
> 
>> All pages were already initialized and set to PageReserved() with a
>> refcount of 1 by MM init code.
> 
> Just to be sure, how is this working with MEMBLOCK_RSRV_NOINIT, where MM is supposed not to
> initialize struct pages?

Excellent point, I did not know about that one.

Spotting that we don't do the same for the head page made me assume that 
it's just a misuse of __init_single_page().

But the nasty thing is that we use memblock_reserved_mark_noinit() to 
only mark the tail pages ...

Let me revert back to __init_single_page() and add a big fat comment why 
this is required.

Thanks!

-- 
Cheers

David / dhildenb