From: Matthew Wilcox <willy@infradead.org>
To: Kiryl Shutsemau <kas@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Muchun Song <muchun.song@linux.dev>,
David Hildenbrand <david@redhat.com>,
Usama Arif <usamaarif642@gmail.com>,
Frank van der Linden <fvdl@google.com>,
Oscar Salvador <osalvador@suse.de>,
Mike Rapoport <rppt@kernel.org>, Vlastimil Babka <vbabka@suse.cz>,
Lorenzo Stoakes <lorenzo.stoakes@oracle.com>,
Zi Yan <ziy@nvidia.com>, Baoquan He <bhe@redhat.com>,
Michal Hocko <mhocko@suse.com>,
Johannes Weiner <hannes@cmpxchg.org>,
Jonathan Corbet <corbet@lwn.net>,
Huacai Chen <chenhuacai@kernel.org>,
WANG Xuerui <kernel@xen0n.name>,
Palmer Dabbelt <palmer@dabbelt.com>,
Paul Walmsley <paul.walmsley@sifive.com>,
Albert Ou <aou@eecs.berkeley.edu>,
Alexandre Ghiti <alex@ghiti.fr>,
kernel-team@meta.com, linux-mm@kvack.org,
linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org,
loongarch@lists.linux.dev, linux-riscv@lists.infradead.org
Subject: Re: [PATCHv6 08/17] mm: Make page_zonenum() use head page
Date: Sun, 15 Feb 2026 23:13:51 +0000 [thread overview]
Message-ID: <aZJTLwV2SaaKu1k_@casper.infradead.org> (raw)
In-Reply-To: <20260202155634.650837-9-kas@kernel.org>
On Mon, Feb 02, 2026 at 03:56:24PM +0000, Kiryl Shutsemau wrote:
> With the upcoming changes to HVO, a single page of tail struct pages
> will be shared across all huge pages of the same order on a node. Since
> huge pages on the same node may belong to different zones, the zone
> information stored in shared tail page flags would be incorrect.
>
> Always fetch zone information from the head page, which has unique and
> correct zone flags for each compound page.
You're right that different pages in the same folio can have different
zone number. But does it matter ... or to put it another way, why is
returning the zone number of the head page the correct way to resolve
this?
Arguably, the caller is asking for the zone number of _this page_, and
does not care about the zone number of the head page. It would be good
to have a short discussion of this in the commit message (but probably
not worth putting this in a comment).
next prev parent reply other threads:[~2026-02-15 23:21 UTC|newest]
Thread overview: 67+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-02-02 15:56 [PATCHv6 00/17] mm: Eliminate fake head pages from vmemmap optimization Kiryl Shutsemau
2026-02-02 15:56 ` [PATCHv6 01/17] mm: Move MAX_FOLIO_ORDER definition to mmzone.h Kiryl Shutsemau
2026-02-07 20:20 ` Usama Arif
2026-02-10 15:01 ` Vlastimil Babka
2026-02-02 15:56 ` [PATCHv6 02/17] mm: Change the interface of prep_compound_tail() Kiryl Shutsemau
2026-02-04 16:14 ` David Hildenbrand (arm)
2026-02-05 11:35 ` Kiryl Shutsemau
2026-02-05 11:58 ` David Hildenbrand (arm)
2026-02-10 15:06 ` Vlastimil Babka
2026-02-02 15:56 ` [PATCHv6 03/17] mm: Rename the 'compound_head' field in the 'struct page' to 'compound_info' Kiryl Shutsemau
2026-02-04 16:14 ` David Hildenbrand (arm)
2026-02-10 15:09 ` Vlastimil Babka
2026-02-02 15:56 ` [PATCHv6 04/17] mm: Move set/clear_compound_head() next to compound_head() Kiryl Shutsemau
2026-02-04 16:35 ` David Hildenbrand (arm)
2026-02-10 15:10 ` Vlastimil Babka
2026-02-02 15:56 ` [PATCHv6 05/17] riscv/mm: Align vmemmap to maximal folio size Kiryl Shutsemau
2026-02-04 16:50 ` David Hildenbrand (arm)
2026-02-05 13:50 ` Kiryl Shutsemau
2026-02-05 13:54 ` David Hildenbrand (Arm)
2026-02-02 15:56 ` [PATCHv6 06/17] LoongArch/mm: " Kiryl Shutsemau
2026-02-04 16:56 ` David Hildenbrand (arm)
2026-02-05 12:56 ` David Hildenbrand (Arm)
2026-02-05 13:43 ` Kiryl Shutsemau
2026-02-05 13:52 ` David Hildenbrand (Arm)
2026-02-05 13:52 ` Kiryl Shutsemau
2026-02-05 13:57 ` David Hildenbrand (Arm)
2026-02-02 15:56 ` [PATCHv6 07/17] mm: Rework compound_head() for power-of-2 sizeof(struct page) Kiryl Shutsemau
2026-02-05 14:09 ` David Hildenbrand (Arm)
2026-02-07 20:19 ` Usama Arif
2026-02-10 15:40 ` Vlastimil Babka
2026-02-02 15:56 ` [PATCHv6 08/17] mm: Make page_zonenum() use head page Kiryl Shutsemau
2026-02-04 3:40 ` Muchun Song
2026-02-05 13:10 ` David Hildenbrand (Arm)
2026-02-09 11:52 ` Kiryl Shutsemau
2026-02-10 15:57 ` Vlastimil Babka
2026-02-16 11:30 ` Kiryl Shutsemau
2026-02-15 23:13 ` Matthew Wilcox [this message]
2026-02-16 9:06 ` David Hildenbrand (Arm)
2026-02-16 11:20 ` Vlastimil Babka
2026-02-02 15:56 ` [PATCHv6 09/17] mm/sparse: Check memmap alignment for compound_info_has_mask() Kiryl Shutsemau
2026-02-03 3:35 ` Muchun Song
2026-02-05 13:31 ` David Hildenbrand (Arm)
2026-02-05 13:58 ` David Hildenbrand (Arm)
2026-02-02 15:56 ` [PATCHv6 10/17] mm/hugetlb: Refactor code around vmemmap_walk Kiryl Shutsemau
2026-02-02 15:56 ` [PATCHv6 11/17] mm/hugetlb: Remove fake head pages Kiryl Shutsemau
2026-02-03 9:50 ` Muchun Song
2026-02-06 9:14 ` David Hildenbrand (Arm)
2026-02-06 9:36 ` David Hildenbrand (Arm)
2026-02-07 20:16 ` Usama Arif
2026-02-07 21:25 ` David Hildenbrand (Arm)
2026-02-07 22:50 ` Usama Arif
2026-02-02 15:56 ` [PATCHv6 12/17] mm: Drop fake head checks Kiryl Shutsemau
2026-02-06 9:41 ` David Hildenbrand (Arm)
2026-02-10 16:18 ` Vlastimil Babka
2026-02-02 15:56 ` [PATCHv6 13/17] hugetlb: Remove VMEMMAP_SYNCHRONIZE_RCU Kiryl Shutsemau
2026-02-06 9:42 ` David Hildenbrand (Arm)
2026-02-02 15:56 ` [PATCHv6 14/17] mm/hugetlb: Remove hugetlb_optimize_vmemmap_key static key Kiryl Shutsemau
2026-02-06 9:42 ` David Hildenbrand (Arm)
2026-02-02 15:56 ` [PATCHv6 15/17] mm: Remove the branch from compound_head() Kiryl Shutsemau
2026-02-06 10:23 ` David Hildenbrand (Arm)
2026-02-10 16:42 ` Vlastimil Babka
2026-02-02 15:56 ` [PATCHv6 16/17] hugetlb: Update vmemmap_dedup.rst Kiryl Shutsemau
2026-02-06 10:35 ` David Hildenbrand (Arm)
2026-02-02 15:56 ` [PATCHv6 17/17] mm/slab: Use compound_head() in page_slab() Kiryl Shutsemau
2026-02-04 3:39 ` Muchun Song
2026-02-06 10:42 ` David Hildenbrand (Arm)
2026-02-10 16:45 ` Vlastimil Babka
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