From: Matthew Wilcox <willy@infradead.org>
To: "David Hildenbrand (Arm)" <david@kernel.org>
Cc: Kiryl Shutsemau <kas@kernel.org>,
Andrew Morton <akpm@linux-foundation.org>,
Muchun Song <muchun.song@linux.dev>,
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: Mon, 23 Feb 2026 18:18:03 +0000 [thread overview]
Message-ID: <aZyZ2-7Xr-zUnInC@casper.infradead.org> (raw)
In-Reply-To: <ec4a9a1e-8c08-4879-a787-3b9e0bc38160@kernel.org>
On Mon, Feb 16, 2026 at 10:06:57AM +0100, David Hildenbrand (Arm) wrote:
> On 2/16/26 00:13, Matthew Wilcox wrote:
> > 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?
>
> How can a folio cross zones?
I thought 1GB pages in hugetlb could cross zones? Maybe that used to be
true and isn't any more, or maybe it was never true and I was just
confused.
next prev parent reply other threads:[~2026-02-23 18:18 UTC|newest]
Thread overview: 71+ 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
2026-02-23 14:52 ` Kiryl Shutsemau
2026-02-15 23:13 ` Matthew Wilcox
2026-02-16 9:06 ` David Hildenbrand (Arm)
2026-02-16 11:20 ` Vlastimil Babka
2026-02-23 18:18 ` Matthew Wilcox [this message]
2026-02-23 19:32 ` David Hildenbrand (Arm)
2026-02-23 20:46 ` Frank van der Linden
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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