From: "David Hildenbrand (Arm)" <david@kernel.org>
To: Peter Zijlstra <peterz@infradead.org>, Kiryl Shutsemau <kas@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Muchun Song <muchun.song@linux.dev>,
Matthew Wilcox <willy@infradead.org>,
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,
Dave Hansen <dave.hansen@linux.intel.com>,
Andy Lutomirski <luto@kernel.org>
Subject: Re: [PATCHv7 13/18] mm: Drop fake head checks
Date: Tue, 27 Oct 2026 13:58:01 +0100 [thread overview]
Message-ID: <1de9a768-5cb3-435b-8a36-d8b590c8a33e@kernel.org> (raw)
In-Reply-To: <20261027124716.GC2668804@noisy.programming.kicks-ass.net>
On 10/27/26 13:47, Peter Zijlstra wrote:
> On Tue, Oct 27, 2026 at 12:31:09PM +0000, Kiryl Shutsemau wrote:
>> On Tue, Oct 27, 2026 at 01:05:58PM +0100, David Hildenbrand (Arm) wrote:
>>>
>>> Right. Without HVO we would just corrupt pages in the single folio (which is
>>> also not nice).
>>>
>>> I'm also questioning whether we need this RO protection all the time active.
>>
>> What do you have in mind? RO only under a debug option, or switching the
>> tail page to RO some time after the remap?
>>
>> If it is the delay, a grace period alone does not close the race. We
>> would need rcu_read_lock() back around the get, and then it is the old
>> scheme with the wait taken off the allocation path.
>
> So it used to be; back when Nick introduced try_get_page, that it was
> only allowed with IRQs disabled.
>
> And looking at gup.c now, I see gup_fast_pgd_range() still has
> local_irq_save/restore around it.
>
> So what do you need that rcu crud for?
Pagecache lookup (and other speculative page table walkers) call it as well.
Some with IRQ disabled, some with RCU, others with no protection.
--
Cheers,
David
next prev parent reply other threads:[~2026-10-27 12:58 UTC|newest]
Thread overview: 53+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-02-27 19:42 [PATCHv7 RESEND 00/17] mm: Eliminate fake head pages from vmemmap optimization Kiryl Shutsemau (Meta)
2026-02-27 19:42 ` [PATCHv7 01/18] mm: Move MAX_FOLIO_ORDER definition to mmzone.h Kiryl Shutsemau (Meta)
2026-02-27 19:42 ` [PATCHv7 02/18] mm: Change the interface of prep_compound_tail() Kiryl Shutsemau (Meta)
2026-02-27 19:42 ` [PATCHv7 03/18] mm: Rename the 'compound_head' field in the 'struct page' to 'compound_info' Kiryl Shutsemau (Meta)
2026-02-27 19:42 ` [PATCHv7 04/18] mm: Move set/clear_compound_head() next to compound_head() Kiryl Shutsemau (Meta)
2026-02-27 19:42 ` [PATCHv7 05/18] riscv/mm: Align vmemmap to maximal folio size Kiryl Shutsemau (Meta)
2026-03-16 16:30 ` David Hildenbrand (Arm)
2026-02-27 19:42 ` [PATCHv7 06/18] LoongArch/mm: " Kiryl Shutsemau (Meta)
2026-03-16 16:31 ` David Hildenbrand (Arm)
2026-02-27 19:42 ` [PATCHv7 07/18] mm: Rework compound_head() for power-of-2 sizeof(struct page) Kiryl Shutsemau (Meta)
2026-02-27 19:42 ` [PATCHv7 08/18] mm/sparse: Check memmap alignment for compound_info_has_mask() Kiryl Shutsemau (Meta)
2026-03-16 16:33 ` David Hildenbrand (Arm)
2026-02-27 19:42 ` [PATCHv7 09/18] mm/hugetlb: Defer vmemmap population for bootmem hugepages Kiryl Shutsemau (Meta)
2026-03-16 16:48 ` David Hildenbrand (Arm)
2026-03-17 11:28 ` Kiryl Shutsemau
2026-03-17 12:47 ` David Hildenbrand (Arm)
2026-02-27 19:42 ` [PATCHv7 10/18] mm/hugetlb: Refactor code around vmemmap_walk Kiryl Shutsemau (Meta)
2026-02-27 19:42 ` [PATCHv7 11/18] x86/vdso: Undefine CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP for vdso32 Kiryl Shutsemau (Meta)
2026-03-16 16:49 ` David Hildenbrand (Arm)
2026-02-27 19:42 ` [PATCHv7 12/18] mm/hugetlb: Remove fake head pages Kiryl Shutsemau (Meta)
2026-03-05 10:39 ` Vlastimil Babka (SUSE)
2026-03-16 17:01 ` David Hildenbrand (Arm)
2026-03-17 11:47 ` [PATCHv7.1 " Kiryl Shutsemau (Meta)
2026-02-27 19:42 ` [PATCHv7 13/18] mm: Drop fake head checks Kiryl Shutsemau (Meta)
2026-10-26 17:45 ` David Hildenbrand (Arm)
2026-10-26 23:25 ` Kiryl Shutsemau
2026-10-26 23:37 ` David Hildenbrand (Arm)
2026-10-27 11:00 ` Peter Zijlstra
2026-10-27 12:00 ` Kiryl Shutsemau
2026-10-27 12:05 ` David Hildenbrand (Arm)
2026-10-27 12:31 ` Kiryl Shutsemau
2026-10-27 12:47 ` Peter Zijlstra
2026-10-27 12:49 ` Peter Zijlstra
2026-10-27 12:58 ` David Hildenbrand (Arm) [this message]
2026-10-27 13:13 ` Muchun Song
2026-10-27 13:35 ` David Hildenbrand (Arm)
2026-10-27 14:03 ` Muchun Song
2026-10-27 12:13 ` Peter Zijlstra
2026-10-27 12:22 ` Kiryl Shutsemau
2026-10-27 12:29 ` Peter Zijlstra
2026-02-27 19:42 ` [PATCHv7 14/18] hugetlb: Remove VMEMMAP_SYNCHRONIZE_RCU Kiryl Shutsemau (Meta)
2026-02-27 19:42 ` [PATCHv7 15/18] mm/hugetlb: Remove hugetlb_optimize_vmemmap_key static key Kiryl Shutsemau (Meta)
2026-02-27 19:42 ` [PATCHv7 16/18] mm: Remove the branch from compound_head() Kiryl Shutsemau (Meta)
2026-02-27 19:42 ` [PATCHv7 17/18] hugetlb: Update vmemmap_dedup.rst Kiryl Shutsemau (Meta)
2026-02-27 21:08 ` Randy Dunlap
2026-03-02 3:10 ` Muchun Song
2026-03-02 10:56 ` [PATCHv7.1 " Kiryl Shutsemau (Meta)
2026-04-30 3:25 ` patchwork-bot+linux-riscv
2026-02-27 19:42 ` [PATCHv7 18/18] mm/slab: Use compound_head() in page_slab() Kiryl Shutsemau (Meta)
2026-02-28 23:01 ` [PATCHv7 RESEND 00/17] mm: Eliminate fake head pages from vmemmap optimization Andrew Morton
2026-04-30 3:25 ` patchwork-bot+linux-riscv
-- strict thread matches above, loose matches on Subject: below --
2026-02-02 15:56 [PATCHv6 " Kiryl Shutsemau
2026-02-27 19:30 ` [PATCHv7 13/18] mm: Drop fake head checks Kiryl Shutsemau (Meta)
2026-04-30 3:25 ` patchwork-bot+linux-riscv
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