From: Kevin Brodsky <kevin.brodsky@arm•com>
To: "David Hildenbrand (Arm)" <david@kernel•org>,
Vishal Moola <vishal.moola@gmail•com>,
Catalin Marinas <catalin.marinas@arm•com>
Cc: Andrew Morton <akpm@linux-foundation•org>,
Alistair Popple <apopple@nvidia•com>,
linux-arm-kernel@lists•infradead.org,
linux-kernel@vger•kernel.org, linux-mm@kvack•org,
will@kernel•org
Subject: Re: [PATCH] arm64: mm: call pagetable dtor when freeing hot-removed page tables
Date: Wed, 27 May 2026 09:34:19 +0200 [thread overview]
Message-ID: <db11078b-a283-4717-bed2-da56e77c7132@arm.com> (raw)
In-Reply-To: <1be38262-53de-4a27-9841-393e12fc1475@kernel.org>
On 26/05/2026 14:31, David Hildenbrand (Arm) wrote:
> On 5/26/26 13:54, Kevin Brodsky wrote:
>> On 22/05/2026 11:36, Vishal Moola wrote:
>>>> diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
>>>> index 4c8959153ac4..9d42cbddce27 100644
>>>> --- a/arch/arm64/mm/mmu.c
>>>> +++ b/arch/arm64/mm/mmu.c
>>>> @@ -1441,6 +1441,9 @@ static void free_hotplug_page_range(struct page *page, size_t size,
>>>>
>>>> static void free_hotplug_pgtable_page(struct page *page)
>>>> {
>>>> + if (folio_test_pgtable(page_folio(page)))
>>> This should work.
>>>
>>>> + pagetable_dtor(page_ptdesc(page));
>>>> +
>>>> free_hotplug_page_range(page, PAGE_SIZE, NULL);
>>> In the case we presumably have a page table page (ptdesc) at this
>>> point, we should really be freeing it with pagetable_free() as well.
>> Agreed, I think this is the right thing to do, something like:
>>
>> if (folio_test_pgtable(page_folio(page)))
>> pagetable_dtor_free(page_ptdesc(page)); else
>> free_hotplug_page_range(page, PAGE_SIZE, NULL);
> That code pattern is wrong.
>
> folio_test_pgtable() shouldn't exist.
>
> In the future, something is either a pgtable or a folio, not both.
>
> So check the type against the page, not the folio.
In other words use PageTable(page) instead? Interestingly I can see a
few calls to folio_test_pgtable() across the kernel but none to
PageTable(), maybe just an antipattern then? The ctor/dtor also use
__folio_{set,clear}_pgtable().
- Kevin
next prev parent reply other threads:[~2026-05-27 7:34 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-05-21 3:27 [PATCH] arm64: mm: call pagetable dtor when freeing hot-removed page tables Alistair Popple
2026-05-21 22:31 ` Andrew Morton
2026-05-21 23:50 ` Alistair Popple
2026-05-22 7:15 ` Catalin Marinas
2026-05-22 7:32 ` Catalin Marinas
2026-05-22 9:36 ` Vishal Moola
2026-05-26 11:54 ` Kevin Brodsky
2026-05-26 12:31 ` David Hildenbrand (Arm)
2026-05-27 7:34 ` Kevin Brodsky [this message]
2026-05-27 9:22 ` Vishal Moola
2026-05-31 19:29 ` David Hildenbrand (Arm)
2026-05-26 15:07 ` Will Deacon
2026-05-27 7:35 ` Kevin Brodsky
2026-05-27 9:30 ` Vishal Moola
2026-05-28 8:05 ` Kevin Brodsky
2026-05-29 10:16 ` Vishal Moola
2026-06-02 4:22 ` Andrew Morton
2026-06-02 13:12 ` Will Deacon
2026-06-02 17:06 ` Andrew Morton
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