[PATCH] arm64: mm: call pagetable dtor when freeing hot-removed page tables

[Kevin Brodsky]

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