Re: [PATCH 1/1] mm/huge_memory: fix pgtable withdrawal for huge zero PMDs

[Lance Yang <lance.yang@linux.dev>]

On 2026/9/15 02:19, Andrew Morton wrote:
> On Mon, 14 Sep 2026 16:29:00 +0200 "David Hildenbrand (Arm)" <david@kernel.org> wrote:
> 
>> On 9/14/26 12:59, Kiryl Shutsemau wrote:
>>> On Sun, Sep 13, 2026 at 03:23:12PM +0800, Lance Yang wrote:
>>>>
>>>> On Sat, Sep 12, 2026 at 11:46:35PM -0700, Andrew Morton wrote:
>>>>>
>>>>>
>>>>> That's the sort of thing we'd prefer to avoid.
>>>>>
>>>>>
>>>>> How real is this?  Is there a reported-by:?  Do you have a reproducer?
>>>>
>>>> Yes, I reproduced it on x86 with a small test module. It sets
>>>> VM_MIXEDMAP | VM_HUGEPAGE and calls vmf_insert_pfn_pmd() with
>>>> huge_zero_pfn, without touching the page tables directly. A full-PMD
>>>> munmap() crashes before the split series[1] as well.
>>>
>>> Ah. So there's no real bug upstream, right?
>>
>> Matches my understanding.
> 
> Thanks.  I'll remove cc:stable, move this into mm-unstable as a
> next-merge-window thing.

Sounds good to me, thanks, Andrew!

Kiryl, David, would you prefer the validation for raw-PFN mappings
of the huge zero page as a separate follow-up, or should that
validation replace this patch? wdyt

Cheers, Lance