Re: [PATCH v4 02/12] mm/rmap: Add try_to_unmap_hugetlb_one

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

On 2026/6/18 15:55, David Hildenbrand (Arm) wrote:
>> 	return __rste_to_pte(pte_val(*ptep));
>> }
>>
>>>> +	VM_WARN_ON(!pte_present(pteval));
>>>> +	subpage = folio_page(folio, pte_pfn(pteval) - folio_pfn(folio));
>>>
>>> No need for subpages.
>>
>> So plain ptep_get() can feed raw huge-entry bits into pte_pfn(), and the
>> derived subpage can be wrong.
> 
> Good question which impact that might have in practice?

The subpage check can warn, but we still pass that subpage to
make_hwpoison_entry(). So the hwpoison marker can end up with the
wrong PFN?

+	subpage = folio_page(folio, pte_pfn(pteval) - folio_pfn(folio));
+	VM_WARN_ON(folio_page(folio, 0) != subpage);
[...]
+	pteval = swp_entry_to_pte(make_hwpoison_entry(subpage));