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

[Lance Yang]

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));