Re: [PATCH v2 5/9] mm/huge_memory: mark PMD mappings of the huge zero folio special

Wei Yang
2025-07-28T08:49:58Z

On Thu, Jul 17, 2025 at 01:52:08PM +0200, David Hildenbrand wrote:
>The huge zero folio is refcounted (+mapcounted -- is that a word?)
>differently than "normal" folios, similarly (but different) to the ordinary
>shared zeropage.
>
>For this reason, we special-case these pages in
>vm_normal_page*/vm_normal_folio*, and only allow selected callers to
>still use them (e.g., GUP can still take a reference on them).
>
>vm_normal_page_pmd() already filters out the huge zero folio. However,
>so far we are not marking it as special like we do with the ordinary
>shared zeropage. Let's mark it as special, so we can further refactor
>vm_normal_page_pmd() and vm_normal_page().
>
>While at it, update the doc regarding the shared zero folios.
>
>Reviewed-by: Oscar Salvador <osalvador@suse.de>
>Signed-off-by: David Hildenbrand <david@redhat.com>

Reviewed-by: Wei Yang <richard.weiyang@gmail.com>

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Wei Yang
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