Re: [PATCH v3 20/20] mm: stop maintaining the per-page mapcount of large folios (CONFIG_NO_PAGE_MAPCOUNT)

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From: Matthew Wilcox

Date: Tue Oct 14 2025 - 10:32:47 EST

On Tue, Oct 14, 2025 at 02:59:30PM +0200, David Hildenbrand wrote:
> > As commit 349994cf61e6 mentioned, we don't support partially mapped PUD-sized
> > folio yet.
>
> We do support partially mapped PUD-sized folios I think, but not anonymous
> PUD-sized folios.

I don't think so? The only mechanism I know of to allocate PUD-sized
chunks of memory is hugetlb, and that doesn't permit partial mappings.