Re: [PATCH v3 04/18] mm/huge_memory: split the routine for splitting anon and file folio

[Kiryl Shutsemau]

On Fri, Aug 21, 2026 at 02:55:17AM +0800, Kairui Song via B4 Relay wrote:
> @@ -4064,7 +4095,6 @@ static int __folio_freeze_and_split_unmapped(struct folio *folio, unsigned int n
>  		folio_put_refs(new_folio, nr_pages);
>  	}
>  
> -	zone_device_private_split_cb(folio, NULL);
>  	/*
>  	 * Unfreeze @folio only after all page cache entries, which
>  	 * used to point to it, have been updated with new folios.

This gave me a pause.

I don't know much about the zone device private thing and I had to dig
to check if such folios are always anon. They are. But it is not obvious
to me why this limitation could not be lifted tomorrow. Nothing in "not
directly addressable by the CPU" implies anon-only.

I would appreciate some explanation in the commit message and maybe
VM_WARN_ON_ONCE_FOLIO(folio_is_device_private(folio), folio) in the file
path to flag surprises.

-- 
  Kiryl Shutsemau / Kirill A. Shutemov