Re: [PATCH v4 07/11] iomap: fix iomap_dio_zero() for fs bs > system page size

Christoph Hellwig
2024-04-27T04:52:47Z

On Sat, Apr 27, 2024 at 04:26:44AM +0100, Matthew Wilcox wrote:
> There's a series of commits in linux-mm with the titles:
>
> sparc: use is_huge_zero_pmd()
> mm: add is_huge_zero_folio()
> mm: add pmd_folio()
> mm: convert migrate_vma_collect_pmd to use a folio
> mm: convert huge_zero_page to huge_zero_folio
> mm: convert do_huge_pmd_anonymous_page to huge_zero_folio
> dax: use huge_zero_folio
> mm: rename mm_put_huge_zero_page to mm_put_huge_zero_folio
>
> > it available for non-hugetlb setups? Not only would this be cleaner
> > and more efficient, but it would actually work for the case where you'd
> > have to zero more than 1MB on a 4k PAGE_SIZE system, which doesn't
> > seem impossible with 2MB folios.
>
> It is available for non-hugetlb setups. It is however allocated on
> demand, so it might not be available.

We could just export get_huge_zero_page/put_huge_zero_page and make
sure it is is available for block sizse > PAGE_SIZE file systems, or
is there a good argument against that?