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

From: Christoph Hellwig <hch@infradead.org>
To: Matthew Wilcox <willy@infradead.org>
Cc: Christoph Hellwig <hch@infradead.org>,
	"Pankaj Raghav (Samsung)" <kernel@pankajraghav.com>,
	djwong@kernel.org, brauner@kernel.org, david@fromorbit.com,
	chandan.babu@oracle.com, akpm@linux-foundation.org,
	linux-fsdevel@vger.kernel.org, hare@suse.de,
	linux-kernel@vger.kernel.org, linux-mm@kvack.org,
	linux-xfs@vger.kernel.org, mcgrof@kernel.org,
	gost.dev@samsung.com, p.raghav@samsung.com
Subject: Re: [PATCH v4 07/11] iomap: fix iomap_dio_zero() for fs bs > system page size
Date: Fri, 26 Apr 2024 21:52:41 -0700	[thread overview]
Message-ID: <ZiyEmb296SOjXBtS@infradead.org> (raw)
In-Reply-To: <ZixwdKxqYWq4-rxd@casper.infradead.org>

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?