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

Christoph Hellwig
2024-04-26T06:22:38Z

On Thu, Apr 25, 2024 at 01:37:42PM +0200, Pankaj Raghav (Samsung) wrote:
> From: Pankaj Raghav <p.raghav@samsung.com>
>
> iomap_dio_zero() will pad a fs block with zeroes if the direct IO size
> < fs block size. iomap_dio_zero() has an implicit assumption that fs block
> size < page_size. This is true for most filesystems at the moment.
>
> If the block size > page size, this will send the contents of the page
> next to zero page(as len > PAGE_SIZE) to the underlying block device,
> causing FS corruption.
>
> iomap is a generic infrastructure and it should not make any assumptions
> about the fs block size and the page size of the system.

So what happened to the plan to making huge_zero_page a folio and have
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.