Re: [PATCH v4] fstests: generic: add a test case to check fsverity reads

[Eric Biggers <ebiggers@kernel.org>]

On Sat, Oct 17, 2026 at 07:33:41PM +1030, Qu Wenruo wrote:
> There is a bug report that with the recently enabled large folios
> support, fsverity enabled files on btrfs can trigger reproducible
> warnings about file corruption, but in the end no error is returned to
> user space.
> 
> It turns out to be a bug in the btrfs fsverity integration, where blocks
> not included in the read range are passed to be verified.
> 
> This is a long-standing bug where btrfs fsverity always assumed that one
> folio contains exactly one fs block, ignoring the fact that btrfs had
> block size < page size support before fsverity support was added.
> 
> Add a new regression test case for it. The workload is pretty simple:
> 
> - Create a 32M file
> 
> - Punch a 64K hole for every 128K
>   This will limit the read bio size to 64K, which is smaller than
>   a lot of large folios, and thus can trigger the btrfs bug.
> 
> - Enable fsverity digest and drop page cache
> 
> - Read that file and verify its content
> 
> - Verify there is no "FILE CORRUPTED!" warning
> 
> Signed-off-by: Qu Wenruo <wqu@suse.com>
> ---

Reviewed-by: Eric Biggers <ebiggers@kernel.org>

- Eric