On 26.08.19 00:03, Nir Soffer wrote:
> Using block_resize we can test allocate_first_block() with file
> descriptor opened with O_DIRECT, ensuring that it works for any size
> larger than 4096 bytes.
> 
> Testing smaller sizes is tricky as the result depends on the filesystem
> used for testing. For example on NFS any size will work since O_DIRECT
> does not require any alignment.
> ---
>  tests/qemu-iotests/175     | 25 +++++++++++++++++++++++++
>  tests/qemu-iotests/175.out |  8 ++++++++
>  2 files changed, 33 insertions(+)

Thanks for the test!

There’s just one thing: 175 now needs

_default_cache_mode none
_supported_cache_modes none directsync

somewhere near the top (where the rest of _supported*) is.  (Otherwise,
it will fail when the iotests should be run with some other cache mode
instead of being skipped.)

With that added:

Reviewed-by: Max Reitz <mreitz@redhat.com>