I posted a patch[1] to add s390x build for ovirt-imageio, but the build
reveal that direct I/O using 512 bytes alignment does not work on 
the test slave (or maybe this is a platform issue?).

See failing tests:
https://jenkins.ovirt.org/job/ovirt-imageio_standard-check-patch/414/consoleFull

00:05:34.273 [check-patch.fc28.s390x] func = <built-in method readinto of _io.FileIO object at 0x3ff850a2048>
00:05:34.273 [check-patch.fc28.s390x] args = (<mmap.mmap object at 0x3ff85238618>,)
00:05:34.273 [check-patch.fc28.s390x] e = IOError(22, 'Invalid argument')

Increasing the default block size fixes these tests, but cause other test to fail,
because the code is not ready for 4k yet:
https://jenkins.ovirt.org/job/ovirt-imageio_standard-check-patch/415/consoleFull

So adding s390x build requires more work. I open a bug[2] for this work.

We should have 4k support in imageio in 4.3, but I'm not sure we will
have time to work on this before that, unless someone else wants to 
contribute :-)

[1] https://gerrit.ovirt.org/c/94095/
[2] https://bugzilla.redhat.com/1624963

Nir