[Nbd] NBD: exported files over something around 1 TiB get an insane device size on the client side and are actually empty

[Christoph A. M. <cal...@sc...>]

Hi.

On advice from Alex Bligh I'd like to ping linux-block and nbd-general
about the issue described here:
https://github.com/NetworkBlockDevice/nbd/issues/44

What basically happens is, that with a recent kernel (Linux heisenberg
4.9.0-1-amd64 #1 SMP Debian 4.9.2-2 (2017-01-12) x86_64 GNU/Linux),
when a device larger than something between 1 TiB and 2 TiB is exported
via nbd-server and connected to via nbd-client (which uses the kernel
driver, AFAIU) than the device size gets insanely large while reading
from /dev/nbd0 gives actually nothing.


The bug does not seem to happen when the kernel is not involved (we
tried using nbd-server and qemu-img as the client).

Don't think it makes all too much sense to copy & paste everything from
what was tried already for testing here, so please have a look at the
issue on github.


Best,
Chris.