Re: [PATCH v2] nbd/server: Allow MULTI_CONN for shared writable exports

[Eric Blake]

On Wed, Feb 16, 2022 at 11:08:06AM +0300, Vladimir Sementsov-Ogievskiy wrote:
> 16.02.2022 02:24, Eric Blake wrote:

> > > > +++ b/tests/qemu-iotests/tests/nbd-multiconn
> > > > @@ -0,0 +1,188 @@
> > > > +#!/usr/bin/env bash
> > > > +# group: rw auto quick
> > > > +#
> > > > +# Test that qemu-nbd MULTI_CONN works
> > > > +#
> > > > +echo
> > > > +echo "=== Initial image setup ==="
> > > > +echo
> > > > +
> > > > +_make_test_img 4M
> > > > +$QEMU_IO -c 'w -P 1 0 2M' -c 'w -P 2 2M 2M' "$TEST_IMG" | 
> > > > _filter_qemu_io
> > > > +_launch_qemu 2> >(_filter_nbd)
> > > > +_send_qemu_cmd $QEMU_HANDLE '{"execute":"qmp_capabilities"}' "return"
> > > > +_send_qemu_cmd $QEMU_HANDLE '{"execute":"blockdev-add",
> > > > +  "arguments":{"driver":"qcow2", "node-name":"n",
> > > > +    "file":{"driver":"file", "filename":"'"$TEST_IMG"'"}}}' "return"
> > 
> > I'm not the best at writing python iotests; I welcome a language
> > translation of this aspect.
> 
> 
> 
> Let me try:)
> 
> 
> #!/usr/bin/env python3
> 
> import os
> import iotests
> import nbd
> from iotests import qemu_img_create, qemu_io_silent
> 
> 
> disk = os.path.join(iotests.test_dir, 'disk')
> size = '4M'
> nbd_sock = os.path.join(iotests.test_dir, 'nbd_sock')
> nbd_uri = 'nbd+unix:///{}?socket=' + nbd_sock

...

Thanks; I'm playing with this (and the improvements suggested in
followup messages) in preparation for a v3 posting.

> > > > +nbdsh -u "nbd+unix:///r?socket=$nbd_unix_socket" -c '
> > > > +assert h.can_multi_conn()
> > > > +h.shutdown()
> > > > +print("nbdsh passed")'
> > > > +nbdsh -u "nbd+unix:///w?socket=$nbd_unix_socket" -c '
> > > > +assert not h.can_multi_conn()
> > > > +h.shutdown()
> > > > +print("nbdsh passed")'
> > > > 
> > > 
> > > Mixing of shell and python is very confusing. Wouldn't it be much cleaner
> > > to write the test in python?
> > 
> > Here, nbdsh -c 'python snippet' is used as a shell command line
> > parameter.  Writing python code to call out to a system() command
> > where one of the arguments to that command is a python script snippet
> > is going to be just as annoying as writing it in bash.

Then again, since libnbd already includes python bindings, we wouldn't
have to detour through nbdsh, but just use the python bindings
directly (and I see that your translation did that).

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3266
Virtualization:  qemu.org | libvirt.org