Re: [PATCH 2/2] qemu-iotests: Test convert to qcow2 compressed to NBD

[Eric Blake]

On 7/27/20 5:04 AM, Max Reitz wrote:
> On 26.07.20 17:25, Nir Soffer wrote:
> > Add test for "qemu-img convert -O qcow2 -c" to NBD target. The use case
> > is writing compressed disk content to OVA archive.
> >
> > Signed-off-by: Nir Soffer <nsoffer@redhat.com>
> > ---

> > +# The use case is writing qcow2 image directly into a tar file. Code to create
> > +# real tar file not included.
> > +#
> > +# offset    content
> > +# -------------------------------
> > +#      0    first memebr header
>
> *member
>
> > +#    512    first member data
> > +#   1024    second memeber header
>
> *member
>
> > +#   1536    second member data
> > +
> > +tar_file = file_path("test.tar")

I guess it's okay that you don't create a real tar file here, but 
listing the commands to create it (even as a comment) is better than 
just saying "trust me".  And it doesn't seem like that much more work - 
it looks like the key to your test is that you created a tar file 
containing two files, where the first file was less than 512 bytes and 
the second file is your target destination that you will be rewriting.

> > +out = qemu_img_pipe("measure", "-O", "qcow2", "--output", "json", src_disk)
> > +measure = json.loads(out)
> > +qemu_img_create("-f", "raw", tar_file, str(measure["required"]))
>
> Should this be measure["required"] + 1536?

The test works without it (because of compression), but yes, if you are 
going to test writing into an offset, you should oversize your file by 
that same offset.

> > +
> > +nbd_sock = file_path("nbd-sock", base_dir=iotests.sock_dir)
> > +nbd_uri = "nbd+unix:///exp?socket=" + nbd_sock
> > +
> > +# Use raw format to allow creating qcow2 directy into tar file.
> > +qemu_nbd(
> > +    "--socket", nbd_sock,
> > +    "--persistent",
> > +    "--export-name", "exp",
> > +    "--format", "raw",
> > +    "--offset", "1536",
> > +    tar_file)
> > +
> > +iotests.log("=== Target image info ===")
> > +qemu_img_log("info", nbd_uri)
> > +
> > +# Write image into the tar file. In a real applicatio we would write a tar
>
> *application

> > +=== Converted image check ===
> > +No errors were found on the image.
> > +1/160 = 0.62% allocated, 100.00% fragmented, 100.00% compressed clusters
> > +Image end offset: 393216
>
> I hope none of this is fs-dependant.  (I don’t think it is, but who
> knows.  I suppose we’ll find out.)

Indeed - time to see what CI thinks of this.

At any rate, given the urgency of getting pull requests for -rc2 in 
before slamming Peter tomorrow, I'll probably try to touch up the issues 
Max pointed out and queue it today.

--
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3226
Virtualization:  qemu.org | libvirt.org