Re: [Qemu-devel] [Qemu-block] [PULL 07/14] iotests: Add 241 to test NBD on unaligned images

[Eric Blake <eblake@redhat.com>]

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On 4/10/19 12:45 PM, Max Reitz wrote:
> On 01.04.19 16:08, Eric Blake wrote:
>> Add a test for the NBD client workaround in the previous patch.  It's
>> not really feasible for an iotest to assume a specific tracing engine,
>> so we can't really probe trace_nbd_parse_blockstatus_compliance to see
>> if the server was fixed vs. whether the client just worked around the
>> server (other than by rearranging order between code patches and this
>> test). But having a successful exchange sure beats the previous state
>> of an error message. Since format probing can change alignment, we can
>> use that as an easy way to test several configurations.
>>
>> Not tested yet, but worth adding to this test in future patches: an
>> NBD server that can advertise a non-sector-aligned size (such as
>> nbdkit) causes qemu as the NBD client to misbehave when it rounds the
>> size up and accesses beyond the advertised size. Qemu as NBD server
>> never advertises a non-sector-aligned size (since bdrv_getlength()
>> currently rounds up to sector boundaries); until qemu can act as such
>> a server, testing that flaw will have to rely on external binaries.
>>

>> +++ b/tests/qemu-iotests/241.out

>> +=== Exporting unaligned raw image, forced server sector alignment ===
>> +
>> +WARNING: Image format was not specified for '/home/eblake/qemu/tests/qemu-iotests/scratch/t.raw' and probing guessed raw.
>> +         Automatically detecting the format is dangerous for raw images, write operations on block 0 will be restricted.
>> +         Specify the 'raw' format explicitly to remove the restrictions.
> 
> Is there a patch for this already?

Oh shoot. I saw the complaint about the hard-coded path needing a
filter, and still failed to fix it in time for 4.0-rc3. Not a driver for
-rc4 on its own, but if we have something else pop up that mandates
-rc4, I'll get that fix in.

Will post shortly...

> 
> Also, I planned to reply to the original patch – but where is it?  The
> latest version I can see on the list is v3, and that only has seven
> lines in the reference output.  Well, the difference would explain why
> Vladimir would give a Tested-by to a test that clearly will not run on
> his machine.

Yeah, this line in the commit message is evidence of my botching things:

> [eblake: add forced-512 alignment, and nbdkit reproducer comment]

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


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