Re: [Qemu-devel] [PATCH v2 2/2] iotests: simple mirror test with kvm on 1G image

[Vladimir Sementsov-Ogievskiy]

30.11.2018 17:10, Kevin Wolf wrote:
> Am 30.11.2018 um 14:48 hat Vladimir Sementsov-Ogievskiy geschrieben:
>> 30.11.2018 16:13, Max Reitz wrote:
>>> On 30.11.18 14:06, Vladimir Sementsov-Ogievskiy wrote:
>>>> 30.11.2018 15:30, Max Reitz wrote:
>>>>> On 29.11.18 11:18, Vladimir Sementsov-Ogievskiy wrote:
>>>>>> This test is broken without previous commit fixing dead-lock in mirror.
>>>>>>
>>>>>> Signed-off-by: Vladimir Sementsov-Ogievskiy<address@hidden>
>>>>>> ---
>>>>>>     tests/qemu-iotests/235     | 59 
>>>>>> ++++++++++++++++++++++++++++++++++++++
>>>>>>     tests/qemu-iotests/235.out |  1 +
>>>>>>     tests/qemu-iotests/group   |  1 +
>>>>>>     3 files changed, 61 insertions(+)
>>>>>>     create mode 100755 tests/qemu-iotests/235
>>>>>>     create mode 100644 tests/qemu-iotests/235.out
>>>>> I'll get to the first patch in a second, but first a suggestion for this
>>>>> patch: I think it's not so good to use 2 GB of space for a test (1 GB
>>>>> for the source, 1 GB for the target).  So I tried my luck and found that
>>>>> the test works, too, if you just use preallocation=metadata for the
>>>>> source (instead of actually writing data) and blockdev-mirror'ing the
>>>>> data to a throttled null-co device.
>>>>
>>>> Hmm, so parsing metadata is enough for qcow2 to yield on write, yes?
>>>
>>> Apparently so.  If you can confirm that applying those changes to the
>>> test still make it work (i.e., fail before patch 1, pass afterwards),
>>> then I think it is just as good.
>>
>> Ok, I've checked that your changes works for me.
>>
>> hm, but we write to null, so, yield on write comes from throttling, however,
>> without preallocation=metadata, it don't work.., do you know, why we need
>> preallocation to reproduce?
> 
> If I should take a guess, probably because mirror only copies allocated
> clusters?
> 
> Kevin
> 

hm, so, what preallocation=metadata does? I thought, it preallocates tables, 
but all qcow2 clusters would be unallocated..


-- 
Best regards,
Vladimir