Re: [Qemu-devel] [PATCH for-4.1 2/2] iotests: Test backup job with two guest writes

[Vladimir Sementsov-Ogievskiy]

01.08.2019 20:06, Max Reitz wrote:
> On 01.08.19 18:03, Vladimir Sementsov-Ogievskiy wrote:
>> 01.08.2019 18:12, Max Reitz wrote:
>>> Perform two guest writes to not yet backed up areas of an image, where
>>> the former touches an inner area of the latter.
>>>
>>> Before HEAD^, copy offloading broke this in two ways:
>>> (1) The output differs from the reference output (what the source was
>>>       before the guest writes).
>>> (2) But you will not see that in the failing output, because the job
>>>       offset is reported as being greater than the job length.  This is
>>>       because one cluster is copied twice, and thus accounted for twice,
>>>       but of course the job length does not increase.
>>>
>>> Signed-off-by: Max Reitz <address@hidden>
>>> ---
>>>    tests/qemu-iotests/056     | 34 ++++++++++++++++++++++++++++++++++
>>>    tests/qemu-iotests/056.out |  4 ++--
>>>    2 files changed, 36 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/tests/qemu-iotests/056 b/tests/qemu-iotests/056
>>> index f40fc11a09..d7198507f5 100755
>>> --- a/tests/qemu-iotests/056
>>> +++ b/tests/qemu-iotests/056
>>> @@ -133,6 +133,7 @@ class BackupTest(iotests.QMPTestCase):
>>>            self.vm = iotests.VM()
>>>            self.test_img = img_create('test')
>>>            self.dest_img = img_create('dest')
>>> +        self.ref_img = img_create('ref')
>>>            self.vm.add_drive(self.test_img)
>>>            self.vm.launch()
>>>    
>>> @@ -140,6 +141,7 @@ class BackupTest(iotests.QMPTestCase):
>>>            self.vm.shutdown()
>>>            try_remove(self.test_img)
>>>            try_remove(self.dest_img)
>>> +        try_remove(self.ref_img)
>>>    
>>>        def hmp_io_writes(self, drive, patterns):
>>>            for pattern in patterns:
>>> @@ -177,6 +179,38 @@ class BackupTest(iotests.QMPTestCase):
>>>                self.assert_qmp(event, 'data/error', qerror)
>>>                return False
>>>    
>>> +    def test_overlapping_writes(self):
>>> +        # Write something to back up
>>> +        self.hmp_io_writes('drive0', [('42', '0M', '2M')])
>>> +
>>> +        # Create a reference backup
>>> +        self.qmp_backup_and_wait(device='drive0', format=iotests.imgfmt,
>>> +                                 sync='full', target=self.ref_img)
>>> +
>>> +        # Now to the test backup: We simulate the following guest
>>> +        # writes:
>>> +        # (1) [1M + 64k, 1M + 128k): Afterwards, everything in that
>>> +        #     area should be in the target image, and we must not copy
>>> +        #     it again (because the source image has changed now)
>>> +        #     (64k is the job's cluster size)
>>> +        # (2) [1M, 2M): The backup job must not get overeager.  It
>>> +        #     must copy [1M, 1M + 64k) and [1M + 128k, 2M) separately,
>>> +        #     but not the area in between.
>>> +
>>> +        self.qmp_backup(device='drive0', format=iotests.imgfmt, 
>>> sync='full',
>>> +                        target=self.dest_img, speed=1)
>>> +
>>> +        self.hmp_io_writes('drive0', [('23', '%ik' % (1024 + 64), '64k'),
>>> +                                      ('66', '1M', '1M')])
>>> +
>>> +        # Let the job complete
>>> +        res = self.vm.qmp('block-job-set-speed', device='drive0', speed=0)
>>> +        self.assert_qmp(res, 'return', {})
>>> +        self.qmp_backup_wait('drive0')
>>> +
>>> +        self.assertTrue(iotests.compare_images(self.ref_img, 
>>> self.dest_img),
>>> +                        'target image does not match reference image')
>>> +
>>>        def test_dismiss_false(self):
>>>            res = self.vm.qmp('query-block-jobs')
>>>            self.assert_qmp(res, 'return', [])
>>> diff --git a/tests/qemu-iotests/056.out b/tests/qemu-iotests/056.out
>>> index dae404e278..36376bed87 100644
>>> --- a/tests/qemu-iotests/056.out
>>> +++ b/tests/qemu-iotests/056.out
>>> @@ -1,5 +1,5 @@
>>> -.........
>>> +..........
>>>    ----------------------------------------------------------------------
>>> -Ran 9 tests
>>> +Ran 10 tests
>>>    
>>>    OK
>>>
>>
>> Failed for me:
>> -..........
>> +qemu-img: Could not open 
>> '/work/src/qemu/master/tests/qemu-iotests/scratch/dest.qcow2': Failed to get 
>> shared "write" lock
>> +Is another process using the image 
>> [/work/src/qemu/master/tests/qemu-iotests/scratch/dest.qcow2]?
>> +......F...
>> +======================================================================
>> +FAIL: test_overlapping_writes (__main__.BackupTest)
>> +----------------------------------------------------------------------
>> +Traceback (most recent call last):
>> +  File "056", line 212, in test_overlapping_writes
>> +    'target image does not match reference image')
>> +AssertionError: False is not true : target image does not match reference 
>> image
>> +
>>    ----------------------------------------------------------------------
>>    Ran 10 tests
>>
>> -OK
>> +FAILED (failures=1)
> 
> Hm.  I hoped seeing BLOCK_JOB_COMPLETED would be enough.

The problem is higher: "Failed to get shared "write" lock". Because of this 
iotests.compare_images
can't work. So, because of locking, we need to shutdown qemu before starting 
qemu-img.
And it's done so in test_complete_top() (I just looked at it as it's the only 
other user of compare_images
in 056)

> 
>> So, with applied
>>
>> @@ -207,6 +207,7 @@ class BackupTest(iotests.QMPTestCase):
>>            res = self.vm.qmp('block-job-set-speed', device='drive0', speed=0)
>>            self.assert_qmp(res, 'return', {})
>>            self.qmp_backup_wait('drive0')
>> +        self.vm.shutdown()
>>
>>            self.assertTrue(iotests.compare_images(self.ref_img, 
>> self.dest_img),
>>                            'target image does not match reference image')
> 
> I’d personally prefer auto_dismiss=False and then block-job-dismiss.
> Although I can’t give a reason why.
> 
>> Reviewed-by: Vladimir Sementsov-Ogievskiy <address@hidden>
>> Tested-by: Vladimir Sementsov-Ogievskiy <address@hidden>
> 
> In any case, thanks!
> 
> Max
> 


-- 
Best regards,
Vladimir