On 26.09.19 17:03, Vladimir Sementsov-Ogievskiy wrote:
> 20.09.2019 18:28, Max Reitz wrote:
>> Signed-off-by: Max Reitz <mre...@redhat.com>
>> ---
>> tests/qemu-iotests/041 | 152 +++++++++++++++++++++++++++++++++++++
>> tests/qemu-iotests/041.out | 4 +-
>> 2 files changed, 154 insertions(+), 2 deletions(-)
>>
>> diff --git a/tests/qemu-iotests/041 b/tests/qemu-iotests/041
>> index e4cc829fe2..6ea4764ae8 100755
>> --- a/tests/qemu-iotests/041
>> +++ b/tests/qemu-iotests/041
>> @@ -1265,6 +1265,158 @@ class TestReplaces(iotests.QMPTestCase):
>>
>> self.vm.assert_block_path('filter0/file', 'target')
>>
>> + '''
>> + See what happens when the @sync/@replaces configuration dictates
>> + creating a loop.
>> + '''
>> + def test_loop(self):
>> + qemu_img('create', '-f', iotests.imgfmt, test_img, str(1 * 1024 *
>> 1024))
>> +
>> + # Dummy group so we can create a NOP filter
>> + result = self.vm.qmp('object-add', qom_type='throttle-group',
>> id='tg0')
>> + self.assert_qmp(result, 'return', {})
>> +
>> + result = self.vm.qmp('blockdev-add', **{
>> + 'driver': 'throttle',
>> + 'node-name': 'source',
>> + 'throttle-group': 'tg0',
>> + 'file': {
>> + 'driver': iotests.imgfmt,
>> + 'node-name': 'filtered',
>> + 'file': {
>> + 'driver': 'file',
>> + 'filename': test_img
>> + }
>> + }
>> + })
>> + self.assert_qmp(result, 'return', {})
>> +
>> + # Block graph is now:
>> + # source[throttle] --file--> filtered[qcow2] --file--> ...
>
> or qed, actually
Yep.
>> +
>> + result = self.vm.qmp('drive-mirror', job_id='mirror',
>> device='source',
>> + target=target_img, format=iotests.imgfmt,
>> + node_name='target', sync='none',
>> + replaces='filtered')
>> +
>> + '''
>> + Block graph before mirror exits would be (ignoring mirror_top):
>> + source[throttle] --file--> filtered[qcow2] --file--> ...
>> + target[qcow2] --file--> ...
>> +
>> + Then, because of sync=none and drive-mirror in absolute-paths mode,
>> + the source is attached to the target:
>> + source[throttle] --file--> filtered[qcow2] --file--> ...
>> + ^
> |
>> + backing
>> + |
>> + target[qcow2] --file--> ...
>> +
>> + Replacing filtered by target would yield:
>> + source[throttle] --file--> target[qcow2] --file--> ...
>> + ^ |
>> + +------- backing --------+
>> +
>> + I.e., a loop. bdrv_replace_node() detects this and simply
>> + does not let source's file link point to target. However,
>> + that means that target cannot really replace source.
>> +
>> + drive-mirror should detect this and not allow this case.
>> + '''
>> +
>> + self.assert_qmp(result, 'error/desc',
>> + "Replacing 'filtered' by 'target' with this sync "
>> + \
>> + "mode would result in a loop, because the former "
>> + \
>> + "would be a child of the latter's backing file " + \
>> + "('source') after the mirror job")
>> +
>> + '''
>> + Test what happens when there would be no loop with the pre-mirror
>> + configuration, but something changes during the mirror job that asks
>> + for a loop to be created during completion.
>> + '''
>> + def test_loop_during_mirror(self):
>> + qemu_img('create', '-f', iotests.imgfmt, test_img, str(1 * 1024 *
>> 1024))
>> +
>> + result = self.vm.qmp('blockdev-add', **{
>> + 'driver': 'null-co',
>> + 'node-name': 'common-base',
>> + 'read-zeroes': True,
>
> why do you need read-zeroes?
It’s my understanding that we’d better always set it to true.
>> + 'size': 1 * 1024 * 1024
>> + })
>> + self.assert_qmp(result, 'return', {})
>> +
>> + result = self.vm.qmp('blockdev-add', **{
>> + 'driver': 'copy-on-read',
>> + 'node-name': 'source',
>> + 'file': 'common-base'
>> + })
>> + self.assert_qmp(result, 'return', {})
>
> Hmm, why don't you create them both in one query?
No good reason, I think.
>> +
>> + '''
>
> the following is hard to read without some hint like, "We are going to ..."
I’ll see what I can come up with.
>> + x-blockdev-change can only add children to a quorum node that
>> + have no parent yet, so we need an intermediate node between
>> + target and common-base that has no parents other than target.
>> + We cannot use any parent that would forward the RESIZE
>> + permission (because the job takes it, but unshares it on the
>> + source), so we make it a backing child of a qcow2 node.
>> + Unfortunately, we cannot add backing files to Quorum nodes
>> + (because of an op blocker), so we put another raw node between
>> + the qcow2 node and common-base.
>> + '''
>> + result = self.vm.qmp('blockdev-add', **{
>> + 'driver': 'qcow2',
>> + 'node-name': 'base-parent',
>> + 'file': {
>> + 'driver': 'file',
>> + 'filename': test_img
>> + },
>> + 'backing': {
>> + 'driver': 'raw',
>> + 'file': 'common-base'
>> + }
>> + })
>> +
>> + # Add a quorum node with a single child, we will add
>> + # base-parent to prepare a loop later
>> + result = self.vm.qmp('blockdev-add', **{
>> + 'driver': 'quorum',
>
> It would be good to skip test-cases if quorum unsupported, like other
> test-cases
> with quorum.
Will do.
>> + 'node-name': 'target',
>> + 'vote-threshold': 1,
>> + 'children': [
>> + {
>> + 'driver': 'null-co',
>> + 'read-zeroes': True
>> + }
>> + ]
>> + })
>> + self.assert_qmp(result, 'return', {})
>
> It would be nice to comment out current block graph here...
OK.
>> +
>> + result = self.vm.qmp('blockdev-mirror', job_id='mirror',
>> + device='source', target='target', sync='full',
>> + replaces='common-base')
>> + self.assert_qmp(result, 'return', {})
>> +
>> + result = self.vm.qmp('x-blockdev-change',
>> + parent='target', node='base-parent')
>> + self.assert_qmp(result, 'return', {})
>> +
>> + '''
>
> and here, like you do in previous test-case. And here it even nicer, as this
> test-case
> is more complex.
OK.
>> + This asks for this configuration post-mirror:
>> +
>> + source -> target (replaced common-base) -> base-parent
>> + ^ |
>> + | v
>> + +----------------- [raw]
>> +
>> + bdrv_replace_node() would not allow such a configuration, but
>> + we should not pretend we can create it, so the mirror job
>> + should fail during completion.
>> + '''
>> +
>> + self.complete_and_wait('mirror',
>> + completion_error='Operation not permitted')
>> +
>> if __name__ == '__main__':
>> iotests.main(supported_fmts=['qcow2', 'qed'],
>> supported_protocols=['file'])
>> diff --git a/tests/qemu-iotests/041.out b/tests/qemu-iotests/041.out
>> index 877b76fd31..20a8158b99 100644
>> --- a/tests/qemu-iotests/041.out
>> +++ b/tests/qemu-iotests/041.out
>> @@ -1,5 +1,5 @@
>> -..............................................................................................
>> +................................................................................................
>> ----------------------------------------------------------------------
>> -Ran 94 tests
>> +Ran 96 tests
>>
>> OK
>>
>
>
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