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

[Kevin Wolf <kwolf@redhat.com>]

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<vsementsov@virtuozzo.com>
> >>>> ---
> >>>>    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