Re: [Qemu-devel] [PATCH 0/2] Don't allow snapshots if the overlay has parent nodes

[Max Reitz <mreitz@redhat.com>]

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On 29.10.2015 14:00, Alberto Garcia wrote:
> There are several sanity checks for the 'blockdev-snapshot' command,
> but none covers the use of a file BDS as the overlay node.
> 
>       { 'execute': 'blockdev-add', 'arguments':
>         { 'options': { 'driver': 'qcow2',
>                        'node-name': 'new0',
>                        'file': { 'driver': 'file',
>                                  'filename': 'new.qcow2',
>                                  'node-name': 'file0' } } } }
> 
>       { 'execute': 'blockdev-snapshot', 'arguments':
>         { 'node': 'virtio0',
>           'overlay': 'file0' } }

Well, I don't think the problem here is that file0 has a parent. For
instance, you might want to use a qcow2 child node of a quorum BDS as
the new overlay; or in the future, you may want to use a snapshot node
which has some filters on top of it.

To me, the problem is that file0 is driven by the driver "file" which
does not support backing files. I think that's what should be fixed.

Max

> This series fixes that and adds a new test case. This of course
> depends on the 'blockdev-snapshot' series:
> 
>    https://lists.gnu.org/archive/html/qemu-block/2015-10/msg00974.html
> 
> I anyway wonder if it wouldn't be a good idea to have regular op
> blockers in all file BDSs?
> 
> Regards,
> 
> Berto
> 
> Alberto Garcia (2):
>   block: Don't allow snapshots if the overlay has parent nodes
>   block: test 'blockdev-snapshot' using a file BDS as the overlay
> 
>  blockdev.c                 |  5 +++++
>  tests/qemu-iotests/085     | 12 +++++++++++-
>  tests/qemu-iotests/085.out |  4 ++++
>  3 files changed, 20 insertions(+), 1 deletion(-)
> 



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