Re: [Qemu-block] [PATCH v5 24/27] iotests: Disable image locking in 085

[Max Reitz]

On 17.05.2016 09:35, Fam Zheng wrote:
> The cases is about live snapshot features. Disable image locking because
> otherwise a few tests are going to fail because we reuse the same images
> at blockdev-add.
> 
> Signed-off-by: Fam Zheng <address@hidden>
> ---
>  tests/qemu-iotests/085 | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/tests/qemu-iotests/085 b/tests/qemu-iotests/085
> index aa77eca..48f6684 100755
> --- a/tests/qemu-iotests/085
> +++ b/tests/qemu-iotests/085
> @@ -102,6 +102,7 @@ function add_snapshot_image()
>      cmd="{ 'execute': 'blockdev-add', 'arguments':
>             { 'options':
>               { 'driver': 'qcow2', 'node-name': 'snap_${1}', ${extra_params}
> +               'lock-mode': 'off',
>                 'file':
>                 { 'driver': 'file', 'filename': '${snapshot_file}',
>                   'node-name': 'file_${1}' } } } }"
> @@ -130,7 +131,7 @@ echo === Running QEMU ===
>  echo
>  
>  qemu_comm_method="qmp"
> -_launch_qemu -drive file="${TEST_IMG}.1",if=virtio -drive 
> file="${TEST_IMG}.2",if=virtio
> +_launch_qemu -drive file="${TEST_IMG}.1",if=virtio,lock-mode=off -drive 
> file="${TEST_IMG}.2",if=virtio,lock-mode=off
>  h=$QEMU_HANDLE
>  
>  echo
> 

So as far as I understand it, add_snapshot_image() is supposed to add
images from the backing chain to the running VM. The top image is never
used by add_snapshot_image(), thus the lock-mode=off in the QEMU command
line seems superfluous.

Since the backing chain is opened read-only by the VM, it is locked in
shared mode, basically. Therefore, we can simply use explicitly shared
lock mode in add_snapshot_image(); or, alternatively, it is completely
sufficient to specify "'read-only': true" there instead of forcing a
non-exclusive locking mode.

And indeed, for me the test passes if I undo the changes done by this
patch and just insert said "'read-only': true" in the blockdev-add
invocation done by add_snapshot_image().

Max

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