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Date: Tue, 27 Jun 2017 14:20:40 +0100
From: "Daniel P. Berrange" <berrange@redhat.com>
Message-ID: <20170627132040.GH13634@redhat.com>
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Subject: Re: [Qemu-devel] [PATCH 1/4] block/qcow2: add compression_algorithm
 create option
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To: Peter Lieven <pl@kamp.de>
Cc: qemu-block@nongnu.org, kwolf@redhat.com, qemu-devel@nongnu.org, mreitz@redhat.com, den@openvz.org, lersek@redhat.com

On Tue, Jun 27, 2017 at 02:34:07PM +0200, Peter Lieven wrote:
> this patch adds a new compression_algorithm option when creating qcow2 images.
> The current default for the compresison algorithm is zlib and zlib will be
> used when this option is omitted (like before).
> 
> If the option is specified e.g. with:
> 
>  qemu-img create -f qcow2 -o compression_algorithm=zlib image.qcow2 1G

IMHO we should introduce a nested struct "compress" struct to hold the format
name, and any other format specific arguments, in a way that maps nicely to
any future QAPI representmatch of create options. eg

{ 'enum': 'BlockdevQcow2CompressFormat',
  'data': [ 'zlib', 'lzo' ] }

{ 'union': 'BlockdevQcow2Compress',
  'base': { 'format': 'BlockdevQcow2CompressFormat' },
  'discriminator': 'format',
  'data': { 'zlib': 'BlockdevQcow2CompressZLib',
            'lzo': 'BlockdevQcow2CompressLZO'} }

so it would map to

 qemu-img create -f qcow2 -o compress.format=zlib image.qcow2 1G

and let us have other compress.XXXX options specific to each format

Regards,
Daniel
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