On Tue, May 31, 2016 at 12:15:27PM +0300, Denis V. Lunev wrote:
> From: Pavel Butsykin <pbutsykin@virtuozzo.com>
> 
> The idea is simple - backup is "written-once" data. It is written block
> by block and it is large enough. It would be nice to save storage
> space and compress it.
> 
> The patch adds a flag to the qmp/hmp drive-backup command which enables
> block compression. Compression should be implemented in the format driver
> to enable this feature.
> 
> There are some limitations of the format driver to allow compressed writes.
> We can write data only once. Though for backup this is perfectly fine.
> These limitations are maintained by the driver and the error will be
> reported if we are doing something wrong.
> 
> Signed-off-by: Pavel Butsykin <pbutsykin@virtuozzo.com>
> Signed-off-by: Denis V. Lunev <den@openvz.org>
> CC: Jeff Cody <jcody@redhat.com>
> CC: Markus Armbruster <armbru@redhat.com>
> CC: Eric Blake <eblake@redhat.com>
> CC: John Snow <jsnow@redhat.com>
> CC: Stefan Hajnoczi <stefanha@redhat.com>
> CC: Kevin Wolf <kwolf@redhat.com>
> ---
>  block/backup.c            | 13 +++++++++++++
>  blockdev.c                | 12 ++++++++++--
>  hmp-commands.hx           |  8 +++++---
>  hmp.c                     |  3 ++-
>  include/block/block_int.h |  1 +
>  qapi/block-core.json      |  5 ++++-
>  qmp-commands.hx           |  5 ++++-
>  7 files changed, 39 insertions(+), 8 deletions(-)

Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>