On Mon, Jun 17, 2013 at 02:44:46PM +0800, Fam Zheng wrote:
> Introduce a "drive" option to new image mode. With this mode, QMP command
> should (this patch only modified drive-backup to support it, and report
> invalid
> parameter error for drive-mirror) skip creating the image file or trying to
> open it, it should just reuse the existing BDS by looking for the named drive
> with bdrv_find(). It will be useful to utilize "none" sync mode of
> drive-backup
> for point-in-time snapshot.
>
> The example with drive-backup is:
>
> -> { "execute": "drive-backup", "arguments": { "device": "ide0-hd0",
> "mode": "drive",
> "target": "drive_id_here"
> } }
> <- { "return": {} }
>
>
> Target bs is not released when block job completes in this case since it's
> still used as a device drive or exported by nbd server.
>
> Signed-off-by: Fam Zheng <f...@redhat.com>
> ---
> block/backup.c | 9 ++++++--
> blockdev.c | 57
> ++++++++++++++++++++++++++++++++---------------
> include/block/block_int.h | 3 ++-
> qapi-schema.json | 4 +++-
> 4 files changed, 51 insertions(+), 22 deletions(-)
Fam and I chatted about this yesterday. The QMP API change here is that
traditionally 'target' and 'mode' always referred to existing filenames.
Now you can set 'mode': 'drive' and then 'target' becomes a QEMU block
device name.
I think this API extension is reasonable but I think we haven't nailed
down the lifecycle of the snapshot block drive yet...
Stefan
