Re: [Qemu-devel] [PATCH v3 6/8] blockdev: add DriveBackup transaction

[Stefan Hajnoczi]

On Wed, May 15, 2013 at 01:13:26PM -0600, Eric Blake wrote:
> On 05/15/2013 08:34 AM, Stefan Hajnoczi wrote:
> > This patch adds a transactional version of the drive-backup QMP command.
> > It allows atomic snapshots of multiple drives along with automatic
> > cleanup if there is a failure to start one of the backup jobs.
> > 
> > Note that QMP events are emitted for block job completion/cancellation
> > and the block job will be listed by query-block-jobs.
> > 
> 
> > +
> > +static void drive_backup_abort(BlkTransactionState *common)
> > +{
> > +    DriveBackupState *state = DO_UPCAST(DriveBackupState, common, common);
> > +    BlockDriverState *bs = state->bs;
> > +
> > +    /* Only cancel if it's the job we started */
> > +    if (bs && bs->job && bs->job == state->job) {
> > +        block_job_cancel_sync(bs->job);
> > +    }
> 
> Question - if starting the job created the target file, should aborting
> the job unlink() that file so that we aren't polluting the file system?

blockdev-snapshot-sync action does not delete the file on abort.

> > +++ b/qapi-schema.json
> > @@ -1609,6 +1609,27 @@
> >              '*mode': 'NewImageMode' } }
> >  
> >  ##
> > +# @DriveBackup
> > +#
> > +# @device: the name of the device whose writes should be mirrored.
> > +#
> > +# @target: the target of the new image. If the file exists, or if it
> > +#          is a device, the existing file/device will be used as the new
> > +#          destination.  If it does not exist, a new file will be created.
> > +#
> > +# @format: #optional the format of the new destination, default is to
> > +#          probe if @mode is 'existing', else the format of the source
> > +#
> > +# @mode: #optional whether and how QEMU should create a new image, default 
> > is
> > +#        'absolute-paths'.
> > +#
> > +# @speed: #optional the maximum speed, in bytes per second
> > +##
> 
> Mention "Since: 1.6"

Will add in v4.