On 06/18/2015 06:50 PM, Stefan Hajnoczi wrote:
> On Thu, Jun 18, 2015 at 04:49:09PM +0800, Wen Congyang wrote:
>> Usage:
>> -drive file=xxx,id=Y, \
>> -drive
>> file=xxxx,id=X,backing_reference.drive_id=Y,backing_reference.hidden-disk.*
>>
>> It will create such backing chain:
>> {virtio-blk dev 'Y'}
>> {virtio-blk dev 'X'}
>> |
>> |
>> |
>> |
>> v
>> v
>>
>> [base] <- [mid] <- ( Y ) <----------------- (hidden target)
>> <--------------- ( X )
>>
>> v ^
>> v ^
>> v ^
>> v ^
>> >>>> drive-backup sync=none >>>>
>>
>> X's backing file is hidden-disk, and hidden-disk's backing file is Y.
>> Disk Y may be opened or reopened in read-write mode, so A block backup
>> job is automatically created: source is Y and target is hidden disk.
>> Active disk X, hidden disk, and Y are all on the same AioContext.
>
> The command-line option name confused me. I expected "backing_reference" to
> result in:
>
> Y <- X
So if I want to create
Y <- hidden-disk <- X
The command line can be
backing.file.filename=xxx,backing.driver=xxx,backing.backing.backing_reference=Y
>
> The backup block job and hidden target makes this option more than just
> referencing the backing device.
>
> The name "backing.backup-reference" is clearer to me, but I think Kevin
> might have more idea for you on this patch.
>
Any suggestion is welcome.
Thanks
Wen Congyang
