Re: [Qemu-devel] live block copy/stream/snapshot discussion

[Kevin Wolf <kwolf@redhat.com>]

Am 14.07.2011 12:00, schrieb Stefan Hajnoczi:
> On Thu, Jul 14, 2011 at 10:55 AM, Kevin Wolf <kwolf@redhat.com> wrote:
>> Am 14.07.2011 11:39, schrieb Stefan Hajnoczi:
>>>  Events:
>>>
>>>  On completion the BLOCK_STREAM_COMPLETED event is raised with the following
>>>  fields:
>>>
>>>  - device: device name (json-string)
>>>  - len:    size of the device, in bytes (json-int)
>>>  - offset: last offset of completed I/O, in bytes (json-int)
>>>  - error:  error message (json-string, only on error)
>>>
>>>  The completion event is raised both on success and on failure.
>>
>> Why do len/offset matter in a completion event?
> 
> For completeness.  You could see it as telling you how much progress
> was made before an error occurred.  In the success case offset will
> always be equal to len.  But in the error case you get the last
> completed progress before error, which could be useful (for example if
> you weren't polling but want to display "Streaming virtio-blk0 failed
> at 33%").

Makes sense.

We also need to define the possible error messages, and probably use an
enum instead of a string.

Kevin