Re: [Qemu-devel] [PATCH 3/10] Add bdrv_flush_all()

Paul Brook
2008-09-10T16:37:21Z

> I'm actually liking bdrv_flush_all() less and less. If there are any
> outstanding IO requests, it will increase the down time associated with
> live migration. I think we definitely need to add a live save handler
> that waits until there are no outstanding IO requests to converge. I'm
> concerned though that it's not totally unreasonable to expect a guest to
> always have an IO request in flight. That leads me to think that maybe
> we should be cancelling outstanding requests, and somehow saving their
> state?

That's not possible with the current code because the IO callbacks
(particularly when you start involving the SCSI layer) are generated
dynamically.

Paul