Il 17/07/2013 14:58, Kevin Wolf ha scritto: > Am 17.07.2013 um 14:36 hat Paolo Bonzini geschrieben: >> Il 17/07/2013 11:42, Fam Zheng ha scritto: >>> This option allows overriding backing hd of drive. If the target drive >>> exists, it's referenced as the backing file and refcount incremented. >>> >>> Example: >>> qemu-system-x86_64 -drive \ >>> file.filename=foo.qcow2,if=none,id=foo \ >>> -drive file=bar.qcow2,backing=foo >> >> I guess this is where we need the soft reference. >> >> This has a _lot_ of potential for misuse, I think Kevin bashed me and >> Federico very heavily when we tried to do something similar. > > Not sure what exactly I "bashed" you for
Doing strange things with bs->backing_hd (blkmirror comes to mind). > This is basically restarting the discussion where I suggested to give > the targets of a block job names so that they can be reused. It's about > the same kind of misuse that becomes possible and that we need to > protect against. Yes. But then I'm not sure why we need to rush in blockdev-backup now. Instead we can simply make drive-backup optionally give a name to the target. I understand this is the right thing to do long term, but pre-opening of the target is not really needed for fleecing. Paolo