On 05/27/2015 08:31 PM, Kevin Wolf wrote: > Am 21.05.2015 um 07:47 hat Wen Congyang geschrieben: >> On 05/09/2015 01:21 AM, Kevin Wolf wrote: >>> For bs->file, using references to existing BDSes has been possible for a >>> while already. This patch enables the same for bs->backing_hd. >> >> 1. We reference to an existing BDSes, and some disk uses this blk. Do >> we allow this? > > Currently yes. If it breaks, you get to keep both pieces. > > As long as your guest device is read-only, it should just work. It would > be a very bad idea, though, to write to a backing file. > > Op blockers should eventually prevent this from happening (Jeff, you may > want to take a note ;-)) > >> 2. bs->backing_hd->blk can be not NULL now? If we do an active commit >> to this backing file(use mirror job), we will call bdrv_swap() in >> mirror_exit(), and the function bdrv_swap() doesn't allow that >> new_bs->blk(here is bs->backing_hd) is not NULL. > > You're right. > > I can remove this patch from the series for now, but of course that > doesn't solve the problem. I'm not sure what to do about it. Making > bdrv_swap() work with BDSes that have BB attached is probably another > item in the list of "dynamic reconfiguration" problems.
What does "dynamic reconfiguration" mean? Allow to change drive's option when guest is running? Thanks Wen Congyang > > Markus, any ideas? > > Kevin > . >
