On Mon, Jan 08, 2018 at 03:41:36PM +0100, Kevin Wolf wrote: > Am 05.01.2018 um 07:55 hat Fam Zheng geschrieben: > > Management and users are accustomed to "qemu-img info" to query status of > > images even when they are used by guests. Since image locking was added, > > the -U > > (--force-share) option is needed for that to work. The reason has been that > > due > > to possible race with image header update, the output can be misleading. > > > > But what are likely to happen after we emit the error are that, for > > interactive > > users, '-U' will be used and the command retried; for management (nova, RHV, > > etc.), the operation is broken with no knob to workaround this. > > > > This series changes that error to a warning so that it doesn't get in the > > way. > > Are management tools actually doing this? There is no good reason to > call 'qemu-img info' for an image that is in use by a VM.
Yes, Nova does use 'qemu-img info' in a few places (haven't audited them all) for a running guest. From a quick look at the code, at-least during Nova's live snaphot (as part of libvirt's "shallow rebase") it is used. > If no, NACK. Automatically disabling locking because it can be > inconvenient defeats the purpose of locking. > > If yes, clearly indicate that this usage is deprecated and we'll turn > this into an error again with 2.13. Then management tools can be fixed > in time. Yes, for completness' sake, Nova upstream is already patched to use the `qemu-img` '--force-share' flag that comes with QEMU >= 2.10. -- /kashyap