On Wed, Feb 23, 2022 at 02:33:04PM +0100, Peter Krempa wrote: > On Wed, Feb 23, 2022 at 14:17:40 +0100, Kashyap Chamarthy wrote: > > On Tue, Feb 22, 2022 at 05:55:38PM +0100, Peter Krempa wrote: [...] > > Now to construct a reproducer with `virsh`. Peter, tell me what I got > > wrong :-) > > > > (1) Let's start with this image chain (overlays are always of qcow2 > > format): > > > > base.raw <-- overlay1 <-- overlay2 (live QEMU). > > > > With the goal of copying the above into the below chain (note, here > > we're flattening both base.raw and overlay1 into a single file, > > "flat-o-b1") > > > > flat-o-b1.raw <-- copy (live QEMU) > > > > (2) Make a *raw* variant of "base <-- overlay1", call it "flat-b-o1.raw" > > (i.e. flattened version of combined base and overlay1): > > > > $ qemu-img convert -f qcow2 -O raw overlay1.qcow2 \ > > flat-b-o1.raw > > > > (3) Then, create an empty QCOW2 file to create "flat-b-o1 <-- copy (empty)": > > > > $ qemu-img create -f qcow2 \ > > -o backing_file=flat-b-o1.raw,backing_fmt=raw copy.qcow2 > > > > (4) *Then* perform the `blockcopy --reuse-external --shallow`: > > > > $ virsh blockcopy \ > > --domain vm1 vda ./copy.qcow2 \ > > --wait --verbose --reuse-external --shallow \ > > --finish > > If you are working on a persistent domain/vm use --transient-job to > avoid the need to undefine it. Yeah, makes sense. > Also note that '--finish' is equivalent to aborting the job after it > reaches synchronized phase ... Damn, I thought I _removed_ finish, but still forgot it despite making a mental note. Thanks for catching htat. > > (5) And then pivot the job, so that live QEMU now points to copy > > > > $ virsh blockjob --pivot > > > ... so this will actually say that there is no blockjob, because the > previous step actually cancelled it. Yeah, indeed. > > > > And the final result, we get the "goal" chain in step (1). > > > > src: base <-- overlay1 <-- overlay2 > > == == > > dst: flat-o-b1 <-- copy (live QEMU) > > > > > > Am I missing anything else? > > Now the bug is that when you _cancel_ the job we attempt to blockdev-del > some images which were not blockdev-added, and thus create some spurious > log entries, but the rest of the code behaves correctly. Yep, understood. > So you'll only see the failure this is fixing in the logs. Noted. Thanks for the review. -- /kashyap
