[pve-devel] applied-series: [PATCH storage/qemu-server v2 0/5] avoid absolute qcow2 references

[Fiona Ebner]

Am 29.07.25 um 1:53 PM schrieb Fabian Grünbichler:
> we don't want qcow2 files to reference their backing chains via
> absolute paths, as that makes renaming the base dir or VG of the storage
> impossible. in most places, qemu already allows simply passing a
> filename as backing-file reference, which will be interpreted as a
> reference relative to the backed image.
> 
> I haven't found any further code paths that trigger absolute references,
> but I might have missed some. the full backing chain should show
> relative backing-file members when queried via
> 
> qemu-img info --output json --format qcow2 --backing-chain /path/to/main/image.qcow2
> 
> such, as:
> 
>         "full-backing-filename": "/var/lib/extsnap/images/210/snap-test2-vm-210-disk-0.qcow2",
>         "backing-filename": "snap-test2-vm-210-disk-0.qcow2",
> 
> note that full-backing-filename will always contain the resolved,
> absolute path and that is okay. we could warn about both members
> containing full paths in `volume_snapshot_info`.
> 
> for existing "broken" images, an "unsafe" rebase with
> 
> qemu-img rebase -u -f qcow2 -F qcow2 -b <relative backing file path> <absolute backed filed path>
> 
> should just rewrite the qcow2 header to replace the backing file
> reference - this should of course not be run while the image is being
> written by other process or QEMU.

Applied series, with the discussed fix-up squashed in, thanks!