b6fefb03ba
There are multiple reasons to disallow disabling 'snapshot-as-volume-chain' while a qcow2 image exists: 1. The list of allowed formats depends on 'snapshot-as-volume-chain'. 2. Snapshot functionality is broken. This includes creating snapshots, but also rollback, which removes the current volume and then fails. 3. There already is coupling between having qcow2 on LVM and having 'snapshot-as-volume-chain' enabled. For example, the 'discard-no-unref' option is required for qcow2 on LVM, but qemu-server only checks for 'snapshot-as-volume-chain' to avoid hard-coding LVM. Another one is that volume_qemu_snapshot_method() returns 'mixed' when the format is qcow2 even when 'snapshot-as-volume-chain' is disabled. Hunting down these corner cases just to make it easier to disable does not seem to be worth it, considering there's already 1. and 2. as reasons too. 4. There might be other similar issues that have not surfaced yet, because disabling the feature while qcow2 is present is essentially untested and very uncommon. For file-based storages, the 'snapshot-as-volume-chain' property is already fixed, i.e. is determined upon storage creation. Signed-off-by: Fiona Ebner <f.ebner@proxmox.com>