What were you trying to do that didn't work?

Cold migration of Fedora 43 guests from vSphere 8.0.3 to KubeVirt fails during the ImageConversion stage. The failure occurs specifically when virt-v2v attempts to inspect the Btrfs root volume on the guest. While the initial inspection (inspect_os) identifies the Btrfs subvolumes correctly, a subsequent call to inspect_get_format triggers a filesystem mismatch error followed by fatal disk I/O errors.

What is the impact of this issue to you?

Please provide the package NVR for which the bug is seen: 

virt-v2v-2.8.1-13.el10_1

libguestfs-1.56.1-3.el10

kernel-6.12.0-124.8.1.el10_1.x86_64

libvirt-11.5.0-1.el10

How reproducible is this bug?:

While multiple identical Fedora 43 VMs were migrated, failures were intermittent or persistent across specific batches, suggesting a potential edge case in the recent Btrfs implementation within virt-v2v

Steps to reproduce

1. Initiate a cold migration of a Fedora 43 VM (default Btrfs partitioning) from vSphere to KubeVirt using MTV/Forklift.
2. Observe the migration progress until it reaches the ImageConversion task.
3. The conversion fails with "Guest conversion failed".

Expected results

The virt-v2v process should successfully recognize the Btrfs volume format and complete the conversion of the guest image.

Actual results

The conversion process terminates with the following error chain in the logs:

• guestfsd: error: inspect_get_format_stub: btrfsvol:/dev/sdb4/root: expecting a btrfs volume

• virt-v2v-in-place: error: libguestfs error: inspect_get_format: inspect_get_format_stub: btrfsvol:/dev/sdb4/root: expecting a btrfs volume

• [43.987165] I/O error, dev sdb, sector 0 op 0x1:(WRITE) flags 0x800 phys_seg 0 prio class 0

• fsync: Input/output error