Description:
The guest image has a backing file on shared nfs server. (Don't pre-create image on target host.) After migration with --copy-storage-inc, the backing file info is missing on target host. And the guest restart failed with following error:
Booting from Hard Disk...
Boot failed: not a bootable disk
No bootable device


Version:
libvirt-1.2.17-3.el7.x86_64
qemu-kvm-rhev-2.3.0-13.el7.x86_64

How reproducible:
100%

Steps to Reproduce:
0.Prepare two hosts: source(RHEL7.2) and target(RHEL7.2)

1.Prepare an image with a guest installed with qcow2 type and put it in shared nfs.

2.Create an image based on the above image on source host:

# qemu-img create /var/lib/libvirt/images/mig2inc.qcow2 -f qcow2 -b /90121/fjin/r71-3.qcow2
Formatting '/var/lib/libvirt/images/mig2inc.qcow2', fmt=qcow2 size=9663676416 backing_file='/90121/fjin/r71-3.qcow2' encryption=off cluster_size=65536 lazy_refcounts=off refcount_bits=16

# qemu-img info /var/lib/libvirt/images/mig2inc.qcow2
image: /var/lib/libvirt/images/mig2inc.qcow2
file format: qcow2
virtual size: 9.0G (9663676416 bytes)
disk size: 21M
cluster_size: 65536
backing file: /90121/fjin/r71-3.qcow2
Format specific information:
    compat: 1.1
    lazy refcounts: false
    refcount bits: 16
    corrupt: false

3.Start a guest with image "/var/lib/libvirt/images/mig2inc.qcow2" on source host.
# virsh start mig2
Domain mig2 started

4.Migrate the guest to target host(Note: don't pre-create storage on target):
# virsh migrate --verbose --live --persistent mig2 qemu+ssh://10.66.6.6/system --copy-storage-inc
Migration: [100 %]


5.Check the image info of the guest on target host:

# qemu-img info /var/lib/libvirt/images/mig2inc.qcow2
image: /var/lib/libvirt/images/mig2inc.qcow2
file format: qcow2
virtual size: 9.0G (9663676416 bytes)
disk size: 22M
cluster_size: 65536
Format specific information:
    compat: 0.10
    refcount bits: 16

Compared with the image info on source host, to find that backing file info is missing.

6.Destroy the guest and restart on target host:
# virsh destroy mig2
Domain mig2 destroyed

# virsh start mig2
Domain mig2 started

Guest start failed with the following error:

Booting from Hard Disk...
Boot failed: not a bootable disk
No bootable device

Actual results:
As step 5~6.

Expected results:
The "backing file" info can be preserved after migration.

Additional info:
"copy-storage-all" doesn't have such issue.