[Qemu-block] qemu-img: Check failed: No space left on device

[Nicolas Ecarnot]

Hello,

First post here, so maybe I should introduce myself :
- I'm a sysadmin for decades and currently managing 4 oVirt clusters, 
made out of tens of hypervisors, all are CentOS 7.2+ based.
- I'm very happy with this solution we choose especially because it is 
based on qemu-kvm (open source, reliable, documented).

On one VM, we experienced the following :
- oVirt/vdsm is detecting an issue on the image
- following this hints https://access.redhat.com/solutions/1173623, I 
managed to detect one error and fix it
- the VM is now running perfectly

On two other VMs, we experienced a similar situation, except the check 
stage is showing something like 14000+ errors, and the relevant logs are :

Repairing refcount block 14 is outside image
ERROR could not resize image: Invalid argument
ERROR cluster 425984 refcount=0 reference=1
ERROR cluster 425985 refcount=0 reference=1
[... repeating the previous line 7000+ times...]
ERROR cluster 457166 refcount=0 reference=1
Rebuilding refcount structure
ERROR writing refblock: No space left on device
qemu-img: Check failed: No space left on device

You surely know that oVirt/RHEV is storing its qcow2 images in dedicated 
logical volumes.

pvs/vgs/lvs are all showing there is plenty of space available, so I 
understand that I don't understand what "No space left on device" means.

The relevant versions are :
- qemu-img-ev-2.3.0-31.el7_2.10.1.x86_64.
- libvirt-daemon-kvm-1.2.17-13.el7_2.4.x86_64
- vdsm-4.17.32-1.el7.noarch
- # qemu-img info /the/relevant/logical/volume/path
file format: qcow2
virtual size: 30G (32212254720 bytes)
disk size: 0
cluster_size: 65536
Format specific information:
    compat: 0.10
    refcount bits: 16

Is there a hope I'll be able to repair this image?

--
Nicolas ECARNOT