Description of problem:
First use qemu-img create a qcow2 img file, size as 4G. then use virt-manager to install a guest, select this qcow2 img as storage, found that disk size=0, which makes installation fail.

Version-Release number of selected component (if applicable):
# uname -a
Linux localhost.localdomain 2.6.18-237.el5 #1 SMP Mon Dec 13 18:07:57 EST 2010 x86_64 x86_64 x86_64 GNU/Linux
kvm-83-224.el5
libvirt-0.8.2-15.el5

How reproducible:
Always

Steps to Reproduce:
1. Prepare a qcow2 img file
# qemu-img create -f qcow2 qcow2-test 4G
Formatting 'qcow2-test', fmt=qcow2, size=4194304 kB

# qemu-img info qcow2-test 
image: qcow2-test
file format: qcow2
virtual size: 4.0G (4294967296 bytes)
disk size: 144K
cluster_size: 65536
  
2. Use virt-manager to install a new guest, select qcow2-test as disk img storage. prepare to install, then found 0MB disk size for this img, and make installation fail.

3. # ll -lhs /var/lib/libvirt/images
144K -rw-r--r-- 1 root root 256K Mar 21 21:52 qcow2-test

Actual results:
Installation fails because disk img file size is 0.

Expected results:
Disk size should be 4GB

Additional info:

I can reproduce this bug with RHEL5.6.z, libvirt-0.8.2-15.el5_6.3.

And it works well in RHEL6.1,libvirt-0.8.7-13.el6.