Description of problem:
put image in nfs, start guest, and run dd in guest, then stop nfs. "bdrv_write ret=-5 qcow2: free_clusters failed: Input/output error" is display on monitor

Version-Release number of selected component (if applicable):
kvm-83-164.el5_5.11

How reproducible:
100%

Steps to Reproduce:
1. mount nfs
mount -o rw,soft,timeo=1,retrans=1 10.66.91.146:/root/share /mnt/
2. boot guest
/usr/libexec/qemu-kvm -no-hpet -usbdevice tablet -rtc-td-hack -drive file=/mnt/bak/rhel5.5-64-virtio.qcow2,format=qcow2,media=disk,if=virtio,boot=on,cache=off,index=0,werror=stop -smp 2 -m 2G  -vnc :3 -monitor stdio -net nic,vlan=0,macaddr=20:20:28:99:01:19,model=virtio -net tap,vlan=0,script=//usr/local/staf/test/RHEV/kvm-new/autotest/client/tests/kvm/scripts/qemu-ifup-switch -uuid `uuidgen` -cpu qemu64
3. run  dd
dd if=/dev/zero of=file bs=1M count=100
4. stop nfs

  
Actual results:
"bdrv_write ret=-5"
is display in monitor, can not operate monitor


Expected results:


Additional info: