Description of problem:

Fail to do external disk-only snapshot when guest use FC storage

Version-Release number of selected component (if applicable):

libvirt-0.10.2-33.el6.x86_64
qemu-kvm-rhev-0.12.1.2-2.424.el6.x86_64


How reproducible:

100%

Steps to Reproduce:


1.define an mpath type pool on host with FC storage

# virsh pool-dumpxml mpath
<pool type='mpath'>
  <name>mpath</name>
  <uuid>a758ca5b-3b4b-1f01-9fb6-bbd39e4180f7</uuid>
  <capacity unit='bytes'>21481278464</capacity>
  <allocation unit='bytes'>21481278464</allocation>
  <available unit='bytes'>0</available>
  <source>
  </source>
  <target>
    <path>/dev/mapper</path>
    <permissions>
      <mode>0755</mode>
      <owner>-1</owner>
      <group>-1</group>
    </permissions>
  </target>
</pool>

# virsh vol-list mpath
Name                 Path                                    
-----------------------------------------
dm-0                 /dev/mapper/mpatha    

Create a guest storage in fc storage

# qemu-img create -f qcow2 /dev/mapper/mpatha 100G

# qemu-img info /dev/mapper/mpatha
image: /dev/mapper/mpatha
file format: qcow2
virtual size: 100G (107374182400 bytes)
disk size: 0
cluster_size: 65536

2.define a guest with storage created in step1, install an rhel6.5 OS on guest.
# virsh dumpxml test  |grep disk -A 3
    <disk type='block' device='disk'>
      <driver name='qemu' type='qcow2' cache='none' io='native'/>
      <source dev='/dev/mapper/mpatha'/>
      <target dev='vda' bus='virtio'/>
      <alias name='virtio-disk0'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x06' function='0x0'/>
    </disk>

3.after guest os boot up, create external disk-only snapshot
# virsh snapshot-create-as test s1 --disk-only --diskspec vda,file=/tmp/s1.img
error: internal error unable to execute QEMU command 'transaction': Could not open '/dev/mapper/mpatha': Permission denied

4. do external disk-only snapshot when guest is booting up

# virsh destroy test;virsh start test;virsh snapshot-create-as test s1 --disk-only --diskspec vda,file=/tmp/s1.img
Domain test destroyed

Domain test started

5. check the snapshot info

# virsh snapshot-current test
<domainsnapshot>
  <name>s1</name>
  <state>disk-snapshot</state>
  <creationTime>1397734325</creationTime>
  <memory snapshot='no'/>
  <disks>
    <disk name='vda' snapshot='external'>
      <driver type='qcow2'/>
      <source file='/tmp/s1.img'/>
    </disk>
  </disks>
  <domain type='kvm'>
..

# virsh snapshot-info test s1 
Name:           s1
Domain:         test
Current:        yes
State:          disk-snapshot
Location:       external
Parent:         -
Children:       0
Descendants:    0
Metadata:       yes


Domain snapshot s1 created


Actual results:


Expected results:

should succeed creating external disk-only snapshot when guest is running.

Additional info:


error in log:
2014-04-17 08:30:24.826+0000: 17958: error : qemuMonitorJSONCheckError:357 : internal error unable to execute QEMU command 'transaction': Could not open '/dev/mapper/mpatha': Permission denied