Adding a new disk to a VM fails with a SanlockException, 'No space left on device'.

Issue

Creating a new virtual disk is not possible.

2013-Mar-11, 15:13:27 Add-Disk operation of Disk 1 was initiated on VM vm-x by user-x.
2013-Mar-11, 15:13:36 Operation Add-Disk failed to complete on VM vm-x.

The /var/log/vdsm/vdsm.log file contains the following sequence;

b1d7d0d3-f84f-45bf-b4b3-f07ff97ccc93::ERROR::2013-03-11 14:13:29,334::volume::512::Storage.Volume::(create) Unexpected error
Traceback (most recent call last):
  File "/usr/share/vdsm/storage/volume.py", line 506, in create
  File "/usr/share/vdsm/storage/blockVolume.py", line 617, in newVolumeLease
SanlockException: (28, 'Sanlock resource init failure', 'No space left on device')

b1d7d0d3-f84f-45bf-b4b3-f07ff97ccc93::ERROR::2013-03-11 14:13:29,336::task::853::TaskManager.Task::(_setError) Task=`b1d7d0d3-f84f-45bf-b4b3-f07ff97ccc93`::Unexpected error
Traceback (most recent call last):
  File "/usr/share/vdsm/storage/task.py", line 861, in _run
  File "/usr/share/vdsm/storage/task.py", line 320, in run
  File "/usr/share/vdsm/storage/securable.py", line 63, in wrapper
  File "/usr/share/vdsm/storage/sp.py", line 1899, in createVolume
  File "/usr/share/vdsm/storage/blockSD.py", line 612, in createVolume
  File "/usr/share/vdsm/storage/volume.py", line 514, in create
VolumeCreationError: Error creating a new volume: ('Volume creation %s failed: %s', '9dd11bba-bf34-4ead-b3a4-6ccf00831e78', SanlockException(28, 'Sanlock resource init failure', 'No space left on device'))