LVMVolumeDriver is missing *_export functions

[glance]

I run a testenviorment of openstack on just one machine, and thus like to use the LVMVolumeDriver to minimize overhead and still use cinder.

The LVMVolumeDriver is missing *_export functions and thus fails on NotImplementedError for some operations.

I currently just hacked lvm.py and added:
"""
    def ensure_export(self, context, volume):
        pass

    def create_export(self, context, volume):
        pass

    def remove_export(self, context, volume):
        pass
"""

And now things work.

[Eric Harney (eharney)]

As noted by pylint:

************* Module cinder.volume.drivers.lvm
W: 58, 0: Method 'initialize_connection' is abstract in class 'VolumeDriver' but is not overridden (abstract-method)
W: 58, 0: Method 'ensure_export' is abstract in class 'VolumeDriver' but is not overridden (abstract-method)
W: 58, 0: Method 'remove_export' is abstract in class 'VolumeDriver' but is not overridden (abstract-method)
W: 58, 0: Method 'create_export' is abstract in class 'VolumeDriver' but is not overridden (abstract-method)
W: 58, 0: Method 'terminate_connection' is abstract in class 'VolumeDriver' but is not overridden (abstract-method)

Interesting use case as I haven't heard of anyone using LVMVolumeDriver like this directly, but it seems like a simple enough thing to fix up and may be handy for testing.

[Eric Harney (eharney)]

Another approach here may be to use iscsi_helper = 'fake' and the LVMISCSIDriver.

If that works then we should just implement something that yells if someone tries to use LVMVolumeDriver as the actual volume driver rather than ISCSI/ISER.

[zhangyu (raliny0903)]

if you set iscsi_helper = 'fake' and the LVMISCSIDriver,you can create a cinder volume.but when you want to attach the volume to a instance,that maybe failed ,because you didn't create a iscsi target.

[Saggi Mizrahi (ficoos)]

Looking at the code the methods are clearly there in lvm.py