ensure_export model_update ignored

[Walt Boring]

The volume manager calls the driver's ensure_export() at startup time. There are several volume drivers that return a model_update from ensure_export, but the volume driver ignores that model_update.

https://github.com/openstack/cinder/blob/master/cinder/volume/manager.py#L553

For example,

cinder reference driver lvm.py
https://github.com/openstack/cinder/blob/master/cinder/volume/drivers/lvm.py#L816-L824

hpe 3par driver
https://github.com/openstack/cinder/blob/master/cinder/volume/drivers/hpe/hpe_3par_iscsi.py#L754-L783

https://github.com/openstack/cinder/blob/master/cinder/volume/drivers/linstordrv.py#L1052-L1058

[Eric Harney (eharney)]

In the case of the LVM driver, this doesn't seem to matter, because it returns ensure_export() from the target driver, but none of the target drivers appear to return anything.

Does the 3par driver actually return updated values in this situation? Do any other drivers?

I ask because it's not clear if we actually need to apply model_updates from the ensure_export driver method -- the API may just be that it isn't expected to update any information.

[Brian Rosmaita (brian-rosmaita)]

We should discuss this at the PTG. Looking at the "interface methods for data path" part of the code, https://github.com/openstack/cinder/blob/master/cinder/volume/driver.py#L1428 , some methods are explicitly documented that they can optionally return a dict, but ensure_export is not.