Comment 0 for bug 1741476

The introduction of "new style volume attachments" seems to have caused a regression, breaking read-only volume attachments.

Trace: http://paste.openstack.org/raw/639097/

The reason seems to be the fact that Cinder expects the connector provided through the "attachment_update" call to include the requested attach mode [1], otherwise assuming it to be 'rw'. As Nova won't provide it, Cinder will then error because of an access mode mismatch.

[1] https://github.com/openstack/cinder/blob/d96b6dfba03424baf8b3ddc7539347554892e941/cinder/volume/manager.py#L4374-L4393