---
upgrade:
  - |
    The ``default_volume_type`` configuration option is now required
    to have a value.  The default value is ``__DEFAULT__``, so you
    should see no change in behavior whether or not you have set a
    value for ``default_volume_type``.  See
    `Bug #1886632 <https://bugs.launchpad.net/cinder/+bug/1886632>`_
    for more information about this change.

fixes:
  - |
    `Bug #1886632 <https://bugs.launchpad.net/cinder/+bug/1886632>`_:
    The system defined ``__DEFAULT__`` volume type is now treated as
    a regular volume-type and may be updated or deleted.  Since the
    configured ``default_volume_type`` cannot be deleted, however,
    the ``__DEFAULT__`` volume type may not be deleted if it is the
    value of that configuration option.

other:
  - |
    Beginning with the Train release, untyped volumes (that is, volumes with
    no volume-type) have been disallowed.  To facilitate this, a
    ``__DEFAULT__`` volume-type was included as part of the Train database
    migration.  In this release, handling of the default volume-type has been
    improved:

    * The ``default_volume_type`` configuration option is required to have a
      value.  The default value is ``__DEFAULT__``.
    * A request to delete the currently configured ``default_volume_type``
      will fail.  (You can delete that volume-type, but you cannot do it
      while it is the value of the configuration option.)
    * There must always be at least one volume-type defined in a Cinder
      installation.  This is enforced by the type-delete call.
    * If the ``default_volume_type`` is misconfigured (that is, if the value
      refers to a non-existent volume-type), requests that rely on the
      default volume-type (for example, a volume-create request that does
      not specify a volume-type) will result in a HTTP 500 response.