[manila] Enabling CephFS snapshot support by default
Hi Zorillas and interested parties,
(Copying a couple of folks explicitly as they may not be part of
Manila's CephFS driver has a configuration option
"cephfs_enable_snapshots" that administrators can toggle in
manila.conf to allow project users to take snapshots of their shares.
 This option has defaulted to False, since the time the CephFS
driver was introduced (Mitaka release of OpenStack Manila)
IIUC, CephFS snapshots have been "stable" since the Mimic release of
CephFS, which debuted in June 2018.  Since then, ceph
deployers/administrators don't have to toggle anything on the backend
to enable snapshots.
So, can we consider changing the default value of the config opt in
manila to "True" in the Train release? This will allow the driver to
report the capability "snapshot_support" as enabled, and makes life
easier for OpenStack deployers/administrators. I would also love to
deprecate this option and remove it in a future release, since it
isn't really necessary, read on:
Users cannot arbitrarily take snapshots in manila, there are a couple
of things that can be used to prevent them: Quotas and Share Types.
Unless users create their shares using a share type that explicitly
requests "snapshot_support", users can't snapshot their shares. So,
we're covered by the service's API in case someone is afraid this has
an impact on someone in the wild using newer versions of Manila with
older versions of Ceph, where snapshots were unstable.