cephfs: allow prohibiting user snapshots in CephFS
Since snapshots can be used to circumvent (accidentally or not) the quotas as snapshot file data that has since been modified or deleted does not count towards the quota.
(This may already be implemented?)
Alternatively, we could also just start counting the snapshot data but this seems non-trivial?
#4 Updated by Greg Farnum over 4 years ago
We should actually discuss what kind of interface admins want. Dan van der Ster certainly has thoughts; others might as well.
eg an "fs set" max uid is better than nothing, but they might prefer it be set for subtrees similarly to layouts? So a privileged user can grant permission to an unprivileged user to snapshot their directory on a case-by-case basis or something.
#6 Updated by Dan van der Ster over 4 years ago
change default of mds_snap_max_uid to 0
Use-cases such as Manila let the users mount with root so this will be ineffective.
My humble opinion about this topic is to document the behaviour (limitation) until incremental snapshot usage can be accounted properly by the quota.
We can document that "quota" refers to space used by current head, and e.g. "snapquota" is a snapshot aware quota still to be developed...