13.0.0
------

* The RBD C API's rbd_discard method now enforces a maximum length of
  2GB to match the C++ API's Image::discard method. This restriction
  prevents overflow of the result code.

* *CephFS*:

  * Several "ceph mds" commands have been obsoleted and replaced
    by equivalent "ceph fs" commands:
      - mds dump -> fs dump
      - mds getmap -> fs dump
      - mds stop -> mds deactivate
      - mds set_max_mds -> fs set max_mds
      - mds set -> fs set
      - mds cluster_down -> fs set cluster_down true
      - mds cluster_up -> fs set cluster_down false
      - mds add_data_pool -> fs add_data_pool
      - mds remove_data_pool -> fs rm_data_pool
      - mds rm_data_pool -> fs rm_data_pool

  * New CephFS file system attributes session_timeout and session_autoclose
    are configurable via `ceph fs set`. The MDS config options
    mds_session_timeout, mds_session_autoclose, and mds_max_file_size are now
    obsolete.

  * The JSON format of `ceph fs status` and `ceph mds stat` has changed
    for the "up" and "info" sections of the mds_map.

>= 12.2.2
---------

- *CephFS*:

  * The CephFS client now catches failures to clear dentries during startup
    and refuses to start as consistency and untrimmable cache issues may
    develop. The new option client_die_on_failed_dentry_invalidate (default:
    true) may be turned off to allow the client to proceed (dangerous!).