doc: v12.1.0 major changes for release

Adding a section for major changes in 12.1.0 release, sorted by sections
so that we can have a consolidated announce when announcing the release

Signed-off-by: Abhishek Lekshmanan <abhishek@suse.com>

doc/release-notes.rst

@@ -2,6 +2,112 @@
  Release Notes
 ===============
 
+v12.1.0 Luminous (RC)
+====================
+
+This is the  first release candidate for Luminous, the next long term stable release.
+
+Major Changes from Kraken
+-------------------------
+
+* When assigning a network to the public network and not to
+  the cluster network the network specification of the public
+  network will be used for the cluster network as well.
+  In older versions this would lead to cluster services
+  being bound to 0.0.0.0:<port>, thus making the
+  cluster service even more publicly available than the
+  public services. When only specifying a cluster network it
+  will still result in the public services binding to 0.0.0.0.
+
+* In previous versions, if a client sent an op to the wrong OSD, the OSD
+  would reply with ENXIO.  The rationale here is that the client or OSD is
+  clearly buggy and we want to surface the error as clearly as possible.
+  We now only send the ENXIO reply if the osd_enxio_on_misdirected_op option
+  is enabled (it's off by default).  This means that a VM using librbd that
+  previously would have gotten an EIO and gone read-only will now see a
+  blocked/hung IO instead.
+
+* The "journaler allow split entries" config setting has been removed.
+
+- *librados*:
+
+  * Some variants of the omap_get_keys and omap_get_vals librados
+    functions have been deprecated in favor of omap_get_vals2 and
+    omap_get_keys2.  The new methods include an output argument
+    indicating whether there are additional keys left to fetch.
+    Previously this had to be inferred from the requested key count vs
+    the number of keys returned, but this breaks with new OSD-side
+    limits on the number of keys or bytes that can be returned by a
+    single omap request.  These limits were introduced by kraken but
+    are effectively disabled by default (by setting a very large limit
+    of 1 GB) because users of the newly deprecated interface cannot
+    tell whether they should fetch more keys or not.  In the case of
+    the standalone calls in the C++ interface
+    (IoCtx::get_omap_{keys,vals}), librados has been updated to loop on
+    the client side to provide a correct result via multiple calls to
+    the OSD.  In the case of the methods used for building
+    multi-operation transactions, however, client-side looping is not
+    practical, and the methods have been deprecated.  Note that use of
+    either the IoCtx methods on older librados versions or the
+    deprecated methods on any version of librados will lead to
+    incomplete results if/when the new OSD limits are enabled.
+
+  * The original librados rados_objects_list_open (C) and objects_begin
+    (C++) object listing API, deprecated in Hammer, has finally been
+    removed.  Users of this interface must update their software to use
+    either the rados_nobjects_list_open (C) and nobjects_begin (C++) API or
+    the new rados_object_list_begin (C) and object_list_begin (C++) API
+    before updating the client-side librados library to Luminous.
+    Object enumeration (via any API) with the latest librados version
+    and pre-Hammer OSDs is no longer supported.  Note that no in-tree
+    Ceph services rely on object enumeration via the deprecated APIs, so
+    only external librados users might be affected.
+
+    The newest (and recommended) rados_object_list_begin (C) and
+    object_list_begin (C++) API is only usable on clusters with the
+    SORTBITWISE flag enabled (Jewel and later).  (Note that this flag is
+    required to be set before upgrading beyond Jewel.)
+
+- *CephFS*:
+
+  * When configuring ceph-fuse mounts in /etc/fstab, a new syntax is
+    available that uses "ceph.<arg>=<val>" in the options column, instead
+    of putting configuration in the device column.  The old style syntax
+    still works.  See the documentation page "Mount CephFS in your
+    file systems table" for details.
+
+  * CephFS clients without the 'p' flag in their authentication capability
+    string will no longer be able to set quotas or any layout fields.  This
+    flag previously only restricted modification of the pool and namespace
+    fields in layouts.
+  * CephFS directory fragmentation (large directory support) is enabled
+    by default on new filesystems.  To enable it on existing filesystems
+    use "ceph fs set <fs_name> allow_dirfrags".
+  * CephFS will generate a health warning if you have fewer standby daemons
+    than it thinks you wanted.  By default this will be 1 if you ever had
+    a standby, and 0 if you did not.  You can customize this using
+    ``ceph fs set <fs> standby_count_wanted <number>``.  Setting it
+    to zero will effectively disable the health check.
+  * The "ceph mds tell ..." command has been removed.  It is superceded
+    by "ceph tell mds.<id> ..."
+
+- *MGR*
+  * ceph-mgr supports a default dashboard
+  * ceph-mgr introduces a new pecan based rest API
+
+- *RGW*:
+
+  * RGW introduces server side encryption of uploaded objects with 3 options for
+    the management of encryption keys, automatic encryption (only recommended for
+    test setups), customer provided keys similar to Amazon SSE-C specification and
+    using a key management service (Openstack Barbician) similar to Amazon SSE-KMS
+    specification.
+  * RGW's metadata search with ElasticSearch now supports end user requests
+    serviced via RGW itself and now supports custom metadata fields
+  * RGW has consolidated the several metadata index pools via the use of rados
+    namespaces
+  * RGW now supports dynamic bucket index sharding
+
 v12.0.3 Luminous (dev)
 ======================