The big ticket item here is support for rbd exclusive-lock feature,

with maintenance operations offloaded to userspace (Douglas Fuller,
 Mike Christie and myself).  Another block device bullet is a series
 fixing up layering error paths (myself).
 
 On the filesystem side, we've got patches that improve our handling of
 buffered vs dio write races (Neil Brown) and a few assorted fixes from
 Zheng.  Also included a couple of random cleanups and a minor CRUSH
 update.
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Merge tag 'ceph-for-4.9-rc1' of git://github.com/ceph/ceph-client

Pull Ceph updates from Ilya Dryomov:
 "The big ticket item here is support for rbd exclusive-lock feature,
  with maintenance operations offloaded to userspace (Douglas Fuller,
  Mike Christie and myself). Another block device bullet is a series
  fixing up layering error paths (myself).

  On the filesystem side, we've got patches that improve our handling of
  buffered vs dio write races (Neil Brown) and a few assorted fixes from
  Zheng. Also included a couple of random cleanups and a minor CRUSH
  update"

* tag 'ceph-for-4.9-rc1' of git://github.com/ceph/ceph-client: (39 commits)
  crush: remove redundant local variable
  crush: don't normalize input of crush_ln iteratively
  libceph: ceph_build_auth() doesn't need ceph_auth_build_hello()
  libceph: use CEPH_AUTH_UNKNOWN in ceph_auth_build_hello()
  ceph: fix description for rsize and rasize mount options
  rbd: use kmalloc_array() in rbd_header_from_disk()
  ceph: use list_move instead of list_del/list_add
  ceph: handle CEPH_SESSION_REJECT message
  ceph: avoid accessing / when mounting a subpath
  ceph: fix mandatory flock check
  ceph: remove warning when ceph_releasepage() is called on dirty page
  ceph: ignore error from invalidate_inode_pages2_range() in direct write
  ceph: fix error handling of start_read()
  rbd: add rbd_obj_request_error() helper
  rbd: img_data requests don't own their page array
  rbd: don't call rbd_osd_req_format_read() for !img_data requests
  rbd: rework rbd_img_obj_exists_submit() error paths
  rbd: don't crash or leak on errors in rbd_img_obj_parent_read_full_callback()
  rbd: move bumping img_request refcount into rbd_obj_request_submit()
  rbd: mark the original request as done if stat request fails
  ...

Documentation/ABI/testing/sysfs-bus-rbd

@@ -6,7 +6,7 @@ Description:
 
 Being used for adding and removing rbd block devices.
 
-Usage: <mon ip addr> <options> <pool name> <rbd image name> [snap name]
+Usage: <mon ip addr> <options> <pool name> <rbd image name> [<snap name>]
 
  $ echo "192.168.0.1 name=admin rbd foo" > /sys/bus/rbd/add
 
@@ -14,9 +14,13 @@ The snapshot name can be "-" or omitted to map the image read/write. A <dev-id>
 will be assigned for any registered block device. If snapshot is used, it will
 be mapped read-only.
 
-Removal of a device:
+Usage: <dev-id> [force]
 
-  $ echo <dev-id> > /sys/bus/rbd/remove
+ $ echo 2 > /sys/bus/rbd/remove
+
+Optional "force" argument which when passed will wait for running requests and
+then unmap the image. Requests sent to the driver after initiating the removal
+will be failed.  (August 2016, since 4.9.)
 
 What:		/sys/bus/rbd/add_single_major
 Date:		December 2013
@@ -43,10 +47,25 @@ Description:	Available only if rbd module is inserted with single_major
 Entries under /sys/bus/rbd/devices/<dev-id>/
 --------------------------------------------
 
+client_addr
+
+	The ceph unique client entity_addr_t (address + nonce).
+	The format is <address>:<port>/<nonce>: '1.2.3.4:1234/5678' or
+	'[1:2:3:4:5:6:7:8]:1234/5678'.  (August 2016, since 4.9.)
+
 client_id
 
 	The ceph unique client id that was assigned for this specific session.
 
+cluster_fsid
+
+	The ceph cluster UUID.  (August 2016, since 4.9.)
+
+config_info
+
+	The string written into /sys/bus/rbd/add{,_single_major}.  (August
+	2016, since 4.9.)
+
 features
 
 	A hexadecimal encoding of the feature bits for this image.
@@ -92,6 +111,10 @@ current_snap
 
 	The current snapshot for which the device is mapped.
 
+snap_id
+
+	The current snapshot's id.  (August 2016, since 4.9.)
+
 parent
 
 	Information identifying the chain of parent images in a layered rbd