Pull ceph updates from Ilya Dryomov:
 "A varied set of changes:

   - a large rework of cephx auth code to cope with CONFIG_VMAP_STACK
     (myself). Also fixed a deadlock caused by a bogus allocation on the
     writeback path and authorize reply verification.

   - a fix for long stalls during fsync (Jeff Layton). The client now
     has a way to force the MDS log flush, leading to ~100x speedups in
     some synthetic tests.

   - a new [no]require_active_mds mount option (Zheng Yan).

     On mount, we will now check whether any of the MDSes are available
     and bail rather than block if none are. This check can be avoided
     by specifying the "no" option.

   - a couple of MDS cap handling fixes and a few assorted patches
     throughout"

* tag 'ceph-for-4.10-rc1' of git://github.com/ceph/ceph-client: (32 commits)
  libceph: remove now unused finish_request() wrapper
  libceph: always signal completion when done
  ceph: avoid creating orphan object when checking pool permission
  ceph: properly set issue_seq for cap release
  ceph: add flags parameter to send_cap_msg
  ceph: update cap message struct version to 10
  ceph: define new argument structure for send_cap_msg
  ceph: move xattr initialzation before the encoding past the ceph_mds_caps
  ceph: fix minor typo in unsafe_request_wait
  ceph: record truncate size/seq for snap data writeback
  ceph: check availability of mds cluster on mount
  ceph: fix splice read for no Fc capability case
  ceph: try getting buffer capability for readahead/fadvise
  ceph: fix scheduler warning due to nested blocking
  ceph: fix printing wrong return variable in ceph_direct_read_write()
  crush: include mapper.h in mapper.c
  rbd: silence bogus -Wmaybe-uninitialized warning
  libceph: no need to drop con->mutex for ->get_authorizer()
  libceph: drop len argument of *verify_authorizer_reply()
  libceph: verify authorize reply on connect
  ...