Pull Ceph updates from Ilya Dryomov:
 "The highlights are:

   - RADOS namespace support in libceph and CephFS (Zheng Yan and
     myself).  The stopgaps added in 4.5 to deny access to inodes in
     namespaces are removed and CEPH_FEATURE_FS_FILE_LAYOUT_V2 feature
     bit is now fully supported

   - A large rework of the MDS cap flushing code (Zheng Yan)

   - Handle some of ->d_revalidate() in RCU mode (Jeff Layton).  We were
     overly pessimistic before, bailing at the first sight of LOOKUP_RCU

  On top of that we've got a few CephFS bug fixes, a couple of cleanups
  and Arnd's workaround for a weird genksyms issue"

* tag 'ceph-for-4.8-rc1' of git://github.com/ceph/ceph-client: (34 commits)
  ceph: fix symbol versioning for ceph_monc_do_statfs
  ceph: Correctly return NXIO errors from ceph_llseek
  ceph: Mark the file cache as unreclaimable
  ceph: optimize cap flush waiting
  ceph: cleanup ceph_flush_snaps()
  ceph: kick cap flushes before sending other cap message
  ceph: introduce an inode flag to indicates if snapflush is needed
  ceph: avoid sending duplicated cap flush message
  ceph: unify cap flush and snapcap flush
  ceph: use list instead of rbtree to track cap flushes
  ceph: update types of some local varibles
  ceph: include 'follows' of pending snapflush in cap reconnect message
  ceph: update cap reconnect message to version 3
  ceph: mount non-default filesystem by name
  libceph: fsmap.user subscription support
  ceph: handle LOOKUP_RCU in ceph_d_revalidate
  ceph: allow dentry_lease_is_valid to work under RCU walk
  ceph: clear d_fsinfo pointer under d_lock
  ceph: remove ceph_mdsc_lease_release
  ceph: don't use ->d_time
  ...