Pull UBI/UBIFS updates from Richard Weinberger:
 "This pull request contains:

   - Fixes for both UBI and UBIFS
   - overlayfs support (O_TMPFILE, RENAME_WHITEOUT/EXCHANGE)
   - Code refactoring for the upcoming MLC support"

[ Ugh, we just got rid of the "rename2()" naming for the extended rename
  functionality. And this re-introduces it in ubifs with the cross-
  renaming and whiteout support.

  But rather than do any re-organizations in the merge itself, the
  naming can be cleaned up later ]

* tag 'upstream-4.9-rc1' of git://git.infradead.org/linux-ubifs: (27 commits)
  UBIFS: improve function-level documentation
  ubifs: fix host xattr_len when changing xattr
  ubifs: Use move variable in ubifs_rename()
  ubifs: Implement RENAME_EXCHANGE
  ubifs: Implement RENAME_WHITEOUT
  ubifs: Implement O_TMPFILE
  ubi: Fix Fastmap's update_vol()
  ubi: Fix races around ubi_refill_pools()
  ubi: Deal with interrupted erasures in WL
  UBI: introduce the VID buffer concept
  UBI: hide EBA internals
  UBI: provide an helper to query LEB information
  UBI: provide an helper to check whether a LEB is mapped or not
  UBI: add an helper to check lnum validity
  UBI: simplify LEB write and atomic LEB change code
  UBI: simplify recover_peb() code
  UBI: move the global ech and vidh variables into struct ubi_attach_info
  UBI: provide helpers to allocate and free aeb elements
  UBI: fastmap: use ubi_io_{read, write}_data() instead of ubi_io_{read, write}()
  UBI: fastmap: use ubi_rb_for_each_entry() in unmap_peb()
  ...