Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
  new helper: mount_subtree()
  switch create_mnt_ns() to saner calling conventions, fix double mntput() in nfs
  btrfs: fix double mntput() in mount_subvol()