Pull btrfs updates from David Sterba:
 "User visible features:

   - added support for the ioctl FS_IOC_FSGETXATTR, per-inode flags,
     successor of GET/SETFLAGS; now supports only existing flags:
     append, immutable, noatime, nodump, sync

   - 3 new unprivileged ioctls to allow users to enumerate subvolumes

   - dedupe syscall implementation does not restrict the range to 16MiB,
     though it still splits the whole range to 16MiB chunks

   - on user demand, rmdir() is able to delete an empty subvolume,
     export the capability in sysfs

   - fix inode number types in tracepoints, other cleanups

   - send: improved speed when dealing with a large removed directory,
     measurements show decrease from 2000 minutes to 2 minutes on a
     directory with 2 million entries

   - pre-commit check of superblock to detect a mysterious in-memory
     corruption

   - log message updates

  Other changes:

   - orphan inode cleanup improved, does no keep long-standing
     reservations that could lead up to early ENOSPC in some cases

   - slight improvement of handling snapshotted NOCOW files by avoiding
     some unnecessary tree searches

   - avoid OOM when dealing with many unmergeable small extents at flush
     time

   - speedup conversion of free space tree representations from/to
     bitmap/tree

   - code refactoring, deletion, cleanups:
      + delayed refs
      + delayed iput
      + redundant argument removals
      + memory barrier cleanups
      + remove a redundant mutex supposedly excluding several ioctls to
        run in parallel

   - new tracepoints for blockgroup manipulation

   - more sanity checks of compressed headers"

* tag 'for-4.18-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/kdave/linux: (183 commits)
  btrfs: Add unprivileged version of ino_lookup ioctl
  btrfs: Add unprivileged ioctl which returns subvolume's ROOT_REF
  btrfs: Add unprivileged ioctl which returns subvolume information
  Btrfs: clean up error handling in btrfs_truncate()
  btrfs: Factor out write portion of btrfs_get_blocks_direct
  btrfs: Factor out read portion of btrfs_get_blocks_direct
  btrfs: return ENOMEM if path allocation fails in btrfs_cross_ref_exist
  btrfs: raid56: Remove VLA usage
  btrfs: return error value if create_io_em failed in cow_file_range
  btrfs: drop useless member qgroup_reserved of btrfs_pending_snapshot
  btrfs: drop unused parameter qgroup_reserved
  btrfs: balance dirty metadata pages in btrfs_finish_ordered_io
  btrfs: lift some btrfs_cross_ref_exist checks in nocow path
  btrfs: Remove fs_info argument from btrfs_uuid_tree_rem
  btrfs: Remove fs_info argument from btrfs_uuid_tree_add
  Btrfs: remove unused check of skip_locking
  Btrfs: remove always true check in unlock_up
  Btrfs: grab write lock directly if write_lock_level is the max level
  Btrfs: move get root out of btrfs_search_slot to a helper
  Btrfs: use more straightforward extent_buffer_uptodate check
  ...