Merge tag 'for-5.1-part1-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/kdave...

Pull btrfs updates from David Sterba:
 "This contains usual mix of new features, core changes and fixes; full
  list below. I'm planning second pull request, with a few more fixes
  that arrived recently but too close to merge window, will send it next
  week.

  New features:

   - support zstd compression levels

   - new ioctl to unregister a device from the module (ie. reverse of
     device scan)

   - scrub prints a message to log when it's about to start or finish

  Core changes:

   - qgroups can now skip part of a tree that does not get updated
     during relocation, because this does not affect the quota
     accounting, estimated speedup in run time is about 20%

   - the compression workspace management had to be enhanced due to zstd
     requirements

   - various enospc fixes, when there's high fragmentation the
     over-reservation can cause ENOSPC that might not happen after a
     flush, in such cases try to wait if the situation improves

  Fixes:

   - various ioctls could overwrite previous return value if
     copy_to_user fails, fix this so the original error is reported

   - more reclaim vs GFP_KERNEL fixes

   - other cleanups and refactoring

   - fix a (valid) lockdep warning in a test when device replace is
     destroying worker threads

   - make qgroup async transaction commit more aggressive, this avoids
     some 'quota limit reached' errors if there are not enough data to
     trigger transaction in order to flush

   - fix deadlock between snapshot deletion and quotas when backref
     walking is called from context that already holds the same locks

   - fsync fixes:
      - fix fsync after succession of renames of different files
      - fix fsync after succession of renames and unlink/rmdir"

* tag 'for-5.1-part1-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/kdave/linux: (92 commits)
  btrfs: Remove unnecessary casts in btrfs_read_root_item
  Btrfs: remove assertion when searching for a key in a node/leaf
  Btrfs: add missing error handling after doing leaf/node binary search
  btrfs: drop the lock on error in btrfs_dev_replace_cancel
  btrfs: ensure that a DUP or RAID1 block group has exactly two stripes
  btrfs: init csum_list before possible free
  Btrfs: remove no longer needed range length checks for deduplication
  Btrfs: fix fsync after succession of renames and unlink/rmdir
  Btrfs: fix fsync after succession of renames of different files
  btrfs: honor path->skip_locking in backref code
  btrfs: qgroup: Make qgroup async transaction commit more aggressive
  btrfs: qgroup: Move reserved data accounting from btrfs_delayed_ref_head to btrfs_qgroup_extent_record
  btrfs: scrub: remove unused nocow worker pointer
  btrfs: scrub: add assertions for worker pointers
  btrfs: scrub: convert scrub_workers_refcnt to refcount_t
  btrfs: scrub: add scrub_lock lockdep check in scrub_workers_get
  btrfs: scrub: fix circular locking dependency warning
  btrfs: fix comment its device list mutex not volume lock
  btrfs: extent_io: Kill the forward declaration of flush_write_bio
  btrfs: Fix grossly misleading argument names in extent io search
  ...