Pull btrfs updates from David Sterba:
 "This continues with work on code refactoring, sanity checks and space
  handling. There are some less user visible changes, nothing that would
  particularly stand out.

  User visible changes:
   - tree checker, more sanity checks of:
       - ROOT_ITEM (key, size, generation, level, alignment, flags)
       - EXTENT_ITEM and METADATA_ITEM checks (key, size, offset,
         alignment, refs)
       - tree block reference items
       - EXTENT_DATA_REF (key, hash, offset)

   - deprecate flag BTRFS_SUBVOL_CREATE_ASYNC for subvolume creation
     ioctl, scheduled removal in 5.7

   - delete stale and unused UAPI definitions
     BTRFS_DEV_REPLACE_ITEM_STATE_*

   - improved export of debugging information available via existing
     sysfs directory structure

   - try harder to delete relations between qgroups and allow to delete
     orphan entries

   - remove unreliable space checks before relocation starts

  Core:
   - space handling:
       - improved ticket reservations and other high level logic in
         order to remove special cases
       - factor flushing infrastructure and use it for different
         contexts, allows to remove some special case handling
       - reduce metadata reservation when only updating inodes
       - reduce global block reserve minimum size (affects small
         filesystems)
       - improved overcommit logic wrt global block reserve

   - tests:
       - fix memory leaks in extent IO tree
       - catch all TRIM range

  Fixes:
   - fix ENOSPC errors, leading to transaction aborts, when cloning
     extents

   - several fixes for inode number cache (mount option inode_cache)

   - fix potential soft lockups during send when traversing large trees

   - fix unaligned access to space cache pages with SLUB debug on
     (PowerPC)

  Other:
   - refactoring public/private functions, moving to new or more
     appropriate files

   - defines converted to enums

   - error handling improvements

   - more assertions and comments

   - old code deletion"

* tag 'for-5.4-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/kdave/linux: (138 commits)
  btrfs: Relinquish CPUs in btrfs_compare_trees
  btrfs: Don't assign retval of btrfs_try_tree_write_lock/btrfs_tree_read_lock_atomic
  btrfs: create structure to encode checksum type and length
  btrfs: turn checksum type define into an enum
  btrfs: add enospc debug messages for ticket failure
  btrfs: do not account global reserve in can_overcommit
  btrfs: use btrfs_try_granting_tickets in update_global_rsv
  btrfs: always reserve our entire size for the global reserve
  btrfs: change the minimum global reserve size
  btrfs: rename btrfs_space_info_add_old_bytes
  btrfs: remove orig_bytes from reserve_ticket
  btrfs: fix may_commit_transaction to deal with no partial filling
  btrfs: rework wake_all_tickets
  btrfs: refactor the ticket wakeup code
  btrfs: stop partially refilling tickets when releasing space
  btrfs: add space reservation tracepoint for reserved bytes
  btrfs: roll tracepoint into btrfs_space_info_update helper
  btrfs: do not allow reservations if we have pending tickets
  btrfs: stop clearing EXTENT_DIRTY in inode I/O tree
  btrfs: treat RWF_{,D}SYNC writes as sync for CRCs
  ...