Pull btrfs updates from David Sterba:
 "Mostly core changes and cleanups, some notable fixes and two
  performance improvements in directory logging.

  The IO path cleanups are removing or refactoring old code, scrub main
  loop has been completely rewritten also refactoring old code.

  There are some changes to non-btrfs code, mostly trivial, the cgroup
  punt bio logic is only moved from generic code.

  Performance improvements:

   - improve logging changes in a directory during one transaction,
     avoid iterating over items and reduce lock contention (fsync time
     4x lower)

   - when logging directory entries during one transaction, reduce
     locking of subvolume trees by checking tree-log instead
     (improvement in throughput and latency for concurrent access to a
     subvolume)

  Notable fixes:

   - dev-replace:
      - properly honor read mode when requested to avoid reading from
        source device
      - target device won't be used for eventual read repair, this is
        unreliable for NODATASUM files
      - when there are unpaired (and unrepairable) metadata during
        replace, exit early with error and don't try to finish whole
        operation

   - scrub ioctl properly rejects unknown flags

   - fix global block reserve calculations

   - fix partial direct io write when there's a page fault in the
     middle, iomap will try to continue with partial request but the
     btrfs part did not match that, this can lead to zeros written
     instead of data

  Core changes:

   - io path:
      - continued cleanups and refactoring around bio handling
      - extent io submit path simplifications and cleanups
      - flush write path simplifications and cleanups
      - rework logic of passing sync mode of bio, with further cleanups

   - rewrite scrub code flow, restructure how the stripes are enumerated
     and verified in a more unified way

   - allow to set lower threshold for block group reclaim in debug mode
     to aid zoned mode testing

   - remove obsolete time-based delayed ref throttling logic when
     truncating items

   - DREW locks are not using percpu variables anymore

   - more warning fixes (-Wmaybe-uninitialized)

   - u64 division simplifications

   - error handling improvements

  Non-btrfs code changes:

   - push cgroup punt bio logic to btrfs code (there was no other user
     of that), the functionality can be now selected separately by
     BLK_CGROUP_PUNT_BIO

   - crc32c_impl removed after removing last uses in btrfs code

   - add btrfs_assertfail() to objtool table"

* tag 'for-6.4-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/kdave/linux: (147 commits)
  btrfs: mark btrfs_assertfail() __noreturn
  btrfs: fix uninitialized variable warnings
  btrfs: use log root when iterating over index keys when logging directory
  btrfs: avoid iterating over all indexes when logging directory
  btrfs: dev-replace: error out if we have unrepaired metadata error during
  btrfs: remove pointless loop at btrfs_get_next_valid_item()
  btrfs: scrub: reject unsupported scrub flags
  btrfs: reinterpret async discard iops_limit=0 as no delay
  btrfs: set default discard iops_limit to 1000
  btrfs: remove unused raid56 functions which were dedicated for scrub
  btrfs: scrub: remove scrub_bio structure
  btrfs: scrub: remove scrub_block and scrub_sector structures
  btrfs: scrub: remove the old scrub recheck code
  btrfs: scrub: remove the old writeback infrastructure
  btrfs: scrub: remove scrub_parity structure
  btrfs: scrub: use scrub_stripe to implement RAID56 P/Q scrub
  btrfs: scrub: switch scrub_simple_mirror() to scrub_stripe infrastructure
  btrfs: scrub: introduce helper to queue a stripe for scrub
  btrfs: scrub: introduce error reporting functionality for scrub_stripe
  btrfs: scrub: introduce a writeback helper for scrub_stripe
  ...