Merge tag 'for-6.15-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/kdave/linux

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

   - fall back to buffered write if direct io is done on a file that
     requires checksums
      - this avoids a problem with checksum mismatch errors, observed
        e.g. on virtual images when writes to pages under writeback
        cause the checksum mismatch reports
      - this may lead to some performance degradation but currently the
        recommended setup for VM images is to use the NOCOW file
        attribute that also disables checksums

   - fast/realtime zstd levels -15 to -1
      - supported by mount options (compress=zstd:-5) and defrag ioctl
      - improved speed, reduced compression ratio, check the commit for
        sample measurements

   - defrag ioctl extended to accept negative compression levels

   - subpage mode
      - remove warning when subpage mode is used, the feature is now
        reasonably complete and tested
      - in debug mode allow to create 2K b-tree nodes to allow testing
        subpage on x86_64 with 4K pages too

  Performance improvements:

   - in send, better file path caching improves runtime (on sample load
     by -30%)

   - on s390x with hardware zlib support prepare the input buffer in a
     better way to get the best results from the acceleration

   - minor speed improvement in encoded read, avoid memory allocation in
     synchronous mode

  Core:

   - enable stable writes on inodes, replacing manually waiting for
     writeback and allowing to skip that on inodes without checksums

   - add last checks and warnings for out-of-band dirty writes to pages,
     requiring a fixup ("fixup worker"), this should not be necessary
     since 5.8 where get_user_page() and pin_user_pages*() prevent this
      - long history behind that, we'll be happy to remove the whole
        infrastructure in the near future

   - more folio API conversions and preparations for large folio support

   - subpage cleanups and refactoring, split handling of data and
     metadata to allow future support for large folios

   - readpage works as block-by-block, no change for normal mode, this
     is preparation for future subpage updates

   - block group refcount fixes and hardening

   - delayed iput fixes

   - in zoned mode, fix zone activation on filesystem with missing
     devices

  Cleanups:

   - inode parameter cleanups

   - path auto-freeing updates

   - code flow simplifications in send

   - redundant parameter cleanups"

* tag 'for-6.15-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/kdave/linux: (164 commits)
  btrfs: zoned: fix zone finishing with missing devices
  btrfs: zoned: fix zone activation with missing devices
  btrfs: remove end_no_trans label from btrfs_log_inode_parent()
  btrfs: simplify condition for logging new dentries at btrfs_log_inode_parent()
  btrfs: remove redundant else statement from btrfs_log_inode_parent()
  btrfs: use memcmp_extent_buffer() at replay_one_extent()
  btrfs: update outdated comment for overwrite_item()
  btrfs: use variables to store extent buffer and slot at overwrite_item()
  btrfs: avoid unnecessary memory allocation and copy at overwrite_item()
  btrfs: don't clobber ret in btrfs_validate_super()
  btrfs: prepare btrfs_page_mkwrite() for large folios
  btrfs: prepare extent_io.c for future large folio support
  btrfs: prepare btrfs_launcher_folio() for large folios support
  btrfs: replace PAGE_SIZE with folio_size for subpage.[ch]
  btrfs: add a size parameter to btrfs_alloc_subpage()
  btrfs: subpage: make btrfs_is_subpage() check against a folio
  btrfs: add extra warning if delayed iput is added when it's not allowed
  btrfs: avoid redundant path slot assignment in btrfs_search_forward()
  btrfs: remove unnecessary btrfs_key local variable in btrfs_search_forward()
  btrfs: simplify the return value handling in search_ioctl()
  ...