Remap tree

This is version 4 of the patch series for the new logical remapping tree
feature - see the previous cover letters for more information including
the rationale:

* RFC: https://lore.kernel.org/all/20250515163641.3449017-1-maha...
* Version 1: https://lore.kernel.org/all/20250605162345.2561026-1-maha...
* Version 2: https://lore.kernel.org/all/20250813143509.31073-1-mark@h...
* Version 3: https://lore.kernel.org/all/20251009112814.13942-1-mark@h...

Changes since version 3:
* Removed search_commit_root code for now
* In-memory free-space tree gets cleared for newly remapped block groups
  when on-disk version does
* Made it so that btrfs_mark_bg_fully_remapped() can't run twice on same
  block group
* Removed now-superfluous divide-by-zero check
* Used block group spinlock to protect remap fields
* Fixed async discard looping over empty block group
* Fixed redundant remap_bytes == 0 checks on remapped block group
* Fixed async discard not throttling correctly for remapped block groups
* Added block_group_is_empty() helper function
* Removed patch "btrfs: release BG lock before calling btrfs_link_bg_list()",
  now not needed

Mark Harmstone (16):
  btrfs: add definitions and constants for remap-tree
  btrfs: add REMAP chunk type
  btrfs: allow remapped chunks to have zero stripes
  btrfs: remove remapped block groups from the free-space tree
  btrfs: don't add metadata items for the remap tree to the extent tree
  btrfs: add extended version of struct block_group_item
  btrfs: allow mounting filesystems with remap-tree incompat flag
  btrfs: redirect I/O for remapped block groups
  btrfs: handle deletions from remapped block group
  btrfs: handle setting up relocation of block group with remap-tree
  btrfs: move existing remaps before relocating block group
  btrfs: replace identity remaps with actual remaps when doing
    relocations
  btrfs: add do_remap param to btrfs_discard_extent()
  btrfs: allow balancing remap tree
  btrfs: handle discarding fully-remapped block groups
  btrfs: add stripe removal pending flag

 fs/btrfs/Kconfig                |    2 +
 fs/btrfs/accessors.h            |   29 +
 fs/btrfs/block-group.c          |  280 ++++-
 fs/btrfs/block-group.h          |   23 +-
 fs/btrfs/block-rsv.c            |    8 +
 fs/btrfs/block-rsv.h            |    1 +
 fs/btrfs/discard.c              |   57 +-
 fs/btrfs/disk-io.c              |  107 +-
 fs/btrfs/extent-tree.c          |  137 ++-
 fs/btrfs/extent-tree.h          |    3 +-
 fs/btrfs/free-space-cache.c     |   82 +-
 fs/btrfs/free-space-cache.h     |    1 +
 fs/btrfs/free-space-tree.c      |    4 +-
 fs/btrfs/free-space-tree.h      |    5 +-
 fs/btrfs/fs.h                   |   10 +-
 fs/btrfs/inode.c                |    2 +-
 fs/btrfs/locking.c              |    1 +
 fs/btrfs/relocation.c           | 1866 ++++++++++++++++++++++++++++++-
 fs/btrfs/relocation.h           |   10 +-
 fs/btrfs/space-info.c           |   22 +-
 fs/btrfs/sysfs.c                |    4 +
 fs/btrfs/transaction.c          |   11 +
 fs/btrfs/tree-checker.c         |   94 +-
 fs/btrfs/tree-checker.h         |    5 +
 fs/btrfs/volumes.c              |  283 ++++-
 fs/btrfs/volumes.h              |   19 +-
 include/uapi/linux/btrfs.h      |    1 +
 include/uapi/linux/btrfs_tree.h |   30 +-
 28 files changed, 2889 insertions(+), 208 deletions(-)

-- 
2.49.1