dm-verity: more FEC fixes and cleanups

This series applies to linux-dm/for-next. It can also be retrieved from:

    git fetch https://git.kernel.org/pub/scm/linux/kernel/git/ebiggers/linux.git dm-verity-fec-2026-02-05

Patches 1-5 fix bugs in dm-verity's forward error correction (FEC):

- FEC and hash devices that are too small were not rejected.

- Corrected blocks could be multiple-counted in statistics.

- The erasures array was significantly oversized for its use case.

- An out-of-bounds read could occur when decoding an RS codeword whose parity bytes span a block boundary.

Patches 6-22 clean up the FEC implementation to be easier to understand and improve documentation and log messages.

Eric Biggers (22):
dm-verity-fec: correctly reject too-small FEC devices
dm-verity-fec: correctly reject too-small hash devices
dm-verity-fec: fix corrected block count stat
dm-verity-fec: fix the size of dm_verity_fec_io::erasures
dm-verity-fec: fix reading parity bytes split across blocks (take 3)
dm-verity: rename dm_verity::hash_blocks to dm_verity::hash_end
dm-verity-fec: improve documentation for Forward Error Correction
dm-verity-fec: replace {MAX,MIN}_RSN with {MIN,MAX}_ROOTS
dm-verity-fec: use standard names for Reed-Solomon parameters
dm-verity-fec: rename "RS block" to "RS codeword"
dm-verity-fec: replace io_size with block_size
dm-verity-fec: rename rounds to region_blocks
dm-verity-fec: simplify computation of rsb
dm-verity-fec: simplify computation of ileaved
dm-verity-fec: simplify deinterleaving
dm-verity-fec: rename block_offset to out_pos
dm-verity-fec: move computation of offset and rsb down a level
dm-verity-fec: compute target region directly
dm-verity-fec: pass down index_in_region instead of rsb
dm-verity-fec: make fec_decode_bufs() just return 0 or error
dm-verity-fec: log target_block instead of index_in_region
dm-verity-fec: improve comments for fec_read_bufs()

 .../admin-guide/device-mapper/verity.rst      | 122 +++++-
 drivers/md/dm-verity-fec.c                    | 380 ++++++++----------
 drivers/md/dm-verity-fec.h                    |  28 +-
 drivers/md/dm-verity-target.c                 |   8 +-
 drivers/md/dm-verity.h                        |   4 +-
 5 files changed, 294 insertions(+), 248 deletions(-)

base-commit: 218b16992a37ea97b9e09b7659a25a864fb9976f

2.52.0