[PATCH v3 00/12] ftrfs: Fault-Tolerant Radiation-Robust Filesystem

[Aurelien DESBRIERES <aurelien@hackers.camp>]

This is v3 of the FTRFS patch series. FTRFS is a Linux kernel filesystem
designed for dependable storage in radiation-intensive environments,
implementing Reed-Solomon FEC at the filesystem block level for in-place
correction of silent bit flips on single-device embedded systems (MRAM,
NOR flash) without external redundancy.

Based on: Fuchs, Langer, Trinitis - ARCS 2015, TU Munich / MOVE-II CubeSat.
Full text: https://www.cfuchs.net/chris/publication-list/ARCS2015/FTRFS.pdf

Changes since v2 (<20260413230601.525400-1-aurelien@hackers.camp>):

  - iomap IO path: replace buffer_head based read/write with iomap API
    as requested by Matthew Wilcox. Implements ftrfs_iomap_begin/end,
    iomap_writeback_ops (writeback_range/writeback_submit), and uses
    iomap_bio_read_ops for the read path. buffer_head is retained for
    metadata IO (inode table, directory blocks) as discussed.

  - rename: implement ftrfs_rename in namei.c. Handles same-dir and
    cross-dir rename for files and directories, updates '..' entries
    and nlink counts. RENAME_EXCHANGE and RENAME_WHITEOUT return
    -EINVAL (not supported in v3).

  - RS FEC decoder: implement full RS(255,239) decoder in edac.c using
    Berlekamp-Massey error locator polynomial, Chien search, and Forney
    algorithm for in-place correction. Corrects up to 8 symbol errors
    per 255-byte subblock. Returns -EBADMSG if uncorrectable.

  - Radiation Event Journal: persistent ring buffer of 64 x 24 bytes
    in the superblock reserved area. Records block number, timestamp
    (ns), symbols corrected, and per-entry CRC32 for each RS correction
    event. Written under spinlock via ftrfs_log_rs_event(). No existing
    Linux filesystem provides this filesystem-level radiation event
    history - VxWorks HRFS, btrfs scrub, and NVMe SMART all operate
    at different layers.

AI tooling disclosure (Documentation/process/coding-assistants.rst):
  Assisted-by: Claude:claude-sonnet-4-6
  The submitter takes full responsibility for all code, has reviewed,
  tested, and debugged every patch.

Testing:
  - qemuarm64, kernel 7.0 final (Yocto Styhead 5.1, cortex-a57 TCG)
  - mount, write, read, rename, umount: 0 BUG/WARN/Oops
  - xfstests generic/001, 002, 010 equivalent: all pass
  - Slurm 25.11.4 HPC cluster validation (3-node parallel jobs)
  - checkpatch.pl: 0 errors, 0 warnings on all modified files

HPC/space use case:
  FTRFS is validated in an arm64 Slurm cluster built with Yocto
  (github.com/roastercode/yocto-hardened, branch arm64-ftrfs).
  This demonstrates the filesystem operating in a real HPC embedded
  context, not just a test image - the target environment for
  space-grade embedded Linux systems.

Remaining work (v4):
  - kthread scrubber with RT priority and sysfs interface
  - Full xfstests Yocto recipe
  - iomap for metadata IO path (currently buffer_head)

Aurelien DESBRIERES (12):
  ftrfs: add on-disk format and in-memory data structures
  ftrfs: add superblock operations
  ftrfs: add inode operations
  ftrfs: add directory operations
  ftrfs: add file operations
  ftrfs: add block and inode allocator
  ftrfs: add filename and directory entry operations
  ftrfs: add CRC32 checksumming and Reed-Solomon FEC skeleton
  ftrfs: add Kconfig, Makefile and fs/ tree integration
  MAINTAINERS: add entry for FTRFS filesystem
  ftrfs: v2 fixes - write path, inode lifecycle, on-disk format
  ftrfs: v3 - iomap IO path, rename, RS decoder, Radiation Event Journal

 MAINTAINERS       |   6 +
 fs/ftrfs/Kconfig  |  49 +++++
 fs/ftrfs/Makefile |  46 ++++
 fs/ftrfs/alloc.c  | 251 +++++++++++++++++++++
 fs/ftrfs/dir.c    | 126 +++++++++++
 fs/ftrfs/edac.c   | 277 +++++++++++++++++++++++
 fs/ftrfs/file.c   | 197 +++++++++++++++++
 fs/ftrfs/ftrfs.h  | 201 +++++++++++++++++
 fs/ftrfs/inode.c  | 104 +++++++++
 fs/ftrfs/namei.c  | 548 ++++++++++++++++++++++++++++++++++++++++++++++
 fs/ftrfs/super.c  | 317 +++++++++++++++++++++++++++
 11 files changed, 2122 insertions(+)
 create mode 100644 fs/ftrfs/Kconfig
 create mode 100644 fs/ftrfs/Makefile
 create mode 100644 fs/ftrfs/alloc.c
 create mode 100644 fs/ftrfs/dir.c
 create mode 100644 fs/ftrfs/edac.c
 create mode 100644 fs/ftrfs/file.c
 create mode 100644 fs/ftrfs/ftrfs.h
 create mode 100644 fs/ftrfs/inode.c
 create mode 100644 fs/ftrfs/namei.c
 create mode 100644 fs/ftrfs/super.c

-- 
2.52.0