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

Aurelien DESBRIERES
2026-04-14T10:07:30Z

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

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2.52.0