72 lines
3.9 KiB
Markdown
72 lines
3.9 KiB
Markdown
 
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# Changelog
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All notable changes to this project are documented in this file, in the
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style of [Keep a Changelog](https://keepachangelog.com/en/1.1.0/). This
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project follows [Semantic Versioning](https://semver.org/); see
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`PACKFS_VERSION_STRING` in `include/packfs.h` for the authoritative current
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version (`packfs.pc`, generated by `make install`, is derived from it, not
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maintained separately).
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No version has been tagged yet — this project is pre-release (`0.x`, an
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initial, partial implementation of `concept.md`, not a completed one; see
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`README.md`'s "Status"). Entries below are grouped as they will read once
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`0.1.0` is tagged.
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## [Unreleased]
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### Added
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- Initial implementation of `concept.md`: `vfs_*` core, `mem`/`dir`/`pack`
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backends, the copy-on-write overlay (copy-up, whiteouts, compaction, an
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append journal), path containment (`openat2`/Landlock on Linux 5.6+/5.13+,
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a documented weaker fallback elsewhere), and pack integrity validation.
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- `tests/test_*.c` covering each backend, concurrency, and randomized
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structural-index stress testing against an independent reference model.
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- `bench/bench.c` (`make bench`) and `BENCH.md`, comparing PackFS against
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the host filesystem across metadata operations, large sequential I/O,
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random-access pack reads, mount-table scaling, and concurrent workloads.
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- `PACKFS_VERSION_MAJOR`/`MINOR`/`PATCH`/`STRING` and `pfs_version()` for
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compile-time and runtime version/ABI checks.
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- `packfs.pc` (pkg-config), generated by `make install` from
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`packfs.pc.in`, version always derived from `include/packfs.h`.
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- `SPDX-License-Identifier: MIT` on every file under `src/` and
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`include/`.
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### Fixed
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- **Bulk sequential `create`/`unlink`/`mkdir` on `mem`/`dir` was O(n²) in
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file count.** The index (`UpperSnapshot`) was a flat sorted array copied
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in full on every structural write; rewritten as a persistent treap
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(`src/upper.c`), reducing a structural write to the O(log n) nodes on
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the path to the change. See `BENCH.md`'s "Resolution" for the full
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before/after measurement and complexity-class confirmation.
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- **`pack_write`'s compaction-time exact-duplicate elimination (Section
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9.2) was O(n²) in entry count, and trusted a hash match without
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comparing actual bytes** (a latent correctness bug: FNV-1a64 is
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explicitly not collision-resistant). Rewritten as an open-addressing
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hash table with a `memcmp` verification before ever reusing a
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`data_off`, fixing both at once. See `BENCH.md`'s "Resolution #2".
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- **`backend_pack_new` was declared in `include/packfs.h` but never
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implemented** — any program calling it failed at link time. Implemented
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as a standalone, read-only `pack` `Backend`.
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- `.github/workflows/ci.yml`'s sanitizer-build steps never passed
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`-D_GNU_SOURCE` when compiling test files (only the library object
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files got it), which was harmless until a test included `internal.h`
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(needed for `pthread_rwlock_t`) and became a link failure.
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### Documented
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- **`vfs.c`'s mount table (`MountSnapshot`) is O(n²) in mount count, the
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same pattern the file index used to have — confirmed, and deliberately
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left unfixed.** Mount counts are bounded by a program's own source code,
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not workload-driven, so they do not reach the scale that made the file
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index's O(n²) a real problem. See `BENCH.md`'s "Finding: mount table
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scaling" for the numbers and reasoning.
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- A ThreadSanitizer environment limitation (some sandboxes block the
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`personality(ADDR_NO_RANDOMIZE)` syscall TSan needs) and a related
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ASan/UBSan sandbox startup flake (`AddressSanitizer:DEADLYSIGNAL`),
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both in `CONTRIBUTING.md` and `CLAUDE.md`, with the confirming tests and
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the required mitigation (`timeout`-wrapped sanitizer runs).
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<!-- This repository has no remote configured yet (see `git remote -v`),
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so there is no comparison-link URL to cite here truthfully; add
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"[Unreleased]: <repo-url>/compare/v0.1.0...HEAD" once one exists and
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v0.1.0 is tagged, per Keep a Changelog's own convention. -->
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