test code v1

docs/features.md

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+# EROFS Feature Status
+
+This list describes behavior implemented and manually qualified in the
+FreeBSD 15 module. It is not a claim of complete Linux EROFS feature parity.
+
+## Filesystem and Metadata
+
+- Read-only mount/unmount and `statfs`.
+- Superblock CRC32C, declared image/media bounds, 48-bit block/root-NID decode.
+- Compact and extended inodes.
+- Correct compact non-directory `I_NLINK_1` semantics and directory
+  `dot_omitted` semantics.
+- Linux `new_decode_dev` major/minor decoding followed by FreeBSD `makedev()`.
+- Superblock-seeded, inode-metadata-derived vnode/NFS generation synchronized
+  with `va_gen`; metadata-identical payload replacement is outside the stale
+  handle guarantee.
+- NFS export, 64-bit NID file handles, stale-generation and malformed-FID
+  validation.
+
+## Data Layouts
+
+- `FLAT_PLAIN` and `FLAT_INLINE` reads.
+- Inline tails constrained to the inode metadata block and declared backing
+  bounds.
+- Chunk-based files, chunk indexes, holes, device tables, explicit devices,
+  and flatdev mapping.
+- LZ4, MicroLZMA, DEFLATE, and ZSTD compressed reads.
+- Full and compact indexes, partial references, HEAD2/interlaced records,
+  ztailpacking, and fragment-backed compressed data used by qualified images.
+- Compressed `va_bytes`/`st_blocks` from the complete 48-bit on-disk compressed
+  block count; plain, inline, and chunk files retain logical block rounding.
+
+## Vnode and Directory Operations
+
+- `vget`, root lookup, `vfs_hash`, namecache, and `vn_vget_ino` integration.
+- `lookup`, `readdir`, stable restart cookies, cold nested lookup, and
+  Linux-compatible nonzero final-name padding.
+- Shared strict validation for dirent arrays, `nameoff`, block bounds, and
+  illegal names.
+- `getattr`, access checks, `readlink`, `pathconf`, and read-only mutation
+  rejection, including combined special-vnode setattr requests.
+- FreeBSD 15 `vnode_pager_local_getpages` and compatible async pager entry;
+  `VOP_BMAP` remains explicitly unsupported.
+
+## Xattrs and ACLs
+
+- Inline and shared `user.*`, `trusted.*`, and `security.*` attributes.
+- Shared attributes in primary metadata and metabox containers.
+- Long-prefix and packed-prefix-table lookup.
+- FreeBSD user/system namespace exposure and POSIX access/default ACL reads.
+- Read-only xattr/ACL mutation behavior.
+
+## Documentation and Validation
+
+- `erofs(5)` manual page.
+- Markdown manual tests TC001-TC161, with unresolved cases tracked in
+  `issues/`.
+- FreeBSD 15 manual reports with fixture hashes and cleanup evidence.
+- Final explicit-extent ordering, 48-bit allocation, special setattr,
+  `OFF_MAX` directory-cookie, and build-tool failure checks.
+
+## Build Qualification
+
+- FreeBSD 15 `amd64` is the only currently validated and accepted target;
+  `src/Makefile` rejects other architectures.
+- ZSTD support is disabled by default (`WITH_ZSTDIO=0`). Opt-in builds use
+  `WITH_ZSTDIO=1` and require a kernel built with `options ZSTDIO`.
+
+## Not Implemented or Not Claimed
+
+- Writable filesystem operations.
+- A CI pipeline or automated kernel-test harness.
+- Positive mapped-payload execution of the explicit compressed-extent format;
+  TC146 remains PARTIAL and the fixture limitation is tracked under `issues/`.
+- Blanket support for every future EROFS incompat feature or every dedupe
+  encoding; only the explicitly qualified fragment/metabox forms are claimed.
+- Performance guarantees from the manual throughput observations.