repo22 non-LZ4 leading-zero verification

Date: 2026-08-08 UTC
Source baseline: 7cba92c0ec434b96180200b09e5dddfa213e67f5
FreeBSD guest: 15.0-RELEASE-p8 amd64, QEMU TCG
Image tool: erofs-utils 1.8.6
Scope: MicroLZMA, DEFLATE, and ZSTD leading-zero handling only

Code change

Linux 7.1-rc1 calls z_erofs_fixup_insize() for every MicroLZMA, DEFLATE, and ZSTD stream, while LZ4 only requires it when the LZ4_0PADDING feature is enabled. The FreeBSD dispatcher now applies the same predicate. Existing first-block limits, empty-input rejection, and input-length subtraction remain unchanged.

Build and module lifecycle

./build.sh completed successfully and produced build/erofs.ko with SHA256:

4b3459a02da29642cb8e61f58e34ff5266e668e86256937c91b8af7e0e31fdcb

FreeBSD 15 results:

lifecycle_kldload_rc=0
lifecycle_kldunload_rc=0
dmesg_delta_lines=0
dmesg_error_grep_rc=1

The last two lines mean the isolated lifecycle and read pass added no kernel messages, so no decompression, linker, panic, or integrity error was present.

Deterministic images

The source file was 1 MiB and had SHA256:

370eb0a8df86868c4842ca535ed64670f0277ea2ed47a703f089bbb13ee4ac52

The images were regenerated with erofs-utils 1.8.6:

mkfs.erofs -T0 --all-root --ignore-mtime -x-1 -Uclear \
  -zlzma,level=6 -C4096 lzma-root.erofs src-root
mkfs.erofs -T0 --all-root --ignore-mtime -x-1 -Uclear \
  -zdeflate,level=6 -C4096 deflate-root.erofs src-root
mkfs.erofs -T0 --all-root --ignore-mtime -x-1 -Uclear \
  -zzstd,level=3 -C4096 zstd-root.erofs src-root

dump.erofs reported layout 3 for /test-lz4.txt in all images. MicroLZMA and ZSTD used one 4096-byte physical extent; DEFLATE used two 4096-byte physical extents.

FreeBSD read results

Each image was attached with mdconfig, mounted read-only, read completely by sha256, unmounted, and detached before testing the next image.

lzma mount_rc=0 read_rc=0 sha256=370eb0a8df86868c4842ca535ed64670f0277ea2ed47a703f089bbb13ee4ac52
lzma umount_rc=0 detach_rc=0
deflate mount_rc=0 read_rc=0 sha256=370eb0a8df86868c4842ca535ed64670f0277ea2ed47a703f089bbb13ee4ac52
deflate umount_rc=0 detach_rc=0
zstd mount_rc=0 read_rc=0 sha256=370eb0a8df86868c4842ca535ed64670f0277ea2ed47a703f089bbb13ee4ac52
zstd umount_rc=0 detach_rc=0

Result: MicroLZMA, DEFLATE, and ZSTD all pass real-image full-file integrity verification on this FreeBSD 15 kernel configuration.

Notes and limits

An exploratory image with the file below a /files directory mounted, but the target lookup failed. Root-level fixtures were used to isolate decompression from the separately tracked directory lookup work. This does not change the three successful compressed read results above.

This batch does not claim coverage for other compression levels, large files, random access, corrupt streams, alternative FreeBSD kernel configurations, or other compression mapping features. DEFLATE and ZSTD kernel symbols were available on the tested FreeBSD 15 GENERIC kernel; no unsupported algorithm or kernel-symbol limitation was encountered.

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