82 lines
3.4 KiB
Markdown
82 lines
3.4 KiB
Markdown
# Test Case: DEFLATE and ZSTD Partial References
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**Test ID**: TC143-deflate-zstd-partial-reference
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**G5 fixture contract**: Use [G5-MANUAL-SETUP.md](G5-MANUAL-SETUP.md).
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Its generated paths, source comparisons, structured corruption offsets, and
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cleanup rules supersede placeholder examples in this file.
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**Category**: Compression
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**Priority**: Critical
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**Regression**: Non-LZ4 partial-reference decoding
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## Objective
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Verify full and partial-reference decoding for raw DEFLATE and ZSTD streams,
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including exact full-file SHA256, cross-extent reads, random reads, and
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corrupted-stream `EIO` behavior.
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## Preconditions
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- FreeBSD 15 guest.
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- ZSTDIO-enabled repo22 module for the ZSTD cases.
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- Deterministic full-index fixtures whose layout parser proves:
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- the full file points at a complete compressed stream;
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- the partial file reuses that physical stream;
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- the reused HEAD record has `Z_EROFS_LI_PARTIAL_REF` (`0x8000`) set;
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- the reused first NONHEAD record has the complete source pcluster's
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`D0_CBLKCNT`, not the partial file's original compressed-block count;
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- the partial file's logical length is shorter than the source stream's
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decompressed length.
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- Corrupted copies produced only after locating the target compressed extent;
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do not use a blind image offset.
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## Layout Proof
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```sh
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dump.erofs -s deflate-partial-ref.erofs
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dump.erofs --path=/a.dat -e deflate-partial-ref.erofs
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dump.erofs --path=/b.dat -e deflate-partial-ref.erofs
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dump.erofs -s zstd-partial-ref.erofs
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dump.erofs --path=/a.dat -e zstd-partial-ref.erofs
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dump.erofs --path=/b.dat -e zstd-partial-ref.erofs
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```
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The byte-level fixture record must assert the original NID, map-header offset,
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HEAD record, pblk, and checksum before setting the partial-reference bit or
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redirecting a pblk.
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## Test Steps
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1. Mount the DEFLATE image and hash `/a.dat` and `/b.dat` completely.
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2. Read a range crossing a known DEFLATE logical extent boundary.
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3. Read another non-aligned random range and compare it byte-for-byte with the
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source.
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4. Repeat steps 1-3 for ZSTD.
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5. Mount each corrupted copy and read the targeted file through a small C
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errno probe.
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6. Compare pre/post `dmesg` and active `vmstat -m` EROFS allocations.
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The G5 DEFLATE partial is 100000 bytes because erofs-utils 1.8.6 splits the
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1 MiB DEFLATE source according to the 32 KiB DEFLATE window. It reuses the
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first 17-block source pcluster and uses offsets 65500/2048 and 90000/4096.
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The ZSTD partial is 700000 bytes and uses these checks:
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```sh
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dd if=/mnt/repo22/b.dat of=/tmp/guest bs=1 skip=122900 count=512 status=none
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dd if=source-b.dat of=/tmp/source bs=1 skip=122900 count=512 status=none
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cmp /tmp/guest /tmp/source
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dd if=/mnt/repo22/b.dat of=/tmp/guest bs=1 skip=524287 count=4097 status=none
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dd if=source-prefix-b.dat of=/tmp/source bs=1 skip=524287 count=4097 status=none
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cmp /tmp/guest /tmp/source
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```
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## Expected Results
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- Full DEFLATE and ZSTD streams require complete output and stream completion.
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- Partial references succeed after producing the requested logical prefix;
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they do not require the reused source frame to finish.
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- Complete SHA256 and every boundary/random byte comparison match.
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- Targeted corruption returns read errno 5 (`EIO`), with no leaked active
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allocation, panic, or trap.
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- `control.bin` in each corrupted image remains byte-identical to its source.
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## Cleanup
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Unmount each image, detach every md unit, remove temporary range outputs, and
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unload the module by its `kldstat` ID.
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