# Test Case: Indexed Chunk Data on the Primary Device

**Test ID**: TC093-chunk-single-device  
**Category**: Chunk-Based  
**Priority**: High

## Objective

Verify 8-byte chunk indexes whose device ID is zero without a device table.
This is not a 4-byte block-map substitute.

## Fixture

Use `single-indexed.erofs` from the fresh G6 generator.  It is derived from the
mkfs blob baseline by asserting each original `(high=0, device=1, pblk)`,
folding the new blob bytes behind the metadata block, changing every index to
`device=0`, adding one to each pblk, and removing the device-table feature.
`verify` must report `extra_devices=0` and `entry_size=8`.

## Manual procedure

```sh
I=/root/repo22-g6/images
S=/root/repo22-g6/sources/chunk
mkdir -p /mnt/g6
kldload /root/repo22-g6/erofs.ko
mdconfig -a -t vnode -f "$I/single-indexed.erofs" -u 90
mount -t erofs -o ro /dev/md90 /mnt/g6
sha256 "$S/indexed.bin" /mnt/g6/indexed.bin
cmp "$S/indexed.bin" /mnt/g6/indexed.bin
dd if="$S/indexed.bin" of=/tmp/tc093.expected bs=1 skip=28672 count=8192 2>/dev/null
dd if=/mnt/g6/indexed.bin of=/tmp/tc093.actual bs=1 skip=28672 count=8192 2>/dev/null
cmp /tmp/tc093.expected /tmp/tc093.actual
```

## Expected results

- Mount succeeds without any `device.N` option.
- Full-file and cross-32768-byte-chunk comparisons pass.
- No external GEOM provider or device-table lookup is attempted.

## Cleanup and zero-state check

```sh
umount /mnt/g6
mdconfig -d -u 90
kldunload erofs
rm -f /tmp/tc093.expected /tmp/tc093.actual
mount -p | awk '$3 == "erofs" { print }'
mdconfig -l
kldstat -n erofs 2>/dev/null || true
sysctl -n kern.geom.conftxt | grep -E 'md90|erofs' || true
```

All four final outputs must be empty.
