# Test Case: Reserved Inode Format Rejection

**Test ID**: TC113-corrupted-inode
**Category**: Error Handling
**Priority**: Critical

## Objective

Verify a checksum-valid image mounts, but lookup/open of the resolved
`/inode-target.txt` inode with reserved `i_format` bit `0x8000` fails with
`EOPNOTSUPP`; an unaffected file must remain readable.

## Fixture Qualification

```sh
work=$(mktemp -d /tmp/repo22-tc113.XXXXXX)
tests/prepare_error_fixtures.sh "$work/fixtures"
cc -O2 -Wall -Wextra -std=c17 tests/read_probe.c -o "$work/read_probe"
python3 tests/erofs_fixture.py inspect \
  "$work/fixtures/bad-inode-format.erofs" --path /inode-target.txt
grep '^bad-inode-format ' "$work/fixtures/fixture-evidence.txt"
sha256 -q "$work/fixtures/bad-inode-format.erofs"
```

The mutator resolves the root dirent, calculates the inode byte offset from the
metadata block and NID, asserts the old format, sets only reserved bit
`0x8000`, recomputes CRC32C, and preserves provider length.

## FreeBSD Procedure

```sh
mkdir "$work/mnt"
unit=$(mdconfig -a -t vnode -f "$work/fixtures/bad-inode-format.erofs")
mount -t erofs -o ro "/dev/$unit" "$work/mnt"
cmp "$work/fixtures/source/control.txt" "$work/mnt/control.txt"
truss -o "$work/read.truss" "$work/read_probe" expect-error \
  "$work/mnt/inode-target.txt" 45 | tee "$work/error.out"
grep -q 'expected_errno=45' "$work/error.out"
grep -E '(openat|read).*ERR#45' "$work/read.truss"
cmp "$work/fixtures/source/control.txt" "$work/mnt/control.txt"
umount "$work/mnt"
mdconfig -d -u "${unit#md}"
```

## Expected Results

Only the target returns errno 45 (`EOPNOTSUPP`). The mount remains usable and
cleans up fully.