# Test Case: statfs with 48-bit Block Count

**Test ID**: TC010-statfs-48bit
**Category**: Filesystem Metadata
**Priority**: Medium

## Objective

Verify a nonzero 48-bit block-count high word survives mount validation and is
exported without truncation through FreeBSD `statfs(2)` and `df(1)`.

## Fixture Qualification

```sh
work=$(mktemp -d /tmp/repo22-tc010.XXXXXX)
tests/prepare_error_fixtures.sh "$work/fixtures"
python3 tests/erofs_fixture.py inspect \
  "$work/fixtures/48bit-statfs-prefix.erofs"
grep '^48bit-statfs-prefix ' "$work/fixtures/fixture-evidence.txt"
sha256 -q "$work/fixtures/48bit-statfs-prefix.erofs"
```

Read `total_blocks` and `required_provider_length` from the evidence. The
fixture sets incompat bit `0x80`, `rb.blocks_hi=1`, and a nonzero
`rootnid_8b`, then recomputes CRC32C. Its small prefix hash identifies the
metadata; the qualified provider is that exact prefix followed by sparse zeros
to the required media size.

## FreeBSD Procedure

```sh
provider="$work/48bit-statfs-provider.raw"
cp "$work/fixtures/48bit-statfs-prefix.erofs" "$provider"
truncate -s "$required_provider_length" "$provider"
stat -f 'size=%z blocks=%b' "$provider"
unit=$(mdconfig -a -t vnode -f "$provider")
diskinfo -v "/dev/$unit"
mkdir "$work/mnt"
mount -t erofs -o ro "/dev/$unit" "$work/mnt"
df -kT "$work/mnt"
df -iT "$work/mnt"
actual_1k=$(df -k "$work/mnt" | awk 'NR == 2 { print $2 }')
used_1k=$(df -k "$work/mnt" | awk 'NR == 2 { print $3 }')
avail_1k=$(df -k "$work/mnt" | awk 'NR == 2 { print $4 }')
expected_1k=$((total_blocks * 4))
test "$actual_1k" -eq "$expected_1k"
test "$used_1k" -eq "$expected_1k"
test "$avail_1k" -eq 0
umount "$work/mnt"
mdconfig -d -u "${unit#md}"
rm -f "$provider"
```

## Expected Results

`diskinfo` reports at least the declared 16 TiB-plus media size. Mount succeeds,
the `df -k` total equals `total_blocks * 4`, Used equals total because
`f_bfree=0`, and Avail is zero.
If the filesystem cannot create or attach the sparse provider, record SHELVED
with all failed commands; a short-provider `ENXIO` is not PASS.