# Test Case: Large Directory Block Index Width

**Test ID**: TC153-large-directory-block-index
**Category**: Directory Corruption
**Priority**: Critical
**Latest Result**: PASS on exact 9ae22009f FreeBSD 15 KLD; see the G3 report.

## Objective

Verify a valid extended FLAT_PLAIN/Layout0 directory with final block index
2147483648 enters the 64-bit lookup path and consistently reports sparse
midpoint corruption as EINTEGRITY.

## Procedure

Record final/tc153-sparse-evidence.txt and the sparse-prefix hash. Copy the
90112-byte prefix, extend the copy sparsely to 8796093091840 bytes, and verify
the prefix hash remains unchanged:

    cp large-dir-intmax-sparse-prefix.erofs TC153-provider.erofs
    truncate -s 8796093091840 TC153-provider.erofs
    stat -f 'provider_size=%z allocated_sectors=%b' TC153-provider.erofs
    unit=$(mdconfig -a -t vnode -f TC153-provider.erofs)
    diskinfo "/dev/$unit"
    mount -t erofs -o ro "/dev/$unit" /tmp/repo22-g3/mnt
    ./g3_vfs_probe stat /tmp/repo22-g3/mnt/huge
    ./g3_vfs_probe expect-error stat \
      /tmp/repo22-g3/mnt/huge/missing 97
    ./g3_vfs_probe expect-error stat \
      /tmp/repo22-g3/mnt/huge/missing 97
    ./readdir_probe /tmp/repo22-g3/mnt 128
    ./g3_vfs_probe expect-error stat \
      /tmp/repo22-g3/mnt/huge/missing 97

Unmount, detach, and remove the sparse copy.

## Expected Results

GEOM reports 8796093091840 bytes while host allocation remains sparse.
The /huge inode reports size 8796093026304 and Layout0 qualification records
directory_blocks=2147483649, last_block=2147483648. Both cold lookups and the
post-root-readdir lookup return errno 97, with no ENOENT cache masking, wrap,
hang, trap, or panic. Record prefix/KLD hashes and complete cleanup.