=== DF-0858 fix validation (Phase 8) ===
Kernel: DragonFly 6.5-DEVELOPMENT #0: Thu Jul  2 06:02:54 UTC 2026
Module: patched hpfs.ko (sha256 d23a53566d6ddd0f8c80a1d261ddba7f554444a4f36748ef4b0153a243db6498)
Image:  df858.img (cyclic AlSec A<->B)

--- mount (root) ---
mount_hpfs: /dev/vn0: Device busy
MOUNT_RC=71

--- trigger (unprivileged maxx) ---
CAT_EXIT=0
cat: /mnt/FILE: Invalid argument
        0.00 real         0.00 user         0.01 sys

--- dmesg (depth-cap kprintf) ---
hpfs_hpbmap: dive depth 22 exceeds 20 (cyclic or corrupt AlSec tree)
hpfs_hpbmap: dive depth 22 exceeds 20 (cyclic or corrupt AlSec tree)

RESULT: cat returned EINVAL in <1ms (no kernel spin) — FIX WORKS