Must have been V6; I recall V7 had patches to prevent this, at least to the extent that it wouldn't crater the whole machine. I haven't thought about using ncheck & icheck since fsdb showed up about BSD4.2 or thereabouts. I remember using adb as well to fix buggered filesystems back in the ancient days.

I remember well the day one of the elder neckbeards handed me my own photocopy of the Lions books. It was enlightenment in pure form.