cab6cd67bc
kernel refuse to mount a filesystem read-write (booting a system multiuser with critical filesystems read-only is bad): Add a check_wapbl() which will check some WAPBL values in the superblock, and try to read the journal via wapbl_replay_start() if there is one. pfatal() if one of these fail (abort boot if in preen mode, as "CONTINUE" otherwise). In non-preen mode the bogus journal will be cleared. check_wapbl() is always called if the superblock supports WAPBL. Even if FS_DOWAPBL is not there, there could be flags asking the kernel to clear or create a log with bogus values which would cause the kernel refuse to mount the filesystem. Discussed in http://mail-index.netbsd.org/tech-kern/2009/08/17/msg005896.html and followups.