and usr.sbin/makefs/ffs/ffs_subr.c as they have no need of anything in that
file. No other programs or libraries include <ufs/ffs/ffs_extern.h> (nor
should they as it is totally in-kernel interfaces). For added protection
I enclosed the entire contents of <ufs/ffs/ffs_extern.h> in ifdef _KERNEL.
Feedback from: Bruce Evans and Tai-hwa Liang
brings in support for an optional intent log which eliminates the need
for background fsck on unclean shutdown.
Sponsored by: iXsystems, Yahoo!, and Juniper.
With help from: McKusick and Peter Holm