Please see:  <http://www.netbsd.org/~bjs/ufs_dirhash.c.diff>.

For the rationale for the changes to PR_NOWAIT, MALLOC/memset ->
malloc+M_ZERO, and MALLOC(dh ...) -> dh = malloc(dh ...), see the
commit messages
for revs. 1.1{7,6,4,3} at:

<http://www.openbsd.org/cgi-bin/cvsweb/src/sys/ufs/ufs/ufs_dirhash.c>.

Also, daddr_t is int64_t; the hash table is two levels, so, if I
understand this correctly at all, we're allocating twice as much
memory as we need to be.