de_blk
bn = de_blk(pmp, length);
&& de_blk(pmp, diroffset + blsize) > pmp->pm_rootdirsize)
(de_blk((pmp), (dirofs)) + (pmp)->pm_rootdirblk)
&& de_blk(pmp, diroffset + blsize) > pmp->pm_rootdirsize)
(de_blk((pmp), (dirofs)) + (pmp)->pm_rootdirblk)