VBLKSHIFT
vbaddr = fsbtodb(&fs, addr2) + (off >> VBLKSHIFT) * DBPERVBLK;
#define VBLKSIZE (1 << VBLKSHIFT)
#define INDIRPERVBLK(fs) (NINDIR(fs) / ((fs)->fs_bsize >> VBLKSHIFT))
#define IPERVBLK(fs) (INOPB(fs) / ((fs)->fs_bsize >> VBLKSHIFT))