ffs_setblock
ffs_setblock(fs, cg_blksfree(cgp), blkno);
void ffs_setblock(struct fs *, u_char *, daddr_t);
void ffs_setblock(struct fs *, u_char *, daddr_t);
void ffs_setblock(struct fs *, u_char *, int32_t);
ffs_setblock(&sblock, cg_blksfree(&acg), blkno);
ffs_setblock(&sblock, cg_blksfree(&acg), blkno);