ffs_setblock
ffs_setblock(fs, blksfree, fragno);
void ffs_setblock(struct fs *, u_char *, int32_t);
ffs_setblock(fs, cg_blksfree(cgp, needswap), fragno);
void ffs_setblock(struct fs *, u_char *, int32_t);
ffs_setblock(&sblock, cg_blksfree(&acg, 0), blkno);
ffs_setblock(&sblock, cg_blksfree(&acg, 0), blkno);