do_blkswap
extern int do_blkswap; /* need to do block addr byteswap */
if (do_blkswap) { /* swap byte order of the whole blk */
int do_blkswap;
do_blkswap = 0; /* has been done */
doswap = do_blkswap = do_dirswap = 0;
doswap = do_blkswap = do_dirswap = 1;
doswap = do_blkswap = do_dirswap = 0;
doswap = do_blkswap = do_dirswap = 1;
int do_blkswap;