qnx4_block_map
blknum = qnx4_block_map(inode, ctx->pos >> QNX4_BLOCK_SIZE_BITS);
phys = qnx4_block_map( inode, iblock );
block = qnx4_block_map(dir, blkofs);
extern unsigned long qnx4_block_map(struct inode *inode, long iblock);