bufnode_buf
bp = bufnode_buf(ch_bufhead);
bp = bufnode_buf(bn);
bufnode_buf(ch_buftail)->block != -1) {
bp = bufnode_buf(bn);
bp = bufnode_buf(bn);
bp = bufnode_buf(bn);
if (bufnode_buf(bn)->block < bufnode_buf(firstbn)->block)
ch_block = bufnode_buf(firstbn)->block;
bufnode_buf(bn)->block = -1;
free(bufnode_buf(bn));