根据block取出页号buf_block_get_page_no

/*********************************************************************//**
Gets the page number of a block.
@return    page number */
UNIV_INLINE
ulint
buf_block_get_page_no(
/*==================*/
    const buf_block_t*    block)    /*!< in: pointer to the control block */
{
    ut_ad(block);
    ut_a(buf_block_get_state(block) == BUF_BLOCK_FILE_PAGE);

    return(block->page.offset);
}