根据block取出space_id

/*********************************************************************//**
Gets the space id of a block.
@return    space id */
UNIV_INLINE
ulint
buf_block_get_space(
/*================*/
    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.space);
}