取出block所对应的hash值

/**********************************************************************//**
Gets the hash value of the page the pointer is pointing to. This can be used
in searches in the lock hash table.
@return    lock hash value */
UNIV_INLINE
ulint
buf_block_get_lock_hash_val(
/*========================*/
    const buf_block_t*    block)    /*!< in: block */
{
    ut_ad(block);
    ut_ad(buf_page_in_file(&block->page));
#ifdef UNIV_SYNC_DEBUG
    ut_ad(rw_lock_own(&(((buf_block_t*) block)->lock), RW_LOCK_EXCLUSIVE)
          || rw_lock_own(&(((buf_block_t*) block)->lock), RW_LOCK_SHARED));
#endif /* UNIV_SYNC_DEBUG */
    return(block->lock_hash_val);
}