path: root/storage/xtradb/include/buf0buf.h

/*****************************************************************************

Copyright (c) 1995, 2013, Oracle and/or its affiliates. All Rights Reserved.

This program is free software; you can redistribute it and/or modify it under
the terms of the GNU General Public License as published by the Free Software
Foundation; version 2 of the License.

This program is distributed in the hope that it will be useful, but WITHOUT
ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

You should have received a copy of the GNU General Public License along with
this program; if not, write to the Free Software Foundation, Inc.,
51 Franklin Street, Suite 500, Boston, MA 02110-1335 USA

*****************************************************************************/

/**************************************************//**
@file include/buf0buf.h
The database buffer pool high-level routines

Created 11/5/1995 Heikki Tuuri
*******************************************************/

#ifndef buf0buf_h
#define buf0buf_h

#include "univ.i"
#include "fil0fil.h"
#include "mtr0types.h"
#include "buf0types.h"
#include "hash0hash.h"
#include "ut0byte.h"
#include "page0types.h"
#ifndef UNIV_HOTBACKUP
#include "ut0rbt.h"
#include "os0proc.h"

/** @name Modes for buf_page_get_gen */
/* @{ */
#define BUF_GET			10	/*!< get always */
#define	BUF_GET_IF_IN_POOL	11	/*!< get if in pool */
#define BUF_PEEK_IF_IN_POOL	12	/*!< get if in pool, do not make
					the block young in the LRU list */
#define BUF_GET_NO_LATCH	14	/*!< get and bufferfix, but
					set no latch; we have
					separated this case, because
					it is error-prone programming
					not to set a latch, and it
					should be used with care */
#define BUF_GET_IF_IN_POOL_OR_WATCH	15
					/*!< Get the page only if it's in the
					buffer pool, if not then set a watch
					on the page. */
#define BUF_GET_POSSIBLY_FREED		16
					/*!< Like BUF_GET, but do not mind
					if the file page has been freed. */
/* @} */
/** @name Modes for buf_page_get_known_nowait */
/* @{ */
#define BUF_MAKE_YOUNG	51		/*!< Move the block to the
					start of the LRU list if there
					is a danger that the block
					would drift out of the buffer
					pool*/
#define BUF_KEEP_OLD	52		/*!< Preserve the current LRU
					position of the block. */
/* @} */

#define MAX_BUFFER_POOLS_BITS	6 	/*!< Number of bits to representing
					a buffer pool ID */
#define MAX_BUFFER_POOLS	(1 << MAX_BUFFER_POOLS_BITS)
					/*!< The maximum number of buffer
					pools that can be defined */

#define BUF_POOL_WATCH_SIZE 1		/*!< Maximum number of concurrent
					buffer pool watches */

extern	buf_pool_t*	buf_pool_ptr;	/*!< The buffer pools
					of the database */
#ifdef UNIV_DEBUG
extern ibool		buf_debug_prints;/*!< If this is set TRUE, the program
					prints info whenever read or flush
					occurs */
#endif /* UNIV_DEBUG */
extern ulint srv_buf_pool_write_requests; /*!< variable to count write request
					  issued */
extern ulint srv_buf_pool_instances;
extern ulint srv_buf_pool_curr_size;
#else /* !UNIV_HOTBACKUP */
extern buf_block_t*	back_block1;	/*!< first block, for --apply-log */
extern buf_block_t*	back_block2;	/*!< second block, for page reorganize */
#endif /* !UNIV_HOTBACKUP */

/** Magic value to use instead of checksums when they are disabled */
#define BUF_NO_CHECKSUM_MAGIC 0xDEADBEEFUL

/** @brief States of a control block
@see buf_page_struct

The enumeration values must be 0..7. */
enum buf_page_state {
	BUF_BLOCK_ZIP_FREE = 0,		/*!< contains a free
					compressed page */
	BUF_BLOCK_POOL_WATCH = 0,	/*!< a sentinel for the buffer pool
					watch, element of buf_pool->watch[] */
	BUF_BLOCK_ZIP_PAGE,		/*!< contains a clean
					compressed page */
	BUF_BLOCK_ZIP_DIRTY,		/*!< contains a compressed
					page that is in the
					buf_pool->flush_list */

	BUF_BLOCK_NOT_USED,		/*!< is in the free list;
					must be after the BUF_BLOCK_ZIP_
					constants for compressed-only pages
					@see buf_block_state_valid() */
	BUF_BLOCK_READY_FOR_USE,	/*!< when buf_LRU_get_free_block
					returns a block, it is in this state */
	BUF_BLOCK_FILE_PAGE,		/*!< contains a buffered file page */
	BUF_BLOCK_MEMORY,		/*!< contains some main memory
					object */
	BUF_BLOCK_REMOVE_HASH		/*!< hash index should be removed
					before putting to the free list */
};


/** This structure defines information we will fetch from each buffer pool. It
will be used to print table IO stats */
struct buf_pool_info_struct{
	/* General buffer pool info */
	ulint	pool_unique_id;		/*!< Buffer Pool ID */
	ulint	pool_size;		/*!< Buffer Pool size in pages */
	ulint	pool_size_bytes;
	ulint	lru_len;		/*!< Length of buf_pool->LRU */
	ulint	old_lru_len;		/*!< buf_pool->LRU_old_len */
	ulint	free_list_len;		/*!< Length of buf_pool->free list */
	ulint	flush_list_len;		/*!< Length of buf_pool->flush_list */
	ulint	n_pend_unzip;		/*!< buf_pool->n_pend_unzip, pages
					pending decompress */
	ulint	n_pend_reads;		/*!< buf_pool->n_pend_reads, pages
					pending read */
	ulint	n_pending_flush_lru;	/*!< Pages pending flush in LRU */
	ulint	n_pending_flush_list;	/*!< Pages pending flush in FLUSH
					LIST */
	ulint	n_pending_flush_single_page;/*!< Pages pending flush in
					BUF_FLUSH_SINGLE_PAGE list */
	ulint	n_pages_made_young;	/*!< number of pages made young */
	ulint	n_pages_not_made_young;	/*!< number of pages not made young */
	ulint	n_pages_read;		/*!< buf_pool->n_pages_read */
	ulint	n_pages_created;	/*!< buf_pool->n_pages_created */
	ulint	n_pages_written;	/*!< buf_pool->n_pages_written */
	ulint	n_page_gets;		/*!< buf_pool->n_page_gets */
	ulint	n_ra_pages_read_rnd;	/*!< buf_pool->n_ra_pages_read_rnd,
					number of pages readahead */
	ulint	n_ra_pages_read;	/*!< buf_pool->n_ra_pages_read, number
					of pages readahead */
	ulint	n_ra_pages_evicted;	/*!< buf_pool->n_ra_pages_evicted,
					number of readahead pages evicted
					without access */
	ulint	n_page_get_delta;	/*!< num of buffer pool page gets since
					last printout */

	/* Buffer pool access stats */
	double	page_made_young_rate;	/*!< page made young rate in pages
					per second */
	double	page_not_made_young_rate;/*!< page not made young rate
					in pages per second */
	double	pages_read_rate;	/*!< num of pages read per second */
	double	pages_created_rate;	/*!< num of pages create per second */
	double	pages_written_rate;	/*!< num of  pages written per second */
	ulint	page_read_delta;	/*!< num of pages read since last
					printout */
	ulint	young_making_delta;	/*!< num of pages made young since
					last printout */
	ulint	not_young_making_delta;	/*!< num of pages not make young since
					last printout */

	/* Statistics about read ahead algorithm.  */
	double	pages_readahead_rnd_rate;/*!< random readahead rate in pages per
					second */
	double	pages_readahead_rate;	/*!< readahead rate in pages per
					second */
	double	pages_evicted_rate;	/*!< rate of readahead page evicted
					without access, in pages per second */

	/* Stats about LRU eviction */
	ulint	unzip_lru_len;		/*!< length of buf_pool->unzip_LRU
					list */
	/* Counters for LRU policy */
	ulint	io_sum;			/*!< buf_LRU_stat_sum.io */
	ulint	io_cur;			/*!< buf_LRU_stat_cur.io, num of IO
					for current interval */
	ulint	unzip_sum;		/*!< buf_LRU_stat_sum.unzip */
	ulint	unzip_cur;		/*!< buf_LRU_stat_cur.unzip, num
					pages decompressed in current
					interval */
};

typedef struct buf_pool_info_struct	buf_pool_info_t;

/** The occupied bytes of lists in all buffer pools */
struct buf_pools_list_size_struct {
	ulint	LRU_bytes;		/*!< LRU size in bytes */
	ulint	unzip_LRU_bytes;	/*!< unzip_LRU size in bytes */
	ulint	flush_list_bytes;	/*!< flush_list size in bytes */
};

typedef struct buf_pools_list_size_struct	buf_pools_list_size_t;

#ifndef UNIV_HOTBACKUP
/********************************************************************//**
Acquire mutex on all buffer pool instances */
UNIV_INLINE
void
buf_pool_mutex_enter_all(void);
/*===========================*/

/********************************************************************//**
Release mutex on all buffer pool instances */
UNIV_INLINE
void
buf_pool_mutex_exit_all(void);
/*==========================*/

/********************************************************************//**
*/
UNIV_INLINE
void
buf_pool_page_hash_x_lock_all(void);
/*================================*/

/********************************************************************//**
*/
UNIV_INLINE
void
buf_pool_page_hash_x_unlock_all(void);
/*==================================*/

/********************************************************************//**
Creates the buffer pool.
@return	own: buf_pool object, NULL if not enough memory or error */
UNIV_INTERN
ulint
buf_pool_init(
/*=========*/
	ulint	size,		/*!< in: Size of the total pool in bytes */
	ibool	populate,	/*!< in: Force virtual page preallocation */
	ulint	n_instances);	/*!< in: Number of instances */
/********************************************************************//**
Frees the buffer pool at shutdown.  This must not be invoked before
freeing all mutexes. */
UNIV_INTERN
void
buf_pool_free(
/*==========*/
	ulint	n_instances);	/*!< in: numbere of instances to free */

/********************************************************************//**
Clears the adaptive hash index on all pages in the buffer pool. */
UNIV_INTERN
void
buf_pool_clear_hash_index(void);
/*===========================*/

/********************************************************************//**
Relocate a buffer control block.  Relocates the block on the LRU list
and in buf_pool->page_hash.  Does not relocate bpage->list.
The caller must take care of relocating bpage->list. */
UNIV_INTERN
void
buf_relocate(
/*=========*/
	buf_page_t*	bpage,	/*!< in/out: control block being relocated;
				buf_page_get_state(bpage) must be
				BUF_BLOCK_ZIP_DIRTY or BUF_BLOCK_ZIP_PAGE */
	buf_page_t*	dpage);	/*!< in/out: destination control block */
/*********************************************************************//**
Gets the current size of buffer buf_pool in bytes.
@return	size in bytes */
UNIV_INLINE
ulint
buf_pool_get_curr_size(void);
/*========================*/
/*********************************************************************//**
Gets the current size of buffer buf_pool in frames.
@return	size in pages */
UNIV_INLINE
ulint
buf_pool_get_n_pages(void);
/*=======================*/
/********************************************************************//**
Gets the smallest oldest_modification lsn for any page in the pool. Returns
zero if all modified pages have been flushed to disk.
@return	oldest modification in pool, zero if none */
UNIV_INTERN
ib_uint64_t
buf_pool_get_oldest_modification(void);
/*==================================*/
/********************************************************************//**
Allocates a buf_page_t descriptor. This function must succeed. In case
of failure we assert in this function. */
UNIV_INLINE
buf_page_t*
buf_page_alloc_descriptor(void)
/*===========================*/
	__attribute__((malloc));
/********************************************************************//**
Free a buf_page_t descriptor. */
UNIV_INLINE
void
buf_page_free_descriptor(
/*=====================*/
	buf_page_t*	bpage)	/*!< in: bpage descriptor to free. */
	__attribute__((nonnull));

/********************************************************************//**
Allocates a buffer block.
@return	own: the allocated block, in state BUF_BLOCK_MEMORY */
UNIV_INTERN
buf_block_t*
buf_block_alloc(
/*============*/
	buf_pool_t*	buf_pool);	/*!< in: buffer pool instance,
					or NULL for round-robin selection
					of the buffer pool */
/********************************************************************//**
Frees a buffer block which does not contain a file page. */
UNIV_INLINE
void
buf_block_free(
/*===========*/
	buf_block_t*	block);	/*!< in, own: block to be freed */
#endif /* !UNIV_HOTBACKUP */
/*********************************************************************//**
Copies contents of a buffer frame to a given buffer.
@return	buf */
UNIV_INLINE
byte*
buf_frame_copy(
/*===========*/
	byte*			buf,	/*!< in: buffer to copy to */
	const buf_frame_t*	frame);	/*!< in: buffer frame */
#ifndef UNIV_HOTBACKUP
/**************************************************************//**
NOTE! The following macros should be used instead of buf_page_get_gen,
to improve debugging. Only values RW_S_LATCH and RW_X_LATCH are allowed
in LA! */
#define buf_page_get(SP, ZS, OF, LA, MTR)	 buf_page_get_gen(\
				SP, ZS, OF, LA, NULL,\
				BUF_GET, __FILE__, __LINE__, MTR)
/**************************************************************//**
Use these macros to bufferfix a page with no latching. Remember not to
read the contents of the page unless you know it is safe. Do not modify
the contents of the page! We have separated this case, because it is
error-prone programming not to set a latch, and it should be used
with care. */
#define buf_page_get_with_no_latch(SP, ZS, OF, MTR)	   buf_page_get_gen(\
				SP, ZS, OF, RW_NO_LATCH, NULL,\
				BUF_GET_NO_LATCH, __FILE__, __LINE__, MTR)
/********************************************************************//**
This is the general function used to get optimistic access to a database
page.
@return	TRUE if success */
UNIV_INTERN
ibool
buf_page_optimistic_get(
/*====================*/
	ulint		rw_latch,/*!< in: RW_S_LATCH, RW_X_LATCH */
	buf_block_t*	block,	/*!< in: guessed block */
	ib_uint64_t	modify_clock,/*!< in: modify clock value if mode is
				..._GUESS_ON_CLOCK */
	const char*	file,	/*!< in: file name */
	ulint		line,	/*!< in: line where called */
	mtr_t*		mtr);	/*!< in: mini-transaction */
/********************************************************************//**
This is used to get access to a known database page, when no waiting can be
done.
@return	TRUE if success */
UNIV_INTERN
ibool
buf_page_get_known_nowait(
/*======================*/
	ulint		rw_latch,/*!< in: RW_S_LATCH, RW_X_LATCH */
	buf_block_t*	block,	/*!< in: the known page */
	ulint		mode,	/*!< in: BUF_MAKE_YOUNG or BUF_KEEP_OLD */
	const char*	file,	/*!< in: file name */
	ulint		line,	/*!< in: line where called */
	mtr_t*		mtr);	/*!< in: mini-transaction */

/*******************************************************************//**
Given a tablespace id and page number tries to get that page. If the
page is not in the buffer pool it is not loaded and NULL is returned.
Suitable for using when holding the kernel mutex. */
UNIV_INTERN
const buf_block_t*
buf_page_try_get_func(
/*==================*/
	ulint		space_id,/*!< in: tablespace id */
	ulint		page_no,/*!< in: page number */
	const char*	file,	/*!< in: file name */
	ulint		line,	/*!< in: line where called */
	mtr_t*		mtr);	/*!< in: mini-transaction */

/** Tries to get a page. If the page is not in the buffer pool it is
not loaded.  Suitable for using when holding the kernel mutex.
@param space_id	in: tablespace id
@param page_no	in: page number
@param mtr	in: mini-transaction
@return		the page if in buffer pool, NULL if not */
#define buf_page_try_get(space_id, page_no, mtr)	\
	buf_page_try_get_func(space_id, page_no, __FILE__, __LINE__, mtr);

/********************************************************************//**
Get read access to a compressed page (usually of type
FIL_PAGE_TYPE_ZBLOB or FIL_PAGE_TYPE_ZBLOB2).
The page must be released with buf_page_release_zip().
NOTE: the page is not protected by any latch.  Mutual exclusion has to
be implemented at a higher level.  In other words, all possible
accesses to a given page through this function must be protected by
the same set of mutexes or latches.
@return	pointer to the block, or NULL if not compressed */
UNIV_INTERN
buf_page_t*
buf_page_get_zip(
/*=============*/
	ulint		space,	/*!< in: space id */
	ulint		zip_size,/*!< in: compressed page size */
	ulint		offset);/*!< in: page number */
/********************************************************************//**
This is the general function used to get access to a database page.
@return	pointer to the block or NULL */
UNIV_INTERN
buf_block_t*
buf_page_get_gen(
/*=============*/
	ulint		space,	/*!< in: space id */
	ulint		zip_size,/*!< in: compressed page size in bytes
				or 0 for uncompressed pages */
	ulint		offset,	/*!< in: page number */
	ulint		rw_latch,/*!< in: RW_S_LATCH, RW_X_LATCH, RW_NO_LATCH */
	buf_block_t*	guess,	/*!< in: guessed block or NULL */
	ulint		mode,	/*!< in: BUF_GET, BUF_GET_IF_IN_POOL,
				BUF_PEEK_IF_IN_POOL, BUF_GET_NO_LATCH or
				BUF_GET_IF_IN_POOL_OR_WATCH */
	const char*	file,	/*!< in: file name */
	ulint		line,	/*!< in: line where called */
	mtr_t*		mtr);	/*!< in: mini-transaction */
/********************************************************************//**
Initializes a page to the buffer buf_pool. The page is usually not read
from a file even if it cannot be found in the buffer buf_pool. This is one
of the functions which perform to a block a state transition NOT_USED =>
FILE_PAGE (the other is buf_page_get_gen).
@return	pointer to the block, page bufferfixed */
UNIV_INTERN
buf_block_t*
buf_page_create(
/*============*/
	ulint	space,	/*!< in: space id */
	ulint	offset,	/*!< in: offset of the page within space in units of
			a page */
	ulint	zip_size,/*!< in: compressed page size, or 0 */
	mtr_t*	mtr);	/*!< in: mini-transaction handle */
#else /* !UNIV_HOTBACKUP */
/********************************************************************//**
Inits a page to the buffer buf_pool, for use in ibbackup --restore. */
UNIV_INTERN
void
buf_page_init_for_backup_restore(
/*=============================*/
	ulint		space,	/*!< in: space id */
	ulint		offset,	/*!< in: offset of the page within space
				in units of a page */
	ulint		zip_size,/*!< in: compressed page size in bytes
				or 0 for uncompressed pages */
	buf_block_t*	block);	/*!< in: block to init */
#endif /* !UNIV_HOTBACKUP */

#ifndef UNIV_HOTBACKUP
/********************************************************************//**
Releases a compressed-only page acquired with buf_page_get_zip(). */
UNIV_INLINE
void
buf_page_release_zip(
/*=================*/
	buf_page_t*	bpage);		/*!< in: buffer block */
/********************************************************************//**
Decrements the bufferfix count of a buffer control block and releases
a latch, if specified. */
UNIV_INLINE
void
buf_page_release(
/*=============*/
	buf_block_t*	block,		/*!< in: buffer block */
	ulint		rw_latch);	/*!< in: RW_S_LATCH, RW_X_LATCH,
					RW_NO_LATCH */
/********************************************************************//**
Moves a page to the start of the buffer pool LRU list. This high-level
function can be used to prevent an important page from slipping out of
the buffer pool. */
UNIV_INTERN
void
buf_page_make_young(
/*================*/
	buf_page_t*	bpage);	/*!< in: buffer block of a file page */
/********************************************************************//**
Returns TRUE if the page can be found in the buffer pool hash table.

NOTE that it is possible that the page is not yet read from disk,
though.

@return	TRUE if found in the page hash table */
UNIV_INLINE
ibool
buf_page_peek(
/*==========*/
	ulint	space,	/*!< in: space id */
	ulint	offset);/*!< in: page number */
/********************************************************************//**
Resets the check_index_page_at_flush field of a page if found in the buffer
pool. */
UNIV_INTERN
void
buf_reset_check_index_page_at_flush(
/*================================*/
	ulint	space,	/*!< in: space id */
	ulint	offset);/*!< in: page number */
#if defined UNIV_DEBUG_FILE_ACCESSES || defined UNIV_DEBUG
/********************************************************************//**
Sets file_page_was_freed TRUE if the page is found in the buffer pool.
This function should be called when we free a file page and want the
debug version to check that it is not accessed any more unless
reallocated.
@return	control block if found in page hash table, otherwise NULL */
UNIV_INTERN
buf_page_t*
buf_page_set_file_page_was_freed(
/*=============================*/
	ulint	space,	/*!< in: space id */
	ulint	offset);/*!< in: page number */
/********************************************************************//**
Sets file_page_was_freed FALSE if the page is found in the buffer pool.
This function should be called when we free a file page and want the
debug version to check that it is not accessed any more unless
reallocated.
@return	control block if found in page hash table, otherwise NULL */
UNIV_INTERN
buf_page_t*
buf_page_reset_file_page_was_freed(
/*===============================*/
	ulint	space,	/*!< in: space id */
	ulint	offset);	/*!< in: page number */
#endif /* UNIV_DEBUG_FILE_ACCESSES || UNIV_DEBUG */
/********************************************************************//**
Reads the freed_page_clock of a buffer block.
@return	freed_page_clock */
UNIV_INLINE
ulint
buf_page_get_freed_page_clock(
/*==========================*/
	const buf_page_t*	bpage)	/*!< in: block */
	__attribute__((pure));
/********************************************************************//**
Reads the freed_page_clock of a buffer block.
@return	freed_page_clock */
UNIV_INLINE
ulint
buf_block_get_freed_page_clock(
/*===========================*/
	const buf_block_t*	block)	/*!< in: block */
	__attribute__((pure));

/********************************************************************//**
Tells if a block is still close enough to the MRU end of the LRU list
meaning that it is not in danger of getting evicted and also implying
that it has been accessed recently.
Note that this is for heuristics only and does not reserve buffer pool
mutex.
@return	TRUE if block is close to MRU end of LRU */
UNIV_INLINE
ibool
buf_page_peek_if_young(
/*===================*/
	const buf_page_t*	bpage);	/*!< in: block */
/********************************************************************//**
Recommends a move of a block to the start of the LRU list if there is danger
of dropping from the buffer pool. NOTE: does not reserve the buffer pool
mutex.
@return	TRUE if should be made younger */
UNIV_INLINE
ibool
buf_page_peek_if_too_old(
/*=====================*/
	const buf_page_t*	bpage);	/*!< in: block to make younger */
/********************************************************************//**
Gets the youngest modification log sequence number for a frame.
Returns zero if not file page or no modification occurred yet.
@return	newest modification to page */
UNIV_INLINE
ib_uint64_t
buf_page_get_newest_modification(
/*=============================*/
	const buf_page_t*	bpage);	/*!< in: block containing the
					page frame */
/********************************************************************//**
Increments the modify clock of a frame by 1. The caller must (1) own the
buf_pool->mutex and block bufferfix count has to be zero, (2) or own an x-lock
on the block. */
UNIV_INLINE
void
buf_block_modify_clock_inc(
/*=======================*/
	buf_block_t*	block);	/*!< in: block */
/********************************************************************//**
Returns the value of the modify clock. The caller must have an s-lock
or x-lock on the block.
@return	value */
UNIV_INLINE
ib_uint64_t
buf_block_get_modify_clock(
/*=======================*/
	buf_block_t*	block);	/*!< in: block */
/*******************************************************************//**
Increments the bufferfix count. */
UNIV_INLINE
void
buf_block_buf_fix_inc_func(
/*=======================*/
# ifdef UNIV_SYNC_DEBUG
	const char*	file,	/*!< in: file name */
	ulint		line,	/*!< in: line */
# endif /* UNIV_SYNC_DEBUG */
	buf_block_t*	block)	/*!< in/out: block to bufferfix */
	__attribute__((nonnull));
# ifdef UNIV_SYNC_DEBUG
/** Increments the bufferfix count.
@param b	in/out: block to bufferfix
@param f	in: file name where requested
@param l	in: line number where requested */
# define buf_block_buf_fix_inc(b,f,l) buf_block_buf_fix_inc_func(f,l,b)
# else /* UNIV_SYNC_DEBUG */
/** Increments the bufferfix count.
@param b	in/out: block to bufferfix
@param f	in: file name where requested
@param l	in: line number where requested */
# define buf_block_buf_fix_inc(b,f,l) buf_block_buf_fix_inc_func(b)
# endif /* UNIV_SYNC_DEBUG */
#else /* !UNIV_HOTBACKUP */
# define buf_block_modify_clock_inc(block) ((void) 0)
#endif /* !UNIV_HOTBACKUP */
/********************************************************************//**
Calculates a page checksum which is stored to the page when it is written
to a file. Note that we must be careful to calculate the same value
on 32-bit and 64-bit architectures.
@return	checksum */
UNIV_INTERN
ulint
buf_calc_page_new_checksum(
/*=======================*/
	const byte*	page);	/*!< in: buffer page */
UNIV_INTERN
ulint
buf_calc_page_new_checksum_32(
/*==========================*/
	const byte*	page);	/*!< in: buffer page */
/********************************************************************//**
In versions < 4.0.14 and < 4.1.1 there was a bug that the checksum only
looked at the first few bytes of the page. This calculates that old
checksum.
NOTE: we must first store the new formula checksum to
FIL_PAGE_SPACE_OR_CHKSUM before calculating and storing this old checksum
because this takes that field as an input!
@return	checksum */
UNIV_INTERN
ulint
buf_calc_page_old_checksum(
/*=======================*/
	const byte*	 page);	/*!< in: buffer page */
/********************************************************************//**
Checks if a page is corrupt.
@return	TRUE if corrupted */
UNIV_INTERN
ibool
buf_page_is_corrupted(
/*==================*/
	ibool		check_lsn,	/*!< in: TRUE if we need to check
					and complain about the LSN */
	const byte*	read_buf,	/*!< in: a database page */
	ulint		zip_size)	/*!< in: size of compressed page;
					0 for uncompressed pages */
	__attribute__((warn_unused_result));
#ifndef UNIV_HOTBACKUP
/**********************************************************************//**
Gets the space id, page offset, and byte offset within page of a
pointer pointing to a buffer frame containing a file page. */
UNIV_INLINE
void
buf_ptr_get_fsp_addr(
/*=================*/
	const void*	ptr,	/*!< in: pointer to a buffer frame */
	ulint*		space,	/*!< out: space id */
	fil_addr_t*	addr);	/*!< out: page offset and byte offset */
/**********************************************************************//**
Gets the hash value of a block. 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 */
	__attribute__((pure));
#ifdef UNIV_DEBUG
/*********************************************************************//**
Finds a block in the buffer pool that points to a
given compressed page.
@return	buffer block pointing to the compressed page, or NULL */
UNIV_INTERN
buf_block_t*
buf_pool_contains_zip(
/*==================*/
	buf_pool_t*	buf_pool,	/*!< in: buffer pool instance */
	const void*	data);		/*!< in: pointer to compressed page */
#endif /* UNIV_DEBUG */
#if defined UNIV_DEBUG || defined UNIV_BUF_DEBUG
/*********************************************************************//**
Validates the buffer pool data structure.
@return	TRUE */
UNIV_INTERN
ibool
buf_validate(void);
/*==============*/
#endif /* UNIV_DEBUG || UNIV_BUF_DEBUG */
#if defined UNIV_DEBUG_PRINT || defined UNIV_DEBUG || defined UNIV_BUF_DEBUG
/*********************************************************************//**
Prints info of the buffer pool data structure. */
UNIV_INTERN
void
buf_print(void);
/*============*/
#endif /* UNIV_DEBUG_PRINT || UNIV_DEBUG || UNIV_BUF_DEBUG */
#endif /* !UNIV_HOTBACKUP */
enum buf_page_print_flags {
	/** Do not crash at the end of buf_page_print(). */
	BUF_PAGE_PRINT_NO_CRASH	= 1,
	/** Do not print the full page dump. */
	BUF_PAGE_PRINT_NO_FULL = 2
};

/********************************************************************//**
Prints a page to stderr. */
UNIV_INTERN
void
buf_page_print(
/*===========*/
	const byte*	read_buf,	/*!< in: a database page */
	ulint		zip_size,	/*!< in: compressed page size, or
					0 for uncompressed pages */
	ulint		flags)		/*!< in: 0 or
					BUF_PAGE_PRINT_NO_CRASH or
					BUF_PAGE_PRINT_NO_FULL */
	__attribute__((nonnull));
/********************************************************************//**
Decompress a block.
@return	TRUE if successful */
UNIV_INTERN
ibool
buf_zip_decompress(
/*===============*/
	buf_block_t*	block,	/*!< in/out: block */
	ibool		check);	/*!< in: TRUE=verify the page checksum */
#ifndef UNIV_HOTBACKUP
#ifdef UNIV_DEBUG
/*********************************************************************//**
Returns the number of latched pages in the buffer pool.
@return	number of latched pages */
UNIV_INTERN
ulint
buf_get_latched_pages_number(void);
/*==============================*/
#endif /* UNIV_DEBUG */
/*********************************************************************//**
Returns the number of pending buf pool ios.
@return	number of pending I/O operations */
UNIV_INTERN
ulint
buf_get_n_pending_ios(void);
/*=======================*/
/*********************************************************************//**
Prints info of the buffer i/o. */
UNIV_INTERN
void
buf_print_io(
/*=========*/
	FILE*	file);	/*!< in: file where to print */
/*******************************************************************//**
Collect buffer pool stats information for a buffer pool. Also
record aggregated stats if there are more than one buffer pool
in the server */
UNIV_INTERN
void
buf_stats_get_pool_info(
/*====================*/
	buf_pool_t*		buf_pool,	/*!< in: buffer pool */
	ulint			pool_id,	/*!< in: buffer pool ID */
	buf_pool_info_t*	all_pool_info);	/*!< in/out: buffer pool info
						to fill */
/*********************************************************************//**
Returns the ratio in percents of modified pages in the buffer pool /
database pages in the buffer pool.
@return	modified page percentage ratio */
UNIV_INTERN
ulint
buf_get_modified_ratio_pct(void);
/*============================*/
/**********************************************************************//**
Refreshes the statistics used to print per-second averages. */
UNIV_INTERN
void
buf_refresh_io_stats(
/*=================*/
	buf_pool_t*	buf_pool);	/*!< buffer pool instance */
/**********************************************************************//**
Refreshes the statistics used to print per-second averages. */
UNIV_INTERN
void
buf_refresh_io_stats_all(void);
/*=================*/
/*********************************************************************//**
Asserts that all file pages in the buffer are in a replaceable state.
@return	TRUE */
UNIV_INTERN
ibool
buf_all_freed(void);
/*===============*/
/*********************************************************************//**
Checks that there currently are no pending i/o-operations for the buffer
pool.
@return	number of pending i/o operations */
UNIV_INTERN
ulint
buf_pool_check_num_pending_io(void);
/*===============================*/
/*********************************************************************//**
Invalidates the file pages in the buffer pool when an archive recovery is
completed. All the file pages buffered must be in a replaceable state when
this function is called: not latched and not modified. */
UNIV_INTERN
void
buf_pool_invalidate(void);
/*=====================*/
#endif /* !UNIV_HOTBACKUP */

/*========================================================================
--------------------------- LOWER LEVEL ROUTINES -------------------------
=========================================================================*/

#ifdef UNIV_SYNC_DEBUG
/*********************************************************************//**
Adds latch level info for the rw-lock protecting the buffer frame. This
should be called in the debug version after a successful latching of a
page if we know the latching order level of the acquired latch. */
UNIV_INLINE
void
buf_block_dbg_add_level(
/*====================*/
	buf_block_t*	block,	/*!< in: buffer page
				where we have acquired latch */
	ulint		level);	/*!< in: latching order level */
#else /* UNIV_SYNC_DEBUG */
# define buf_block_dbg_add_level(block, level) /* nothing */
#endif /* UNIV_SYNC_DEBUG */
/*********************************************************************//**
Gets the state of a block.
@return	state */
UNIV_INLINE
enum buf_page_state
buf_page_get_state(
/*===============*/
	const buf_page_t*	bpage);	/*!< in: pointer to the control block */
/*********************************************************************//**
Gets the state of a block.
@return	state */
UNIV_INLINE
enum buf_page_state
buf_block_get_state(
/*================*/
	const buf_block_t*	block)	/*!< in: pointer to the control block */
	__attribute__((pure));
/*********************************************************************//**
Sets the state of a block. */
UNIV_INLINE
void
buf_page_set_state(
/*===============*/
	buf_page_t*		bpage,	/*!< in/out: pointer to control block */
	enum buf_page_state	state);	/*!< in: state */
/*********************************************************************//**
Sets the state of a block. */
UNIV_INLINE
void
buf_block_set_state(
/*================*/
	buf_block_t*		block,	/*!< in/out: pointer to control block */
	enum buf_page_state	state);	/*!< in: state */
/*********************************************************************//**
Determines if a block is mapped to a tablespace.
@return	TRUE if mapped */
UNIV_INLINE
ibool
buf_page_in_file(
/*=============*/
	const buf_page_t*	bpage)	/*!< in: pointer to control block */
	__attribute__((pure));
#ifndef UNIV_HOTBACKUP
/*********************************************************************//**
Determines if a block should be on unzip_LRU list.
@return	TRUE if block belongs to unzip_LRU */
UNIV_INLINE
ibool
buf_page_belongs_to_unzip_LRU(
/*==========================*/
	const buf_page_t*	bpage)	/*!< in: pointer to control block */
	__attribute__((pure));

/*********************************************************************//**
Gets the mutex of a block.
@return	pointer to mutex protecting bpage */
UNIV_INLINE
mutex_t*
buf_page_get_mutex(
/*===============*/
	const buf_page_t*	bpage)	/*!< in: pointer to control block */
	__attribute__((pure));

/*************************************************************************
Gets the mutex of a block and enter the mutex with consistency. */
UNIV_INLINE
mutex_t*
buf_page_get_mutex_enter(
/*=========================*/
	const buf_page_t*	bpage)	/*!< in: pointer to control block */
	__attribute__((pure));

/*********************************************************************//**
Get the flush type of a page.
@return	flush type */
UNIV_INLINE
enum buf_flush
buf_page_get_flush_type(
/*====================*/
	const buf_page_t*	bpage)	/*!< in: buffer page */
	__attribute__((pure));
/*********************************************************************//**
Set the flush type of a page. */
UNIV_INLINE
void
buf_page_set_flush_type(
/*====================*/
	buf_page_t*	bpage,		/*!< in: buffer page */
	enum buf_flush	flush_type);	/*!< in: flush type */
/*********************************************************************//**
Map a block to a file page. */
UNIV_INLINE
void
buf_block_set_file_page(
/*====================*/
	buf_block_t*		block,	/*!< in/out: pointer to control block */
	ulint			space,	/*!< in: tablespace id */
	ulint			page_no);/*!< in: page number */
/*********************************************************************//**
Gets the io_fix state of a block.  Requires that the block mutex is held.
@return	io_fix state */
UNIV_INLINE
enum buf_io_fix
buf_page_get_io_fix(
/*================*/
	const buf_page_t*	bpage)	/*!< in: pointer to the control block */
	__attribute__((pure));
/*********************************************************************//**
Gets the io_fix state of a block.  Does not assert that the block mutex is
held, to be used in the cases where it is safe not to hold it.
@return	io_fix state */
UNIV_INLINE
enum buf_io_fix
buf_page_get_io_fix_unlocked(
/*=========================*/
	const buf_page_t*	bpage)	/*!< in: pointer to the control block */
	__attribute__((pure));
/*********************************************************************//**
Gets the io_fix state of a block.  Requires that the block mutex is held.
@return	io_fix state */
UNIV_INLINE
enum buf_io_fix
buf_block_get_io_fix(
/*================*/
	const buf_block_t*	block)	/*!< in: pointer to the control block */
	__attribute__((pure));
/*********************************************************************//**
Gets the io_fix state of a block.  Does not assert that the block mutex is
held, to be used in the cases where it is safe not to hold it.
@return	io_fix state */
UNIV_INLINE
enum buf_io_fix
buf_block_get_io_fix_unlocked(
/*==========================*/
	const buf_block_t*	block)	/*!< in: pointer to the control block */
	__attribute__((pure));
/*********************************************************************//**
Sets the io_fix state of a block. */
UNIV_INLINE
void
buf_page_set_io_fix(
/*================*/
	buf_page_t*	bpage,	/*!< in/out: control block */
	enum buf_io_fix	io_fix);/*!< in: io_fix state */
/*********************************************************************//**
Sets the io_fix state of a block. */
UNIV_INLINE
void
buf_block_set_io_fix(
/*=================*/
	buf_block_t*	block,	/*!< in/out: control block */
	enum buf_io_fix	io_fix);/*!< in: io_fix state */
/*********************************************************************//**
Makes a block sticky. A sticky block implies that even after we release
the buf_pool->mutex and the block->mutex:
* it cannot be removed from the flush_list
* the block descriptor cannot be relocated
* it cannot be removed from the LRU list
Note that:
* the block can still change its position in the LRU list
* the next and previous pointers can change. */
UNIV_INLINE
void
buf_page_set_sticky(
/*================*/
	buf_page_t*	bpage);	/*!< in/out: control block */
/*********************************************************************//**
Removes stickiness of a block. */
UNIV_INLINE
void
buf_page_unset_sticky(
/*==================*/
	buf_page_t*	bpage);	/*!< in/out: control block */
/********************************************************************//**
Determine if a buffer block can be relocated in memory.  The block
can be dirty, but it must not be I/O-fixed or bufferfixed. */
UNIV_INLINE
ibool
buf_page_can_relocate(
/*==================*/
	const buf_page_t*	bpage)	/*!< control block being relocated */
	__attribute__((pure));

/*********************************************************************//**
Determine if a block has been flagged old.
@return	TRUE if old */
UNIV_INLINE
ibool
buf_page_is_old(
/*============*/
	const buf_page_t*	bpage)	/*!< in: control block */
	__attribute__((pure));
/*********************************************************************//**
Flag a block old. */
UNIV_INLINE
void
buf_page_set_old(
/*=============*/
	buf_page_t*	bpage,	/*!< in/out: control block */
	ibool		old);	/*!< in: old */
/*********************************************************************//**
Determine the time of first access of a block in the buffer pool.
@return	ut_time_ms() at the time of first access, 0 if not accessed */
UNIV_INLINE
unsigned
buf_page_is_accessed(
/*=================*/
	const buf_page_t*	bpage)	/*!< in: control block */
	__attribute__((nonnull, pure));
/*********************************************************************//**
Flag a block accessed. */
UNIV_INLINE
void
buf_page_set_accessed(
/*==================*/
	buf_page_t*	bpage)		/*!< in/out: control block */
	__attribute__((nonnull));
/*********************************************************************//**
Gets the buf_block_t handle of a buffered file block if an uncompressed
page frame exists, or NULL. Note: even though bpage is not declared a
const we don't update its value. It is safe to make this pure.
@return	control block, or NULL */
UNIV_INLINE
buf_block_t*
buf_page_get_block(
/*===============*/
	buf_page_t*	bpage)	/*!< in: control block, or NULL */
	__attribute__((pure));
#endif /* !UNIV_HOTBACKUP */
#ifdef UNIV_DEBUG
/*********************************************************************//**
Gets a pointer to the memory frame of a block.
@return	pointer to the frame */
UNIV_INLINE
buf_frame_t*
buf_block_get_frame(
/*================*/
	const buf_block_t*	block)	/*!< in: pointer to the control block */
	__attribute__((pure));

/*********************************************************************//**
Gets a pointer to the memory frame of a block, where block is known not to be
NULL.
@return	pointer to the frame */
UNIV_INLINE
buf_frame_t*
buf_nonnull_block_get_frame(
	const buf_block_t*	block)	/*!< in: pointer to the control block */
	__attribute__((pure));

#else /* UNIV_DEBUG */
# define buf_block_get_frame(block) (block ? (block)->frame : 0)
# define buf_nonnull_block_get_frame(block) ((block)->frame)
#endif /* UNIV_DEBUG */
/*********************************************************************//**
Gets the space id of a block.
@return	space id */
UNIV_INLINE
ulint
buf_page_get_space(
/*===============*/
	const buf_page_t*	bpage)	/*!< in: pointer to the control block */
	__attribute__((pure));
/*********************************************************************//**
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 */
	__attribute__((pure));
/*********************************************************************//**
Gets the page number of a block.
@return	page number */
UNIV_INLINE
ulint
buf_page_get_page_no(
/*=================*/
	const buf_page_t*	bpage)	/*!< in: pointer to the control block */
	__attribute__((pure));
/*********************************************************************//**
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 */
	__attribute__((pure));
/*********************************************************************//**
Gets the compressed page size of a block.
@return	compressed page size, or 0 */
UNIV_INLINE
ulint
buf_page_get_zip_size(
/*==================*/
	const buf_page_t*	bpage)	/*!< in: pointer to the control block */
	__attribute__((pure));
/*********************************************************************//**
Gets the compressed page size of a block.
@return	compressed page size, or 0 */
UNIV_INLINE
ulint
buf_block_get_zip_size(
/*===================*/
	const buf_block_t*	block)	/*!< in: pointer to the control block */
	__attribute__((pure));
/*********************************************************************//**
Gets the compressed page descriptor corresponding to an uncompressed page
if applicable. */
#define buf_block_get_page_zip(block) \
	(UNIV_LIKELY_NULL((block)->page.zip.data) ? &(block)->page.zip : NULL)
#ifndef UNIV_HOTBACKUP
/*******************************************************************//**
Gets the block to whose frame the pointer is pointing to.
@return	pointer to block, never NULL */
UNIV_INTERN
buf_block_t*
buf_block_align(
/*============*/
	const byte*	ptr);	/*!< in: pointer to a frame */
/********************************************************************//**
Find out if a pointer belongs to a buf_block_t. It can be a pointer to
the buf_block_t itself or a member of it
@return	TRUE if ptr belongs to a buf_block_t struct */
UNIV_INTERN
ibool
buf_pointer_is_block_field(
/*=======================*/
	const void*		ptr);	/*!< in: pointer not
					dereferenced */
/** Find out if a pointer corresponds to a buf_block_t::mutex.
@param m	in: mutex candidate
@return		TRUE if m is a buf_block_t::mutex */
#define buf_pool_is_block_mutex(m)			\
	buf_pointer_is_block_field((const void*)(m))
/** Find out if a pointer corresponds to a buf_block_t::lock.
@param l	in: rw-lock candidate
@return		TRUE if l is a buf_block_t::lock */
#define buf_pool_is_block_lock(l)			\
	buf_pointer_is_block_field((const void*)(l))

#if defined UNIV_DEBUG || defined UNIV_ZIP_DEBUG
/*********************************************************************//**
Gets the compressed page descriptor corresponding to an uncompressed page
if applicable.
@return	compressed page descriptor, or NULL */
UNIV_INLINE
const page_zip_des_t*
buf_frame_get_page_zip(
/*===================*/
	const byte*	ptr);	/*!< in: pointer to the page */
#endif /* UNIV_DEBUG || UNIV_ZIP_DEBUG */
/********************************************************************//**
Function which inits a page for read to the buffer buf_pool. If the page is
(1) already in buf_pool, or
(2) if we specify to read only ibuf pages and the page is not an ibuf page, or
(3) if the space is deleted or being deleted,
then this function does nothing.
Sets the io_fix flag to BUF_IO_READ and sets a non-recursive exclusive lock
on the buffer frame. The io-handler must take care that the flag is cleared
and the lock released later.
@return	pointer to the block or NULL */
UNIV_INTERN
buf_page_t*
buf_page_init_for_read(
/*===================*/
	ulint*		err,	/*!< out: DB_SUCCESS or DB_TABLESPACE_DELETED */
	ulint		mode,	/*!< in: BUF_READ_IBUF_PAGES_ONLY, ... */
	ulint		space,	/*!< in: space id */
	ulint		zip_size,/*!< in: compressed page size, or 0 */
	ibool		unzip,	/*!< in: TRUE=request uncompressed page */
	ib_int64_t	tablespace_version,/*!< in: prevents reading from a wrong
				version of the tablespace in case we have done
				DISCARD + IMPORT */
	ulint		offset);/*!< in: page number */
/********************************************************************//**
Completes an asynchronous read or write request of a file page to or from
the buffer pool.
@return TRUE if successful */
UNIV_INTERN
ibool
buf_page_io_complete(
/*=================*/
	buf_page_t*	bpage);	/*!< in: pointer to the block in question */
/********************************************************************//**
Calculates a folded value of a file page address to use in the page hash
table.
@return	the folded value */
UNIV_INLINE
ulint
buf_page_address_fold(
/*==================*/
	ulint	space,	/*!< in: space id */
	ulint	offset)	/*!< in: offset of the page within space */
	__attribute__((const));
/********************************************************************//**
Calculates the index of a buffer pool to the buf_pool[] array.
@return	the position of the buffer pool in buf_pool[] */
UNIV_INLINE
ulint
buf_pool_index(
/*===========*/
	const buf_pool_t*	buf_pool)	/*!< in: buffer pool */
	__attribute__((nonnull, const));
/********************************************************************//**
*/
UNIV_INTERN
buf_block_t*
buf_page_from_array(
/*================*/
	buf_pool_t*	buf_pool,
	ulint		n_block);
/******************************************************************//**
Returns the buffer pool instance given a page instance
@return buf_pool */
UNIV_INLINE
buf_pool_t*
buf_pool_from_bpage(
/*================*/
	const buf_page_t*	bpage); /*!< in: buffer pool page */
/******************************************************************//**
Returns the buffer pool instance given a block instance
@return buf_pool */
UNIV_INLINE
buf_pool_t*
buf_pool_from_block(
/*================*/
	const buf_block_t*	block); /*!< in: block */
/******************************************************************//**
Returns the buffer pool instance given space and offset of page
@return buffer pool */
UNIV_INLINE
buf_pool_t*
buf_pool_get(
/*==========*/
	ulint	space,	/*!< in: space id */
	ulint	offset);/*!< in: offset of the page within space */
/******************************************************************//**
Returns the buffer pool instance given its array index
@return buffer pool */
UNIV_INLINE
buf_pool_t*
buf_pool_from_array(
/*================*/
	ulint	index);		/*!< in: array index to get
				buffer pool instance from */
/******************************************************************//**
Returns the control block of a file page, NULL if not found.
@return	block, NULL if not found */
UNIV_INLINE
buf_page_t*
buf_page_hash_get_low(
/*==================*/
	buf_pool_t*	buf_pool,	/*!< buffer pool instance */
	ulint		space,		/*!< in: space id */
	ulint		offset,		/*!< in: offset of the page
					within space */
	ulint		fold);		/*!< in: buf_page_address_fold(
					space, offset) */
/******************************************************************//**
Returns the control block of a file page, NULL if not found.
@return	block, NULL if not found or not a real control block */
UNIV_INLINE
buf_page_t*
buf_page_hash_get(
/*==============*/
	buf_pool_t*	buf_pool,	/*!< in: buffer pool instance */
	ulint		space,		/*!< in: space id */
	ulint		offset);	/*!< in: offset of the page
					within space */
/******************************************************************//**
Returns the control block of a file page, NULL if not found
or an uncompressed page frame does not exist.
@return	block, NULL if not found */
UNIV_INLINE
buf_block_t*
buf_block_hash_get(
/*===============*/
	buf_pool_t*	buf_pool,	/*!< in: buffer pool instance */
	ulint		space,		/*!< in: space id */
	ulint		offset);	/*!< in: offset of the page
					within space */
/*********************************************************************//**
Gets the current length of the free list of buffer blocks.
@return	length of the free list */
UNIV_INTERN
ulint
buf_get_free_list_len(void);
/*=======================*/

/********************************************************************//**
Determine if a block is a sentinel for a buffer pool watch.
@return	TRUE if a sentinel for a buffer pool watch, FALSE if not */
UNIV_INTERN
ibool
buf_pool_watch_is_sentinel(
/*=======================*/
	buf_pool_t*		buf_pool,	/*!< buffer pool instance */
	const buf_page_t*	bpage)		/*!< in: block */
	__attribute__((nonnull, warn_unused_result));
/****************************************************************//**
Add watch for the given page to be read in. Caller must have the buffer pool
@return NULL if watch set, block if the page is in the buffer pool */
UNIV_INTERN
buf_page_t*
buf_pool_watch_set(
/*===============*/
	ulint	space,	/*!< in: space id */
	ulint	offset,	/*!< in: page number */
	ulint	fold)	/*!< in: buf_page_address_fold(space, offset) */
	__attribute__((warn_unused_result));
/****************************************************************//**
Stop watching if the page has been read in.
buf_pool_watch_set(space,offset) must have returned NULL before. */
UNIV_INTERN
void
buf_pool_watch_unset(
/*=================*/
	ulint	space,	/*!< in: space id */
	ulint	offset);/*!< in: page number */
/****************************************************************//**
Check if the page has been read in.
This may only be called after buf_pool_watch_set(space,offset)
has returned NULL and before invoking buf_pool_watch_unset(space,offset).
@return	FALSE if the given page was not read in, TRUE if it was */
UNIV_INTERN
ibool
buf_pool_watch_occurred(
/*====================*/
	ulint	space,	/*!< in: space id */
	ulint	offset)	/*!< in: page number */
	__attribute__((warn_unused_result));
/********************************************************************//**
Get total buffer pool statistics. */
UNIV_INTERN
void
buf_get_total_list_len(
/*===================*/
	ulint*		LRU_len,	/*!< out: length of all LRU lists */
	ulint*		free_len,	/*!< out: length of all free lists */
	ulint*		flush_list_len);/*!< out: length of all flush lists */
/********************************************************************//**
Get total list size in bytes from all buffer pools. */
UNIV_INTERN
void
buf_get_total_list_size_in_bytes(
/*=============================*/
	buf_pools_list_size_t*	buf_pools_list_size);	/*!< out: list sizes
							in all buffer pools */
/********************************************************************//**
Get total buffer pool statistics. */
UNIV_INTERN
void
buf_get_total_stat(
/*===============*/
	buf_pool_stat_t*tot_stat);	/*!< out: buffer pool stats */
/*********************************************************************//**
Get the nth chunk's buffer block in the specified buffer pool.
@return the nth chunk's buffer block. */
UNIV_INLINE
buf_block_t*
buf_get_nth_chunk_block(
/*====================*/
	const buf_pool_t* buf_pool,	/*!< in: buffer pool instance */
	ulint		n,		/*!< in: nth chunk in the buffer pool */
	ulint*		chunk_size);	/*!< in: chunk size */

#endif /* !UNIV_HOTBACKUP */

/** The common buffer control block structure
for compressed and uncompressed frames */

/** Number of bits used for buffer page states. */
#define BUF_PAGE_STATE_BITS	3

struct buf_page_struct{
	/** @name General fields
	None of these bit-fields must be modified without holding
	buf_page_get_mutex() [buf_block_struct::mutex or
	buf_pool->zip_mutex], since they can be stored in the same
	machine word.  Some of these fields are additionally protected
	by buf_pool->mutex. */
	/* @{ */

	unsigned	space:32;	/*!< tablespace id; also protected
					by buf_pool->mutex. */
	unsigned	offset:32;	/*!< page number; also protected
					by buf_pool->mutex. */

	unsigned	state:BUF_PAGE_STATE_BITS;
					/*!< state of the control block; also
					protected by buf_pool->mutex.
					State transitions from
					BUF_BLOCK_READY_FOR_USE to
					BUF_BLOCK_MEMORY need not be
					protected by buf_page_get_mutex().
					@see enum buf_page_state */
#ifndef UNIV_HOTBACKUP
	unsigned	flush_type:2;	/*!< if this block is currently being
					flushed to disk, this tells the
					flush_type.
					@see enum buf_flush */
	unsigned	io_fix:2;	/*!< type of pending I/O operation;
					also protected by buf_pool->mutex
					@see enum buf_io_fix */
	unsigned	buf_fix_count:19;/*!< count of how manyfold this block
					is currently bufferfixed */
	unsigned	buf_pool_index:6;/*!< index number of the buffer pool
					that this block belongs to */
# if MAX_BUFFER_POOLS > 64
#  error "MAX_BUFFER_POOLS > 64; redefine buf_pool_index:6"
# endif
	/* @} */
#endif /* !UNIV_HOTBACKUP */
	page_zip_des_t	zip;		/*!< compressed page; zip.data
					(but not the data it points to) is
					also protected by buf_pool->mutex;
					state == BUF_BLOCK_ZIP_PAGE and
					zip.data == NULL means an active
					buf_pool->watch */
#ifndef UNIV_HOTBACKUP
	buf_page_t*	hash;		/*!< node used in chaining to
					buf_pool->page_hash or
					buf_pool->zip_hash */
#ifdef UNIV_DEBUG
	ibool		in_page_hash;	/*!< TRUE if in buf_pool->page_hash */
	ibool		in_zip_hash;	/*!< TRUE if in buf_pool->zip_hash */
#endif /* UNIV_DEBUG */

	/** @name Page flushing fields
	All these are protected by buf_pool->mutex. */
	/* @{ */

	/* UT_LIST_NODE_T(buf_page_t) list; */
					/*!< based on state, this is a
					list node, protected either by
					buf_pool->mutex or by
					buf_pool->flush_list_mutex,
					in one of the following lists in
					buf_pool:

					- BUF_BLOCK_NOT_USED:	free
					- BUF_BLOCK_FILE_PAGE:	flush_list
					- BUF_BLOCK_ZIP_DIRTY:	flush_list
					- BUF_BLOCK_ZIP_PAGE:	zip_clean
					- BUF_BLOCK_ZIP_FREE:	zip_free[]

					If bpage is part of flush_list
					then the node pointers are
					covered by buf_pool->flush_list_mutex.
					Otherwise these pointers are
					protected by buf_pool->mutex.

					The contents of the list node
					is undefined if !in_flush_list
					&& state == BUF_BLOCK_FILE_PAGE,
					or if state is one of
					BUF_BLOCK_MEMORY,
					BUF_BLOCK_REMOVE_HASH or
					BUF_BLOCK_READY_IN_USE. */

	/* resplit for optimistic use */
	UT_LIST_NODE_T(buf_page_t) free;
	UT_LIST_NODE_T(buf_page_t) flush_list;
	UT_LIST_NODE_T(buf_page_t) zip_list; /* zip_clean or zip_free[] */
#ifdef UNIV_DEBUG
	ibool		in_flush_list;	/*!< TRUE if in buf_pool->flush_list;
					when buf_pool->flush_list_mutex is
					free, the following should hold:
					in_flush_list
					== (state == BUF_BLOCK_FILE_PAGE
					    || state == BUF_BLOCK_ZIP_DIRTY)
					Writes to this field must be
					covered by both block->mutex
					and buf_pool->flush_list_mutex. Hence
					reads can happen while holding
					any one of the two mutexes */
	ibool		in_free_list;	/*!< TRUE if in buf_pool->free; when
					buf_pool->mutex is free, the following
					should hold: in_free_list
					== (state == BUF_BLOCK_NOT_USED) */
#endif /* UNIV_DEBUG */
	ib_uint64_t	newest_modification;
					/*!< log sequence number of
					the youngest modification to
					this block, zero if not
					modified. Protected by block
					mutex */
	ib_uint64_t	oldest_modification;
					/*!< log sequence number of
					the START of the log entry
					written of the oldest
					modification to this block
					which has not yet been flushed
					on disk; zero if all
					modifications are on disk.
					Writes to this field must be
					covered by both block->mutex
					and buf_pool->flush_list_mutex. Hence
					reads can happen while holding
					any one of the two mutexes */
	/* @} */
	/** @name LRU replacement algorithm fields
	These fields are protected by buf_pool->mutex only (not
	buf_pool->zip_mutex or buf_block_struct::mutex). */
	/* @{ */

	UT_LIST_NODE_T(buf_page_t) LRU;
					/*!< node of the LRU list */
//#ifdef UNIV_DEBUG
	ibool		in_LRU_list;	/*!< TRUE if the page is in
					the LRU list; used in
					debugging */
//#endif /* UNIV_DEBUG */
	unsigned	old:1;		/*!< TRUE if the block is in the old
					blocks in buf_pool->LRU_old */
	unsigned	freed_page_clock:31;/*!< the value of
					buf_pool->freed_page_clock
					when this block was the last
					time put to the head of the
					LRU list; a thread is allowed
					to read this for heuristic
					purposes without holding any
					mutex or latch */
	/* @} */
	unsigned	access_time;	/*!< time of first access, or
					0 if the block was never accessed
					in the buffer pool. Protected by
					block mutex */
	ibool		is_corrupt;
# if defined UNIV_DEBUG_FILE_ACCESSES || defined UNIV_DEBUG
	ibool		file_page_was_freed;
					/*!< this is set to TRUE when fsp
					frees a page in buffer pool */
# endif /* UNIV_DEBUG_FILE_ACCESSES || UNIV_DEBUG */
#endif /* !UNIV_HOTBACKUP */
};

/** The buffer control block structure */

struct buf_block_struct{

	/** @name General fields */
	/* @{ */

	buf_page_t	page;		/*!< page information; this must
					be the first field, so that
					buf_pool->page_hash can point
					to buf_page_t or buf_block_t */
	byte*		frame;		/*!< pointer to buffer frame which
					is of size UNIV_PAGE_SIZE, and
					aligned to an address divisible by
					UNIV_PAGE_SIZE */
#ifndef UNIV_HOTBACKUP
	UT_LIST_NODE_T(buf_block_t) unzip_LRU;
					/*!< node of the decompressed LRU list;
					a block is in the unzip_LRU list
					if page.state == BUF_BLOCK_FILE_PAGE
					and page.zip.data != NULL */
//#ifdef UNIV_DEBUG
	ibool		in_unzip_LRU_list;/*!< TRUE if the page is in the
					decompressed LRU list;
					used in debugging */
//#endif /* UNIV_DEBUG */
	mutex_t		mutex;		/*!< mutex protecting this block:
					state (also protected by the buffer
					pool mutex), io_fix, buf_fix_count,
					and accessed; we introduce this new
					mutex in InnoDB-5.1 to relieve
					contention on the buffer pool mutex */
	rw_lock_t	lock;		/*!< read-write lock of the buffer
					frame */
	unsigned	lock_hash_val:32;/*!< hashed value of the page address
					in the record lock hash table;
					protected by buf_block_t::lock
					(or buf_block_t::mutex, buf_pool->mutex
				        in buf_page_get_gen(),
					buf_page_init_for_read()
					and buf_page_create()) */
	ibool		check_index_page_at_flush;
					/*!< TRUE if we know that this is
					an index page, and want the database
					to check its consistency before flush;
					note that there may be pages in the
					buffer pool which are index pages,
					but this flag is not set because
					we do not keep track of all pages;
					NOT protected by any mutex */
	/* @} */
	/** @name Optimistic search field */
	/* @{ */

	ib_uint64_t	modify_clock;	/*!< this clock is incremented every
					time a pointer to a record on the
					page may become obsolete; this is
					used in the optimistic cursor
					positioning: if the modify clock has
					not changed, we know that the pointer
					is still valid; this field may be
					changed if the thread (1) owns the
					pool mutex and the page is not
					bufferfixed, or (2) the thread has an
					x-latch on the block */
	/* @} */
	/** @name Hash search fields (unprotected)
	NOTE that these fields are NOT protected by any semaphore! */
	/* @{ */

	ulint		n_hash_helps;	/*!< counter which controls building
					of a new hash index for the page */
	ulint		n_fields;	/*!< recommended prefix length for hash
					search: number of full fields */
	ulint		n_bytes;	/*!< recommended prefix: number of bytes
					in an incomplete field */
	ibool		left_side;	/*!< TRUE or FALSE, depending on
					whether the leftmost record of several
					records with the same prefix should be
					indexed in the hash index */
	/* @} */

	/** @name Hash search fields
	These 5 fields may only be modified when we have
	an x-latch on btr_search_latch AND
	- we are holding an s-latch or x-latch on buf_block_struct::lock or
	- we know that buf_block_struct::buf_fix_count == 0.

	An exception to this is when we init or create a page
	in the buffer pool in buf0buf.c.

	Another exception is that assigning block->index = NULL
	is allowed whenever holding an x-latch on btr_search_latch. */

	/* @{ */

#if defined UNIV_AHI_DEBUG || defined UNIV_DEBUG
	ulint		n_pointers;	/*!< used in debugging: the number of
					pointers in the adaptive hash index
					pointing to this frame */
#endif /* UNIV_AHI_DEBUG || UNIV_DEBUG */
	unsigned	curr_n_fields:10;/*!< prefix length for hash indexing:
					number of full fields */
	unsigned	curr_n_bytes:15;/*!< number of bytes in hash
					indexing */
	unsigned	curr_left_side:1;/*!< TRUE or FALSE in hash indexing */
	dict_index_t*	index;		/*!< Index for which the
					adaptive hash index has been
					created, or NULL if the page
					does not exist in the
					index. Note that it does not
					guarantee that the index is
					complete, though: there may
					have been hash collisions,
					record deletions, etc. */
	/* @} */
# ifdef UNIV_SYNC_DEBUG
	/** @name Debug fields */
	/* @{ */
	rw_lock_t	debug_latch;	/*!< in the debug version, each thread
					which bufferfixes the block acquires
					an s-latch here; so we can use the
					debug utilities in sync0rw */
	/* @} */
# endif
#endif /* !UNIV_HOTBACKUP */
};

/** Check if a buf_block_t object is in a valid state
@param block	buffer block
@return		TRUE if valid */
#define buf_block_state_valid(block)				\
(buf_block_get_state(block) >= BUF_BLOCK_NOT_USED		\
 && (buf_block_get_state(block) <= BUF_BLOCK_REMOVE_HASH))

#ifndef UNIV_HOTBACKUP
/**********************************************************************//**
Compute the hash fold value for blocks in buf_pool->zip_hash. */
/* @{ */
#define BUF_POOL_ZIP_FOLD_PTR(ptr) ((ulint) (ptr) / UNIV_PAGE_SIZE)
#define BUF_POOL_ZIP_FOLD(b) BUF_POOL_ZIP_FOLD_PTR((b)->frame)
#define BUF_POOL_ZIP_FOLD_BPAGE(b) BUF_POOL_ZIP_FOLD((buf_block_t*) (b))
/* @} */

/** A chunk of buffers.  The buffer pool is allocated in chunks. */
struct buf_chunk_struct{
	ulint		mem_size;	/*!< allocated size of the chunk */
	ulint		size;		/*!< size of frames[] and blocks[] */
	void*		mem;		/*!< pointer to the memory area which
					was allocated for the frames */
	buf_block_t*	blocks;		/*!< array of buffer control blocks */
};

/** @brief The buffer pool statistics structure. */
struct buf_pool_stat_struct{
	ulint	n_page_gets;	/*!< number of page gets performed;
				also successful searches through
				the adaptive hash index are
				counted as page gets; this field
				is NOT protected by the buffer
				pool mutex */
	ulint	n_pages_read;	/*!< number read operations */
	ulint	n_pages_written;/*!< number write operations */
	ulint	n_pages_created;/*!< number of pages created
				in the pool with no read */
	ulint	n_ra_pages_read_rnd;/*!< number of pages read in
				as part of random read ahead */
	ulint	n_ra_pages_read;/*!< number of pages read in
				as part of read ahead */
	ulint	n_ra_pages_evicted;/*!< number of read ahead
				pages that are evicted without
				being accessed */
	ulint	n_pages_made_young; /*!< number of pages made young, in
				calls to buf_LRU_make_block_young() */
	ulint	n_pages_not_made_young; /*!< number of pages not made
				young because the first access
				was not long enough ago, in
				buf_page_peek_if_too_old() */
	ulint	LRU_bytes;	/*!< LRU size in bytes */
	ulint	flush_list_bytes;/*!< flush_list size in bytes */
};

/** Statistics of buddy blocks of a given size. */
struct buf_buddy_stat_struct {
	/** Number of blocks allocated from the buddy system. */
	ulint		used;
	/** Number of blocks relocated by the buddy system. */
	ib_uint64_t	relocated;
	/** Total duration of block relocations, in microseconds. */
	ib_uint64_t	relocated_usec;
};

/** @brief The buffer pool structure.

NOTE! The definition appears here only for other modules of this
directory (buf) to see it. Do not use from outside! */

struct buf_pool_struct{

	/** @name General fields */
	/* @{ */
	mutex_t		mutex;		/*!< Buffer pool mutex of this
					instance */
	mutex_t		zip_mutex;	/*!< Zip mutex of this buffer
					pool instance, protects compressed
					only pages (of type buf_page_t, not
					buf_block_t */
	mutex_t		LRU_list_mutex;
	rw_lock_t	page_hash_latch;
	mutex_t		free_list_mutex;
	mutex_t		zip_free_mutex;
	mutex_t		zip_hash_mutex;
	ulint		instance_no;	/*!< Array index of this buffer
					pool instance */
	ulint		old_pool_size;  /*!< Old pool size in bytes */
	ulint		curr_pool_size;	/*!< Current pool size in bytes */
	ulint		LRU_old_ratio;  /*!< Reserve this much of the buffer
					pool for "old" blocks */
#ifdef UNIV_DEBUG
	ulint		buddy_n_frames; /*!< Number of frames allocated from
					the buffer pool to the buddy system */
#endif
#if defined UNIV_DEBUG || defined UNIV_BUF_DEBUG
	ulint		mutex_exit_forbidden; /*!< Forbid release mutex */
#endif
	ulint		n_chunks;	/*!< number of buffer pool chunks */
	buf_chunk_t*	chunks;		/*!< buffer pool chunks */
	ulint		curr_size;	/*!< current pool size in pages */
	hash_table_t*	page_hash;	/*!< hash table of buf_page_t or
					buf_block_t file pages,
					buf_page_in_file() == TRUE,
					indexed by (space_id, offset) */
	hash_table_t*	zip_hash;	/*!< hash table of buf_block_t blocks
					whose frames are allocated to the
					zip buddy system,
					indexed by block->frame */
	ulint		n_pend_reads;	/*!< number of pending read
					operations */
	ulint		n_pend_unzip;	/*!< number of pending decompressions */

	time_t		last_printout_time;
					/*!< when buf_print_io was last time
					called */
	buf_buddy_stat_t buddy_stat[BUF_BUDDY_SIZES_MAX + 1];
					/*!< Statistics of buddy system,
					indexed by block size */
	buf_pool_stat_t	stat;		/*!< current statistics */
	buf_pool_stat_t	old_stat;	/*!< old statistics */

	/* @} */

	/** @name Page flushing algorithm fields */

	/* @{ */

	mutex_t		flush_list_mutex;/*!< mutex protecting the
					flush list access. This mutex
					protects flush_list, flush_rbt
					and bpage::list pointers when
					the bpage is on flush_list. It
					also protects writes to
					bpage::oldest_modification */
	UT_LIST_BASE_NODE_T(buf_page_t) flush_list;
					/*!< base node of the modified block
					list */
	ibool		init_flush[BUF_FLUSH_N_TYPES];
					/*!< this is TRUE when a flush of the
					given type is being initialized */
	ulint		n_flush[BUF_FLUSH_N_TYPES];
					/*!< this is the number of pending
					writes in the given flush type */
	os_event_t	no_flush[BUF_FLUSH_N_TYPES];
					/*!< this is in the set state
					when there is no flush batch
					of the given type running */
	ib_rbt_t*	flush_rbt;	/*!< a red-black tree is used
					exclusively during recovery to
					speed up insertions in the
					flush_list. This tree contains
					blocks in order of
					oldest_modification LSN and is
					kept in sync with the
					flush_list.
					Each member of the tree MUST
					also be on the flush_list.
					This tree is relevant only in
					recovery and is set to NULL
					once the recovery is over.
					Protected by flush_list_mutex */
	ulint		freed_page_clock;/*!< a sequence number used
					to count the number of buffer
					blocks removed from the end of
					the LRU list; NOTE that this
					counter may wrap around at 4
					billion! A thread is allowed
					to read this for heuristic
					purposes without holding any
					mutex or latch */
	ulint		LRU_flush_ended;/*!< when an LRU flush ends for a page,
					this is incremented by one; this is
					set to zero when a buffer block is
					allocated */
	/* @} */

	/** @name LRU replacement algorithm fields */
	/* @{ */

	UT_LIST_BASE_NODE_T(buf_page_t) free;
					/*!< base node of the free
					block list */
	UT_LIST_BASE_NODE_T(buf_page_t) LRU;
					/*!< base node of the LRU list */
	buf_page_t*	LRU_old;	/*!< pointer to the about
					LRU_old_ratio/BUF_LRU_OLD_RATIO_DIV
					oldest blocks in the LRU list;
					NULL if LRU length less than
					BUF_LRU_OLD_MIN_LEN;
					NOTE: when LRU_old != NULL, its length
					should always equal LRU_old_len */
	ulint		LRU_old_len;	/*!< length of the LRU list from
					the block to which LRU_old points
					onward, including that block;
					see buf0lru.c for the restrictions
					on this value; 0 if LRU_old == NULL;
					NOTE: LRU_old_len must be adjusted
					whenever LRU_old shrinks or grows! */

	UT_LIST_BASE_NODE_T(buf_block_t) unzip_LRU;
					/*!< base node of the
					unzip_LRU list */

	/* @} */
	/** @name Buddy allocator fields
	The buddy allocator is used for allocating compressed page
	frames and buf_page_t descriptors of blocks that exist
	in the buffer pool only in compressed form. */
	/* @{ */
#if defined UNIV_DEBUG || defined UNIV_BUF_DEBUG
	UT_LIST_BASE_NODE_T(buf_page_t)	zip_clean;
					/*!< unmodified compressed pages */
#endif /* UNIV_DEBUG || UNIV_BUF_DEBUG */
	UT_LIST_BASE_NODE_T(buf_page_t) zip_free[BUF_BUDDY_SIZES_MAX];
					/*!< buddy free lists */

	buf_page_t			watch[BUF_POOL_WATCH_SIZE];
					/*!< Sentinel records for buffer
					pool watches. Protected by
				       	buf_pool->mutex. */

//#if BUF_BUDDY_HIGH != UNIV_PAGE_SIZE
//# error "BUF_BUDDY_HIGH != UNIV_PAGE_SIZE"
//#endif
#if BUF_BUDDY_LOW > PAGE_ZIP_MIN_SIZE
# error "BUF_BUDDY_LOW > PAGE_ZIP_MIN_SIZE"
#endif
	/* @} */
};

/** @name Accessors for buf_pool->mutex.
Use these instead of accessing buf_pool->mutex directly. */
/* @{ */

/** Test if a buffer pool mutex is owned. */
#define buf_pool_mutex_own(b) mutex_own(&b->mutex)
/** Acquire a buffer pool mutex. */
/* the buf_pool_mutex is changed the latch order */
#define buf_pool_mutex_enter(b) do {		\
	mutex_enter(&b->mutex);		\
} while (0)

/** Test if flush list mutex is owned. */
#define buf_flush_list_mutex_own(b) mutex_own(&b->flush_list_mutex)

/** Acquire the flush list mutex. */
#define buf_flush_list_mutex_enter(b) do {	\
	mutex_enter(&b->flush_list_mutex);	\
} while (0)
/** Release the flush list mutex. */
# define buf_flush_list_mutex_exit(b) do {	\
	mutex_exit(&b->flush_list_mutex);	\
} while (0)



#if defined UNIV_DEBUG || defined UNIV_BUF_DEBUG
/** Forbid the release of the buffer pool mutex. */
# define buf_pool_mutex_exit_forbid(b) do {	\
	ut_ad(buf_pool_mutex_own(b));		\
	b->mutex_exit_forbidden++;		\
} while (0)
/** Allow the release of the buffer pool mutex. */
# define buf_pool_mutex_exit_allow(b) do {	\
	ut_ad(buf_pool_mutex_own(b));		\
	ut_a(b->mutex_exit_forbidden);	\
	b->mutex_exit_forbidden--;		\
} while (0)
/** Release the buffer pool mutex. */
# define buf_pool_mutex_exit(b) do {		\
	ut_a(!b->mutex_exit_forbidden);		\
	mutex_exit(&b->mutex);			\
} while (0)
#else
/** Forbid the release of the buffer pool mutex. */
# define buf_pool_mutex_exit_forbid(b) ((void) 0)
/** Allow the release of the buffer pool mutex. */
# define buf_pool_mutex_exit_allow(b) ((void) 0)
/** Release the buffer pool mutex. */
# define buf_pool_mutex_exit(b) mutex_exit(&b->mutex)
#endif
#endif /* !UNIV_HOTBACKUP */
/* @} */

/**********************************************************************
Let us list the consistency conditions for different control block states.

NOT_USED:	is in free list, not in LRU list, not in flush list, nor
		page hash table
READY_FOR_USE:	is not in free list, LRU list, or flush list, nor page
		hash table
MEMORY:		is not in free list, LRU list, or flush list, nor page
		hash table
FILE_PAGE:	space and offset are defined, is in page hash table
		if io_fix == BUF_IO_WRITE,
			pool: no_flush[flush_type] is in reset state,
			pool: n_flush[flush_type] > 0

		(1) if buf_fix_count == 0, then
			is in LRU list, not in free list
			is in flush list,
				if and only if oldest_modification > 0
			is x-locked,
				if and only if io_fix == BUF_IO_READ
			is s-locked,
				if and only if io_fix == BUF_IO_WRITE

		(2) if buf_fix_count > 0, then
			is not in LRU list, not in free list
			is in flush list,
				if and only if oldest_modification > 0
			if io_fix == BUF_IO_READ,
				is x-locked
			if io_fix == BUF_IO_WRITE,
				is s-locked

State transitions:

NOT_USED => READY_FOR_USE
READY_FOR_USE => MEMORY
READY_FOR_USE => FILE_PAGE
MEMORY => NOT_USED
FILE_PAGE => NOT_USED	NOTE: This transition is allowed if and only if
				(1) buf_fix_count == 0,
				(2) oldest_modification == 0, and
				(3) io_fix == 0.
*/

#ifndef UNIV_NONINL
#include "buf0buf.ic"
#endif

#endif