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/*****************************************************************************
Copyright (c) 1995, 2011, 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/buf0dblwr.h
Doublewrite buffer module
Created 2011/12/19 Inaam Rana
*******************************************************/
#ifndef buf0dblwr_h
#define buf0dblwr_h
#include "univ.i"
#include "ut0byte.h"
#include "log0log.h"
#ifndef UNIV_HOTBACKUP
/** Doublewrite system */
extern buf_dblwr_t* buf_dblwr;
/** Set to TRUE when the doublewrite buffer is being created */
extern ibool buf_dblwr_being_created;
/****************************************************************//**
Creates the doublewrite buffer to a new InnoDB installation. The header of the
doublewrite buffer is placed on the trx system header page. */
UNIV_INTERN
void
buf_dblwr_create(void);
/*==================*/
/****************************************************************//**
At a database startup initializes the doublewrite buffer memory structure if
we already have a doublewrite buffer created in the data files. If we are
upgrading to an InnoDB version which supports multiple tablespaces, then this
function performs the necessary update operations. If we are in a crash
recovery, this function uses a possible doublewrite buffer to restore
half-written pages in the data files. */
UNIV_INTERN
void
buf_dblwr_init_or_restore_pages(
/*============================*/
ibool restore_corrupt_pages); /*!< in: TRUE=restore pages */
/****************************************************************//**
frees doublewrite buffer. */
UNIV_INTERN
void
buf_dblwr_free(void);
/*================*/
/********************************************************************//**
Updates the doublewrite buffer when an IO request that is part of an
LRU or flush batch is completed. */
UNIV_INTERN
void
buf_dblwr_update(void);
/*==================*/
/****************************************************************//**
Determines if a page number is located inside the doublewrite buffer.
@return TRUE if the location is inside the two blocks of the
doublewrite buffer */
UNIV_INTERN
ibool
buf_dblwr_page_inside(
/*==================*/
ulint page_no); /*!< in: page number */
/********************************************************************//**
Posts a buffer page for writing. If the doublewrite memory buffer is
full, calls buf_dblwr_flush_buffered_writes and waits for for free
space to appear. */
UNIV_INTERN
void
buf_dblwr_add_to_batch(
/*====================*/
buf_page_t* bpage); /*!< in: buffer block to write */
/********************************************************************//**
Flushes possible buffered writes from the doublewrite memory buffer to disk,
and also wakes up the aio thread if simulated aio is used. It is very
important to call this function after a batch of writes has been posted,
and also when we may have to wait for a page latch! Otherwise a deadlock
of threads can occur. */
UNIV_INTERN
void
buf_dblwr_flush_buffered_writes(void);
/*=================================*/
/********************************************************************//**
Writes a page to the doublewrite buffer on disk, sync it, then write
the page to the datafile and sync the datafile. This function is used
for single page flushes. If all the buffers allocated for single page
flushes in the doublewrite buffer are in use we wait here for one to
become free. We are guaranteed that a slot will become free because any
thread that is using a slot must also release the slot before leaving
this function. */
UNIV_INTERN
void
buf_dblwr_write_single_page(
/*========================*/
buf_page_t* bpage); /*!< in: buffer block to write */
/** Doublewrite control struct */
struct buf_dblwr_t{
ib_mutex_t mutex; /*!< mutex protecting the first_free field and
write_buf */
ulint block1; /*!< the page number of the first
doublewrite block (64 pages) */
ulint block2; /*!< page number of the second block */
ulint first_free; /*!< first free position in write_buf measured
in units of UNIV_PAGE_SIZE */
ulint s_reserved; /*!< number of slots currently reserved
for single page flushes. */
ulint b_reserved; /*!< number of slots currently reserved
for batch flush. */
ibool* in_use; /*!< flag used to indicate if a slot is
in use. Only used for single page
flushes. */
ibool batch_running; /*!< set to TRUE if currently a batch
is being written from the doublewrite
buffer. */
byte* write_buf; /*!< write buffer used in writing to the
doublewrite buffer, aligned to an
address divisible by UNIV_PAGE_SIZE
(which is required by Windows aio) */
byte* write_buf_unaligned;
/*!< pointer to write_buf, but unaligned */
buf_page_t**
buf_block_arr; /*!< array to store pointers to the buffer
blocks which have been cached to write_buf */
};
#endif /* UNIV_HOTBACKUP */
#endif
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