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

/**************************************************//**
@file include/buf0dblwr.h
Doublewrite buffer module

Created 2011/12/19 Inaam Rana
*******************************************************/

#ifndef buf0dblwr_h
#define buf0dblwr_h

#include "univ.i"
#include "buf0buf.h"
#include "ut0byte.h"
#include "log0log.h"
#include "buf0types.h"
#include "log0recv.h"

#ifndef UNIV_HOTBACKUP

/** Maximum doublewrite batch size. This cannot be set higher than 127, the
legacy innodb_doublewrite_batch_size maximum value, without decoupling the
legacy buffer sizing in the system tablespace from it. */
enum { MAX_DOUBLEWRITE_BATCH_SIZE = 127 };

/** 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.
@return true if successful, false if not. */
__attribute__((warn_unused_result))
bool
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 loads the pages from double write buffer into memory.
@return DB_SUCCESS or error code */
__attribute__((warn_unused_result))
dberr_t
buf_dblwr_init_or_load_pages(
	os_file_t	file,
	const char*	path);

/** Process and remove the double write buffer pages for all tablespaces. */
void
buf_dblwr_process(void);

/****************************************************************//**
frees doublewrite buffer. */
void
buf_dblwr_free(void);
/*================*/
/********************************************************************//**
Updates the doublewrite buffer when an IO request is completed. */
void
buf_dblwr_update(
/*=============*/
	const buf_page_t*	bpage,	/*!< in: buffer block descriptor */
	buf_flush_t		flush_type);/*!< in: flush type */
/****************************************************************//**
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 */
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. */
void
buf_dblwr_add_to_batch(
/*====================*/
	buf_page_t*	bpage,	/*!< in: buffer block to write */
	buf_flush_t	flush_type);/*!< in: BUF_FLUSH_LRU or BUF_FLUSH_LIST */

/********************************************************************//**
Flush a batch of writes to the datafiles that have already been
written to the dblwr buffer on disk. */
void
buf_dblwr_sync_datafiles();

/********************************************************************//**
Flushes possible buffered writes from the specified partition of 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. */
void
buf_dblwr_flush_buffered_writes(
/*============================*/
	ulint dblwr_partition);	/*!< in: doublewrite partition */
/********************************************************************//**
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. */
void
buf_dblwr_write_single_page(
/*========================*/
	buf_page_t*	bpage,	/*!< in: buffer block to write */
	bool		sync);	/*!< in: true if sync IO requested */

/** Return the doublewrite partition number for a given buffer page and flush
type.
@return the doublewrite partition number */
__attribute__((warn_unused_result))
UNIV_INLINE
ulint
buf_parallel_dblwr_partition(const buf_page_t* bpage, buf_flush_t flush_type);

/** Return the doublewrite partition number for a given buffer pool and flush
type.
@return the doublewrite partition number */
__attribute__((warn_unused_result))
UNIV_INLINE
ulint
buf_parallel_dblwr_partition(const buf_pool_t* buf_pool,
			     buf_flush_t flush_type);

/** Initialize parallel doublewrite subsystem: create its data structure and
the disk file.
@return DB_SUCCESS or error code */
__attribute__((warn_unused_result))
dberr_t
buf_parallel_dblwr_create(void);

/** Delete the parallel doublewrite file, if its path already has been
computed. It is up to the caller to ensure that this called at safe point */
void
buf_parallel_dblwr_delete(void);

/** Close and delete the doublewrite buffer file and free its memory data
structure. */
void
buf_parallel_dblwr_destroy(void);

/** Release any unused parallel doublewrite pages and free their underlying
buffer at the end of crash recovery */
void
buf_parallel_dblwr_finish_recovery(void);

/** A single parallel doublewrite partition data structure */
struct parallel_dblwr_shard_t {
	/** First free position in write_buf measured in units of
	UNIV_PAGE_SIZE */
	ulint		first_free;
	/** Number of pages posted to I/O in this doublewrite batch */
	ulint		batch_size;
	/** Raw heap pointer for write_buf */
	byte*		write_buf_unaligned;
	/** Write buffer used in writing to the doublewrite buffer, aligned
	on UNIV_PAGE_SIZE */
	byte*		write_buf;
	/** Array to store pointers to the buffer blocks which have been cached
	to write_buf */
	buf_page_t**	buf_block_arr;
	/** I/O for a doublewrite batch completion event */
	os_event_t	batch_completed;
};

/** Maximum possible number of doublewrite partitions */
enum { MAX_DBLWR_SHARDS = MAX_BUFFER_POOLS * 2 };

/** Parallel doublewrite buffer data structure */
class parallel_dblwr_t {
public:
	/** Parallel doublewrite buffer file handle */
	os_file_t		file;
	/** Path to the parallel doublewrite buffer */
	char*			path;
	/** Individual parallel doublewrite partitions */
	parallel_dblwr_shard_t	shard[MAX_DBLWR_SHARDS];
	/** Buffer for reading in parallel doublewrite buffer pages
	during crash recovery */
	byte*			recovery_buf_unaligned;

	/** Default constructor for the parallel doublewrite instance */
	parallel_dblwr_t(void)
		:
		file(OS_FILE_CLOSED),
		path(NULL),
		recovery_buf_unaligned(NULL)
	{ }
};

/** The parallel doublewrite buffer */
extern parallel_dblwr_t parallel_dblwr_buf;

/** Doublewrite control struct */
struct buf_dblwr_t{
	ib_mutex_t	mutex;	/*!< mutex protecting write_buf */
	ulint		block1;	/*!< the page number of the first
				doublewrite block (64 pages) */
	ulint		block2;	/*!< page number of the second block */
	ulint		s_reserved;/*!< number of slots currently
				reserved for single page flushes. */
	os_event_t	s_event;/*!< event where threads wait for a
				single page flush slot. */
	bool*		in_use;	/*!< flag used to indicate if a slot is
				in use. Only used for single page
				flushes. */
	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 */

#ifndef UNIV_NONINL
#include "buf0dblwr.ic"
#endif

#endif
