~drizzle-trunk/drizzle/development

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

The database buffer buf_pool flush algorithm

(c) 1995-2001 Innobase Oy

Created 11/11/1995 Heikki Tuuri

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

#include "buf0flu.h"

#ifdef UNIV_NONINL

#include "buf0flu.ic"

#include "trx0sys.h"

#endif

#include "ut0byte.h"

#include "ut0lst.h"

#include "page0page.h"

#include "page0zip.h"

#include "fil0fil.h"

#include "buf0buf.h"

#include "buf0lru.h"

#include "buf0rea.h"

#include "ibuf0ibuf.h"

#include "log0log.h"

#include "os0file.h"

#include "trx0sys.h"

#include "srv0srv.h"

#if defined UNIV_DEBUG || defined UNIV_BUF_DEBUG

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

Validates the flush list. */

static

ibool

buf_flush_validate_low(void);

/*========================*/

		/* out: TRUE if ok */

#endif /* UNIV_DEBUG || UNIV_BUF_DEBUG */

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

Inserts a modified block into the flush list. */

UNIV_INTERN

void

buf_flush_insert_into_flush_list(

/*=============================*/

	buf_page_t*	bpage)	/* in: block which is modified */

{

	ut_ad(buf_pool_mutex_own());

	ut_ad((UT_LIST_GET_FIRST(buf_pool->flush_list) == NULL)

	      || (UT_LIST_GET_FIRST(buf_pool->flush_list)->oldest_modification

		  <= bpage->oldest_modification));

	switch (buf_page_get_state(bpage)) {

	case BUF_BLOCK_ZIP_PAGE:

		mutex_enter(&buf_pool_zip_mutex);

		buf_page_set_state(bpage, BUF_BLOCK_ZIP_DIRTY);

		mutex_exit(&buf_pool_zip_mutex);

		UT_LIST_REMOVE(list, buf_pool->zip_clean, bpage);

		/* fall through */

	case BUF_BLOCK_ZIP_DIRTY:

	case BUF_BLOCK_FILE_PAGE:

		ut_ad(bpage->in_LRU_list);

		ut_ad(bpage->in_page_hash);

		ut_ad(!bpage->in_zip_hash);

		ut_ad(!bpage->in_flush_list);

		ut_d(bpage->in_flush_list = TRUE);

		UT_LIST_ADD_FIRST(list, buf_pool->flush_list, bpage);

		break;

	case BUF_BLOCK_ZIP_FREE:

	case BUF_BLOCK_NOT_USED:

	case BUF_BLOCK_READY_FOR_USE:

	case BUF_BLOCK_MEMORY:

	case BUF_BLOCK_REMOVE_HASH:

		ut_error;

		return;

	}

#if defined UNIV_DEBUG || defined UNIV_BUF_DEBUG

	ut_a(buf_flush_validate_low());

#endif /* UNIV_DEBUG || UNIV_BUF_DEBUG */

}

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

Inserts a modified block into the flush list in the right sorted position.

This function is used by recovery, because there the modifications do not

necessarily come in the order of lsn's. */

UNIV_INTERN

void

buf_flush_insert_sorted_into_flush_list(

/*====================================*/

	buf_page_t*	bpage)	/* in: block which is modified */

{

	buf_page_t*	prev_b;

	buf_page_t*	b;

	ut_ad(buf_pool_mutex_own());

	switch (buf_page_get_state(bpage)) {

	case BUF_BLOCK_ZIP_PAGE:

		mutex_enter(&buf_pool_zip_mutex);

		buf_page_set_state(bpage, BUF_BLOCK_ZIP_DIRTY);

		mutex_exit(&buf_pool_zip_mutex);

		UT_LIST_REMOVE(list, buf_pool->zip_clean, bpage);

		/* fall through */

	case BUF_BLOCK_ZIP_DIRTY:

	case BUF_BLOCK_FILE_PAGE:

		ut_ad(bpage->in_LRU_list);

		ut_ad(bpage->in_page_hash);

		ut_ad(!bpage->in_zip_hash);

		ut_ad(!bpage->in_flush_list);

		ut_d(bpage->in_flush_list = TRUE);

		break;

	case BUF_BLOCK_ZIP_FREE:

	case BUF_BLOCK_NOT_USED:

	case BUF_BLOCK_READY_FOR_USE:

	case BUF_BLOCK_MEMORY:

	case BUF_BLOCK_REMOVE_HASH:

		ut_error;

		return;

	}

	prev_b = NULL;

	b = UT_LIST_GET_FIRST(buf_pool->flush_list);

	while (b && b->oldest_modification > bpage->oldest_modification) {

		ut_ad(b->in_flush_list);

		prev_b = b;

		b = UT_LIST_GET_NEXT(list, b);

	}

	if (prev_b == NULL) {

		UT_LIST_ADD_FIRST(list, buf_pool->flush_list, bpage);

	} else {

		UT_LIST_INSERT_AFTER(list, buf_pool->flush_list,

				     prev_b, bpage);

	}

#if defined UNIV_DEBUG || defined UNIV_BUF_DEBUG

	ut_a(buf_flush_validate_low());

#endif /* UNIV_DEBUG || UNIV_BUF_DEBUG */

}

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

Returns TRUE if the file page block is immediately suitable for replacement,

i.e., the transition FILE_PAGE => NOT_USED allowed. */

UNIV_INTERN

ibool

buf_flush_ready_for_replace(

/*========================*/

				/* out: TRUE if can replace immediately */

	buf_page_t*	bpage)	/* in: buffer control block, must be

				buf_page_in_file(bpage) and in the LRU list */

{

	ut_ad(buf_pool_mutex_own());

	ut_ad(mutex_own(buf_page_get_mutex(bpage)));

	ut_ad(bpage->in_LRU_list);

	if (UNIV_LIKELY(buf_page_in_file(bpage))) {

		return(bpage->oldest_modification == 0

		       && buf_page_get_io_fix(bpage) == BUF_IO_NONE

		       && bpage->buf_fix_count == 0);

	}

	ut_print_timestamp(stderr);

	fprintf(stderr,

		"  InnoDB: Error: buffer block state %lu"

		" in the LRU list!\n",

		(ulong) buf_page_get_state(bpage));

	ut_print_buf(stderr, bpage, sizeof(buf_page_t));

	putc('\n', stderr);

	return(FALSE);

}

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

Returns TRUE if the block is modified and ready for flushing. */

UNIV_INLINE

ibool

buf_flush_ready_for_flush(

/*======================*/

				/* out: TRUE if can flush immediately */

	buf_page_t*	bpage,	/* in: buffer control block, must be

				buf_page_in_file(bpage) */

	enum buf_flush	flush_type)/* in: BUF_FLUSH_LRU or BUF_FLUSH_LIST */

{

	ut_a(buf_page_in_file(bpage));

	ut_ad(buf_pool_mutex_own());

	ut_ad(mutex_own(buf_page_get_mutex(bpage)));

	if (bpage->oldest_modification != 0

	    && buf_page_get_io_fix(bpage) == BUF_IO_NONE) {

		ut_ad(bpage->in_flush_list);

		if (flush_type != BUF_FLUSH_LRU) {

			return(TRUE);

		} else if (bpage->buf_fix_count == 0) {

			/* If we are flushing the LRU list, to avoid deadlocks

			we require the block not to be bufferfixed, and hence

			not latched. */

			return(TRUE);

		}

	}

	return(FALSE);

}

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

Remove a block from the flush list of modified blocks. */

UNIV_INTERN

void

buf_flush_remove(

/*=============*/

	buf_page_t*	bpage)	/* in: pointer to the block in question */

{

	ut_ad(buf_pool_mutex_own());

	ut_ad(mutex_own(buf_page_get_mutex(bpage)));

	ut_ad(bpage->in_flush_list);

	ut_d(bpage->in_flush_list = FALSE);

	switch (buf_page_get_state(bpage)) {

	case BUF_BLOCK_ZIP_PAGE:

		/* clean compressed pages should not be on the flush list */

	case BUF_BLOCK_ZIP_FREE:

	case BUF_BLOCK_NOT_USED:

	case BUF_BLOCK_READY_FOR_USE:

	case BUF_BLOCK_MEMORY:

	case BUF_BLOCK_REMOVE_HASH:

		ut_error;

		return;

	case BUF_BLOCK_ZIP_DIRTY:

		buf_page_set_state(bpage, BUF_BLOCK_ZIP_PAGE);

		UT_LIST_REMOVE(list, buf_pool->flush_list, bpage);

		buf_LRU_insert_zip_clean(bpage);

		break;

	case BUF_BLOCK_FILE_PAGE:

		UT_LIST_REMOVE(list, buf_pool->flush_list, bpage);

		break;

	}

	bpage->oldest_modification = 0;

	ut_d(UT_LIST_VALIDATE(list, buf_page_t, buf_pool->flush_list));

}

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

Updates the flush system data structures when a write is completed. */

UNIV_INTERN

void

buf_flush_write_complete(

/*=====================*/

	buf_page_t*	bpage)	/* in: pointer to the block in question */

{

	enum buf_flush	flush_type;

	ut_ad(bpage);

	buf_flush_remove(bpage);

	flush_type = buf_page_get_flush_type(bpage);

	buf_pool->n_flush[flush_type]--;

	if (flush_type == BUF_FLUSH_LRU) {

		/* Put the block to the end of the LRU list to wait to be

		moved to the free list */

		buf_LRU_make_block_old(bpage);

		buf_pool->LRU_flush_ended++;

	}

	/* fprintf(stderr, "n pending flush %lu\n",

	buf_pool->n_flush[flush_type]); */

	if ((buf_pool->n_flush[flush_type] == 0)

	    && (buf_pool->init_flush[flush_type] == FALSE)) {

		/* The running flush batch has ended */

		os_event_set(buf_pool->no_flush[flush_type]);

	}

}

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

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. */

static

void

buf_flush_buffered_writes(void)

/*===========================*/

{

	byte*		write_buf;

	ulint		len;

	ulint		len2;

	ulint		i;

	if (!srv_use_doublewrite_buf || trx_doublewrite == NULL) {

		os_aio_simulated_wake_handler_threads();

		return;

	}

	mutex_enter(&(trx_doublewrite->mutex));

	/* Write first to doublewrite buffer blocks. We use synchronous

	aio and thus know that file write has been completed when the

	control returns. */

	if (trx_doublewrite->first_free == 0) {

		mutex_exit(&(trx_doublewrite->mutex));

		return;

	}

	for (i = 0; i < trx_doublewrite->first_free; i++) {

		const buf_block_t*	block;

		block = (buf_block_t*) trx_doublewrite->buf_block_arr[i];

		if (buf_block_get_state(block) != BUF_BLOCK_FILE_PAGE

		    || block->page.zip.data) {

			/* No simple validate for compressed pages exists. */

			continue;

		}

		if (UNIV_UNLIKELY

		    (memcmp(block->frame + (FIL_PAGE_LSN + 4),

			    block->frame + (UNIV_PAGE_SIZE

					    - FIL_PAGE_END_LSN_OLD_CHKSUM + 4),

			    4))) {

			ut_print_timestamp(stderr);

			fprintf(stderr,

				"  InnoDB: ERROR: The page to be written"

				" seems corrupt!\n"

				"InnoDB: The lsn fields do not match!"

				" Noticed in the buffer pool\n"

				"InnoDB: before posting to the"

				" doublewrite buffer.\n");

		}

		if (!block->check_index_page_at_flush) {

		} else if (page_is_comp(block->frame)) {

			if (UNIV_UNLIKELY

			    (!page_simple_validate_new(block->frame))) {

corrupted_page:

				buf_page_print(block->frame, 0);

				ut_print_timestamp(stderr);

				fprintf(stderr,

					"  InnoDB: Apparent corruption of an"

					" index page n:o %lu in space %lu\n"

					"InnoDB: to be written to data file."

					" We intentionally crash server\n"

					"InnoDB: to prevent corrupt data"

					" from ending up in data\n"

					"InnoDB: files.\n",

					(ulong) buf_block_get_page_no(block),

					(ulong) buf_block_get_space(block));

				ut_error;

			}

		} else if (UNIV_UNLIKELY

			   (!page_simple_validate_old(block->frame))) {

			goto corrupted_page;

		}

	}

	/* increment the doublewrite flushed pages counter */

	srv_dblwr_pages_written+= trx_doublewrite->first_free;

	srv_dblwr_writes++;

	len = ut_min(TRX_SYS_DOUBLEWRITE_BLOCK_SIZE,

		     trx_doublewrite->first_free) * UNIV_PAGE_SIZE;

	write_buf = trx_doublewrite->write_buf;

	i = 0;

	fil_io(OS_FILE_WRITE, TRUE, TRX_SYS_SPACE, 0,

	       trx_doublewrite->block1, 0, len,

	       (void*) write_buf, NULL);

	for (len2 = 0; len2 + UNIV_PAGE_SIZE <= len;

	     len2 += UNIV_PAGE_SIZE, i++) {

		const buf_block_t* block = (buf_block_t*)

			trx_doublewrite->buf_block_arr[i];

		if (UNIV_LIKELY(!block->page.zip.data)

		    && UNIV_LIKELY(buf_block_get_state(block)

				   == BUF_BLOCK_FILE_PAGE)

		    && UNIV_UNLIKELY

		    (memcmp(write_buf + len2 + (FIL_PAGE_LSN + 4),

			    write_buf + len2

			    + (UNIV_PAGE_SIZE

			       - FIL_PAGE_END_LSN_OLD_CHKSUM + 4), 4))) {

			ut_print_timestamp(stderr);

			fprintf(stderr,

				"  InnoDB: ERROR: The page to be written"

				" seems corrupt!\n"

				"InnoDB: The lsn fields do not match!"

				" Noticed in the doublewrite block1.\n");

		}

	}

	if (trx_doublewrite->first_free <= TRX_SYS_DOUBLEWRITE_BLOCK_SIZE) {

		goto flush;

	}

	len = (trx_doublewrite->first_free - TRX_SYS_DOUBLEWRITE_BLOCK_SIZE)

		* UNIV_PAGE_SIZE;

	write_buf = trx_doublewrite->write_buf

		+ TRX_SYS_DOUBLEWRITE_BLOCK_SIZE * UNIV_PAGE_SIZE;

	ut_ad(i == TRX_SYS_DOUBLEWRITE_BLOCK_SIZE);

	fil_io(OS_FILE_WRITE, TRUE, TRX_SYS_SPACE, 0,

	       trx_doublewrite->block2, 0, len,

	       (void*) write_buf, NULL);

	for (len2 = 0; len2 + UNIV_PAGE_SIZE <= len;

	     len2 += UNIV_PAGE_SIZE, i++) {

		const buf_block_t* block = (buf_block_t*)

			trx_doublewrite->buf_block_arr[i];

		if (UNIV_LIKELY(!block->page.zip.data)

		    && UNIV_LIKELY(buf_block_get_state(block)

				   == BUF_BLOCK_FILE_PAGE)

		    && UNIV_UNLIKELY

		    (memcmp(write_buf + len2 + (FIL_PAGE_LSN + 4),

			    write_buf + len2

			    + (UNIV_PAGE_SIZE

			       - FIL_PAGE_END_LSN_OLD_CHKSUM + 4), 4))) {

			ut_print_timestamp(stderr);

			fprintf(stderr,

				"  InnoDB: ERROR: The page to be"

				" written seems corrupt!\n"

				"InnoDB: The lsn fields do not match!"

				" Noticed in"

				" the doublewrite block2.\n");

		}

	}

flush:

	/* Now flush the doublewrite buffer data to disk */

	fil_flush(TRX_SYS_SPACE);

	/* We know that the writes have been flushed to disk now

	and in recovery we will find them in the doublewrite buffer

	blocks. Next do the writes to the intended positions. */

	for (i = 0; i < trx_doublewrite->first_free; i++) {

		const buf_block_t* block = (buf_block_t*)

			trx_doublewrite->buf_block_arr[i];

		ut_a(buf_page_in_file(&block->page));

		if (UNIV_LIKELY_NULL(block->page.zip.data)) {

			fil_io(OS_FILE_WRITE | OS_AIO_SIMULATED_WAKE_LATER,

			       FALSE, buf_page_get_space(&block->page),

			       buf_page_get_zip_size(&block->page),

			       buf_page_get_page_no(&block->page), 0,

			       buf_page_get_zip_size(&block->page),

			       (void*)block->page.zip.data,

			       (void*)block);

			/* Increment the counter of I/O operations used

			for selecting LRU policy. */

			buf_LRU_stat_inc_io();

			continue;

		}

		ut_a(buf_block_get_state(block) == BUF_BLOCK_FILE_PAGE);

		if (UNIV_UNLIKELY(memcmp(block->frame + (FIL_PAGE_LSN + 4),

					 block->frame

					 + (UNIV_PAGE_SIZE

					    - FIL_PAGE_END_LSN_OLD_CHKSUM + 4),

					 4))) {

			ut_print_timestamp(stderr);

			fprintf(stderr,

				"  InnoDB: ERROR: The page to be written"

				" seems corrupt!\n"

				"InnoDB: The lsn fields do not match!"

				" Noticed in the buffer pool\n"

				"InnoDB: after posting and flushing"

				" the doublewrite buffer.\n"

				"InnoDB: Page buf fix count %lu,"

				" io fix %lu, state %lu\n",

				(ulong)block->page.buf_fix_count,

				(ulong)buf_block_get_io_fix(block),

				(ulong)buf_block_get_state(block));

		}

		fil_io(OS_FILE_WRITE | OS_AIO_SIMULATED_WAKE_LATER,

		       FALSE, buf_block_get_space(block), 0,

		       buf_block_get_page_no(block), 0, UNIV_PAGE_SIZE,

		       (void*)block->frame, (void*)block);

		/* Increment the counter of I/O operations used

		for selecting LRU policy. */

		buf_LRU_stat_inc_io();

	}

	/* Wake possible simulated aio thread to actually post the

	writes to the operating system */

	os_aio_simulated_wake_handler_threads();

	/* Wait that all async writes to tablespaces have been posted to

	the OS */

	os_aio_wait_until_no_pending_writes();

	/* Now we flush the data to disk (for example, with fsync) */

	fil_flush_file_spaces(FIL_TABLESPACE);

	/* We can now reuse the doublewrite memory buffer: */

	trx_doublewrite->first_free = 0;

	mutex_exit(&(trx_doublewrite->mutex));

}

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

Posts a buffer page for writing. If the doublewrite memory buffer is

full, calls buf_flush_buffered_writes and waits for for free space to

appear. */

static

void

buf_flush_post_to_doublewrite_buf(

/*==============================*/

	buf_page_t*	bpage)	/* in: buffer block to write */

{

	ulint	zip_size;

try_again:

	mutex_enter(&(trx_doublewrite->mutex));

	ut_a(buf_page_in_file(bpage));

	if (trx_doublewrite->first_free

	    >= 2 * TRX_SYS_DOUBLEWRITE_BLOCK_SIZE) {

		mutex_exit(&(trx_doublewrite->mutex));

		buf_flush_buffered_writes();

		goto try_again;

	}

	zip_size = buf_page_get_zip_size(bpage);

	if (UNIV_UNLIKELY(zip_size)) {

		/* Copy the compressed page and clear the rest. */

		memcpy(trx_doublewrite->write_buf

		       + UNIV_PAGE_SIZE * trx_doublewrite->first_free,

		       bpage->zip.data, zip_size);

		memset(trx_doublewrite->write_buf

		       + UNIV_PAGE_SIZE * trx_doublewrite->first_free

		       + zip_size, 0, UNIV_PAGE_SIZE - zip_size);

	} else {

		ut_a(buf_page_get_state(bpage) == BUF_BLOCK_FILE_PAGE);

		memcpy(trx_doublewrite->write_buf

		       + UNIV_PAGE_SIZE * trx_doublewrite->first_free,

		       ((buf_block_t*) bpage)->frame, UNIV_PAGE_SIZE);

	}

	trx_doublewrite->buf_block_arr[trx_doublewrite->first_free] = bpage;

	trx_doublewrite->first_free++;

	if (trx_doublewrite->first_free

	    >= 2 * TRX_SYS_DOUBLEWRITE_BLOCK_SIZE) {

		mutex_exit(&(trx_doublewrite->mutex));

		buf_flush_buffered_writes();

		return;

	}

	mutex_exit(&(trx_doublewrite->mutex));

}

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

Initializes a page for writing to the tablespace. */

UNIV_INTERN

void

buf_flush_init_for_writing(

/*=======================*/

	byte*		page,		/* in/out: page */

	void*		page_zip_,	/* in/out: compressed page, or NULL */

	ib_uint64_t	newest_lsn)	/* in: newest modification lsn

					to the page */

{

	ut_ad(page);

	if (page_zip_) {

		page_zip_des_t*	page_zip = page_zip_;

		ulint		zip_size = page_zip_get_size(page_zip);

		ut_ad(zip_size);

		ut_ad(ut_is_2pow(zip_size));

		ut_ad(zip_size <= UNIV_PAGE_SIZE);

		switch (UNIV_EXPECT(fil_page_get_type(page), FIL_PAGE_INDEX)) {

		case FIL_PAGE_TYPE_ALLOCATED:

		case FIL_PAGE_INODE:

		case FIL_PAGE_IBUF_BITMAP:

		case FIL_PAGE_TYPE_FSP_HDR:

		case FIL_PAGE_TYPE_XDES:

			/* These are essentially uncompressed pages. */

			memcpy(page_zip->data, page, zip_size);

			/* fall through */

		case FIL_PAGE_TYPE_ZBLOB:

		case FIL_PAGE_TYPE_ZBLOB2:

		case FIL_PAGE_INDEX:

			mach_write_ull(page_zip->data

				       + FIL_PAGE_LSN, newest_lsn);

			memset(page_zip->data + FIL_PAGE_FILE_FLUSH_LSN, 0, 8);

			mach_write_to_4(page_zip->data

					+ FIL_PAGE_SPACE_OR_CHKSUM,

					srv_use_checksums

					? page_zip_calc_checksum(

						page_zip->data, zip_size)

					: BUF_NO_CHECKSUM_MAGIC);

			return;

		}

		ut_print_timestamp(stderr);

		fputs("  InnoDB: ERROR: The compressed page to be written"

		      " seems corrupt:", stderr);

		ut_print_buf(stderr, page, zip_size);

		fputs("\nInnoDB: Possibly older version of the page:", stderr);

		ut_print_buf(stderr, page_zip->data, zip_size);

		putc('\n', stderr);

		ut_error;

	}

	/* Write the newest modification lsn to the page header and trailer */

	mach_write_ull(page + FIL_PAGE_LSN, newest_lsn);

	mach_write_ull(page + UNIV_PAGE_SIZE - FIL_PAGE_END_LSN_OLD_CHKSUM,

		       newest_lsn);

	/* Store the new formula checksum */

	mach_write_to_4(page + FIL_PAGE_SPACE_OR_CHKSUM,

			srv_use_checksums

			? buf_calc_page_new_checksum(page)

			: BUF_NO_CHECKSUM_MAGIC);

	/* We overwrite the first 4 bytes of the end lsn field to store

	the old formula checksum. Since it depends also on the field

	FIL_PAGE_SPACE_OR_CHKSUM, it has to be calculated after storing the

	new formula checksum. */

	mach_write_to_4(page + UNIV_PAGE_SIZE - FIL_PAGE_END_LSN_OLD_CHKSUM,

			srv_use_checksums

			? buf_calc_page_old_checksum(page)

			: BUF_NO_CHECKSUM_MAGIC);

}

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

Does an asynchronous write of a buffer page. NOTE: in simulated aio and

also when the doublewrite buffer is used, we must call

buf_flush_buffered_writes after we have posted a batch of writes! */

static

void

buf_flush_write_block_low(

/*======================*/

	buf_page_t*	bpage)	/* in: buffer block to write */

{

	ulint	zip_size	= buf_page_get_zip_size(bpage);

	page_t*	frame		= NULL;

#ifdef UNIV_LOG_DEBUG

	static ibool univ_log_debug_warned;

#endif /* UNIV_LOG_DEBUG */

	ut_ad(buf_page_in_file(bpage));

#ifdef UNIV_IBUF_COUNT_DEBUG

	ut_a(ibuf_count_get(bpage->space, bpage->offset) == 0);

#endif

	ut_ad(bpage->newest_modification != 0);

#ifdef UNIV_LOG_DEBUG

	if (!univ_log_debug_warned) {

		univ_log_debug_warned = TRUE;

		fputs("Warning: cannot force log to disk if"

		      " UNIV_LOG_DEBUG is defined!\n"

		      "Crash recovery will not work!\n",

		      stderr);

	}

#else

	/* Force the log to the disk before writing the modified block */

	log_write_up_to(bpage->newest_modification, LOG_WAIT_ALL_GROUPS, TRUE);

#endif

	switch (buf_page_get_state(bpage)) {

	case BUF_BLOCK_ZIP_FREE:

	case BUF_BLOCK_ZIP_PAGE: /* The page should be dirty. */

	case BUF_BLOCK_NOT_USED:

	case BUF_BLOCK_READY_FOR_USE:

	case BUF_BLOCK_MEMORY:

	case BUF_BLOCK_REMOVE_HASH:

		ut_error;

		break;

	case BUF_BLOCK_ZIP_DIRTY:

		frame = bpage->zip.data;

		if (UNIV_LIKELY(srv_use_checksums)) {

			ut_a(mach_read_from_4(frame + FIL_PAGE_SPACE_OR_CHKSUM)

			     == page_zip_calc_checksum(frame, zip_size));

		}

		mach_write_ull(frame + FIL_PAGE_LSN,

			       bpage->newest_modification);

		memset(frame + FIL_PAGE_FILE_FLUSH_LSN, 0, 8);

		break;

	case BUF_BLOCK_FILE_PAGE:

		frame = bpage->zip.data;

		if (!frame) {

			frame = ((buf_block_t*) bpage)->frame;

		}

		buf_flush_init_for_writing(((buf_block_t*) bpage)->frame,

					   bpage->zip.data

					   ? &bpage->zip : NULL,

					   bpage->newest_modification);

		break;

	}

	if (!srv_use_doublewrite_buf || !trx_doublewrite) {

		fil_io(OS_FILE_WRITE | OS_AIO_SIMULATED_WAKE_LATER,

		       FALSE, buf_page_get_space(bpage), zip_size,

		       buf_page_get_page_no(bpage), 0,

		       zip_size ? zip_size : UNIV_PAGE_SIZE,

		       frame, bpage);

	} else {

		buf_flush_post_to_doublewrite_buf(bpage);

	}

}

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

Writes a page asynchronously from the buffer buf_pool to a file, if it can be

found in the buf_pool and it is in a flushable state. NOTE: in simulated aio

we must call os_aio_simulated_wake_handler_threads after we have posted a batch

of writes! */

static

ulint

buf_flush_try_page(

/*===============*/

					/* out: 1 if a page was

					flushed, 0 otherwise */

	ulint		space,		/* in: space id */

	ulint		offset,		/* in: page offset */

	enum buf_flush	flush_type)	/* in: BUF_FLUSH_LRU, BUF_FLUSH_LIST,

					or BUF_FLUSH_SINGLE_PAGE */

{

	buf_page_t*	bpage;

	mutex_t*	block_mutex;

	ibool		locked;

	ut_ad(flush_type == BUF_FLUSH_LRU || flush_type == BUF_FLUSH_LIST

	      || flush_type == BUF_FLUSH_SINGLE_PAGE);

	buf_pool_mutex_enter();

	bpage = buf_page_hash_get(space, offset);

	if (!bpage) {

		buf_pool_mutex_exit();

		return(0);

	}

	ut_a(buf_page_in_file(bpage));

	block_mutex = buf_page_get_mutex(bpage);

	mutex_enter(block_mutex);

	if (!buf_flush_ready_for_flush(bpage, flush_type)) {

		mutex_exit(block_mutex);

		buf_pool_mutex_exit();

		return(0);

	}

	switch (flush_type) {

	case BUF_FLUSH_LIST:

		buf_page_set_io_fix(bpage, BUF_IO_WRITE);

		buf_page_set_flush_type(bpage, flush_type);

		if (buf_pool->n_flush[flush_type] == 0) {

			os_event_reset(buf_pool->no_flush[flush_type]);

		}

		buf_pool->n_flush[flush_type]++;

		/* If the simulated aio thread is not running, we must

		not wait for any latch, as we may end up in a deadlock:

		if buf_fix_count == 0, then we know we need not wait */

		locked = bpage->buf_fix_count == 0;

		if (locked

		    && buf_page_get_state(bpage) == BUF_BLOCK_FILE_PAGE) {

			rw_lock_s_lock_gen(&((buf_block_t*) bpage)->lock,

					   BUF_IO_WRITE);

		}

		mutex_exit(block_mutex);

		buf_pool_mutex_exit();

		if (!locked) {

			buf_flush_buffered_writes();

			if (buf_page_get_state(bpage) == BUF_BLOCK_FILE_PAGE) {

				rw_lock_s_lock_gen(&((buf_block_t*) bpage)

						   ->lock, BUF_IO_WRITE);

			}

		}

		break;

	case BUF_FLUSH_LRU:

		/* VERY IMPORTANT:

		Because any thread may call the LRU flush, even when owning

		locks on pages, to avoid deadlocks, we must make sure that the

		s-lock is acquired on the page without waiting: this is

		accomplished because in the if-condition above we require

		the page not to be bufferfixed (in function

		..._ready_for_flush). */

		buf_page_set_io_fix(bpage, BUF_IO_WRITE);

		buf_page_set_flush_type(bpage, flush_type);

		if (buf_pool->n_flush[flush_type] == 0) {

			os_event_reset(buf_pool->no_flush[flush_type]);

		}

		buf_pool->n_flush[flush_type]++;

		if (buf_page_get_state(bpage) == BUF_BLOCK_FILE_PAGE) {

			rw_lock_s_lock_gen(&((buf_block_t*) bpage)->lock,