From dccaa03753aeb3819aa266afad6b68533a025a43 Mon Sep 17 00:00:00 2001
From: marko <>
Date: Fri, 24 Nov 2006 08:32:18 +0000
Subject: [PATCH] branches/zip: Introduce buf_page_t, a common structure for
 compressed-only and uncompressed buffer pool pages.

buf_block_t: Replace page_zip, space, and offset with buf_page_t page.
Replace some integers with bit-fields.

enum buf_block_state: Rename to buf_page_state.  Add BUF_BLOCK_ZIP_PAGE.

page_zip_des_t: Add the field "state".  Make the integer fields bit-fields.

page_zip_copy(): Document which fields are copied.
---
 buf/buf0buf.c        | 49 ++++++++++++++--------------
 buf/buf0flu.c        | 24 +++++++-------
 buf/buf0lru.c        | 40 ++++++++++++-----------
 buf/buf0rea.c        |  2 +-
 fil/fil0fil.c        |  3 +-
 include/buf0buf.h    | 76 ++++++++++++++++++++++++--------------------
 include/buf0buf.ic   | 31 ++++++++++--------
 include/buf0types.h  |  1 +
 include/page0types.h | 16 +++++++---
 include/page0zip.h   |  4 ++-
 page/page0zip.c      |  4 ++-
 11 files changed, 140 insertions(+), 110 deletions(-)

diff --git a/buf/buf0buf.c b/buf/buf0buf.c
index 1ab362d7bf1..93930cc77a5 100644
--- a/buf/buf0buf.c
+++ b/buf/buf0buf.c
@@ -603,7 +603,7 @@ buf_block_init(
 	buf_block_t*	block,	/* in: pointer to control block */
 	byte*		frame)	/* in: pointer to buffer frame */
 {
-	block->state = BUF_BLOCK_NOT_USED;
+	block->page.zip.state = BUF_BLOCK_NOT_USED;
 
 	block->frame = frame;
 
@@ -625,7 +625,7 @@ buf_block_init(
 #ifdef UNIV_DEBUG
 	block->n_pointers = 0;
 #endif /* UNIV_DEBUG */
-	page_zip_des_init(&block->page_zip);
+	page_zip_des_init(&block->page.zip);
 
 	mutex_create(&block->mutex, SYNC_BUF_BLOCK);
 
@@ -798,7 +798,7 @@ buf_chunk_free(
 
 	for (block = chunk->blocks; block < block_end; block++) {
 		ut_a(buf_block_get_state(block) == BUF_BLOCK_NOT_USED);
-		ut_a(!block->page_zip.data);
+		ut_a(!block->page.zip.data);
 
 		ut_a(!block->in_LRU_list);
 		/* Remove the block from the free list. */
@@ -1081,8 +1081,8 @@ buf_pool_page_hash_rebuild(void)
 			    == BUF_BLOCK_FILE_PAGE) {
 				HASH_INSERT(buf_block_t, hash, page_hash,
 					    buf_page_address_fold(
-						    block->space,
-						    block->offset),
+						    block->page.space,
+						    block->page.offset),
 					    block);
 			}
 		}
@@ -1397,7 +1397,8 @@ loop:
 	if (guess) {
 		block = guess;
 
-		if ((offset != block->offset) || (space != block->space)
+		if (offset != block->page.offset
+		    || space != block->page.space
 		    || buf_block_get_state(block) != BUF_BLOCK_FILE_PAGE) {
 
 			block = NULL;
@@ -1799,12 +1800,12 @@ buf_page_init_for_backup_restore(
 	block->n_fields		= 1;
 	block->n_bytes		= 0;
 	block->left_side	= TRUE;
-	page_zip_des_init(&block->page_zip);
-	/* We assume that block->page_zip.data has been allocated
+	page_zip_des_init(&block->page);
+	/* We assume that block->page.data has been allocated
 	with zip_size == UNIV_PAGE_SIZE. */
 	ut_ad(zip_size <= UNIV_PAGE_SIZE);
 	ut_ad(ut_is_2pow(zip_size));
-	block->page_zip.size = zip_size;
+	block->page.size = zip_size;
 #ifdef UNIV_DEBUG_FILE_ACCESSES
 	block->file_page_was_freed = FALSE;
 #endif /* UNIV_DEBUG_FILE_ACCESSES */
@@ -2127,16 +2128,16 @@ buf_page_io_complete(
 		ulint	read_space_id;
 		byte*	frame;
 
-		if (block->page_zip.size) {
+		if (block->page.zip.size) {
 			ut_a(buf_block_get_space(block) != 0);
 
-			frame = block->page_zip.data;
+			frame = block->page.zip.data;
 
 			switch (fil_page_get_type(frame)) {
 			case FIL_PAGE_INDEX:
 				if (block->frame) {
 					if (!page_zip_decompress(
-						    &block->page_zip,
+						    &block->page.zip,
 						    block->frame)) {
 						goto corrupt;
 					}
@@ -2150,7 +2151,7 @@ buf_page_io_complete(
 			case FIL_PAGE_TYPE_ZBLOB:
 				/* Copy to uncompressed storage. */
 				memcpy(block->frame, frame,
-				       block->page_zip.size);
+				       block->page.zip.size);
 				break;
 			default:
 				ut_print_timestamp(stderr);
@@ -2183,8 +2184,9 @@ buf_page_io_complete(
 				(ulong) buf_block_get_page_no(block));
 		} else if (!read_space_id && !read_page_no) {
 			/* This is likely an uninitialized page. */
-		} else if ((block->space && block->space != read_space_id)
-			   || block->offset != read_page_no) {
+		} else if ((block->page.space
+			    && block->page.space != read_space_id)
+			   || block->page.offset != read_page_no) {
 			/* We did not compare space_id to read_space_id
 			if block->space == 0, because the field on the
 			page may contain garbage in MySQL < 4.1.1,
@@ -2197,13 +2199,14 @@ buf_page_io_complete(
 				"InnoDB: read in are %lu:%lu,"
 				" should be %lu:%lu!\n",
 				(ulong) read_space_id, (ulong) read_page_no,
-				(ulong) block->space, (ulong) block->offset);
+				(ulong) block->page.space,
+				(ulong) block->page.offset);
 		}
 
 		/* From version 3.23.38 up we store the page checksum
 		to the 4 first bytes of the page end lsn field */
 
-		if (buf_page_is_corrupted(frame, block->page_zip.size)) {
+		if (buf_page_is_corrupted(frame, block->page.zip.size)) {
 corrupt:
 			fprintf(stderr,
 				"InnoDB: Database page corruption on disk"
@@ -2211,15 +2214,15 @@ corrupt:
 				"InnoDB: file read of page %lu.\n"
 				"InnoDB: You may have to recover"
 				" from a backup.\n",
-				(ulong) block->offset);
-			buf_page_print(frame, block->page_zip.size);
+				(ulong) block->page.offset);
+			buf_page_print(frame, block->page.zip.size);
 			fprintf(stderr,
 				"InnoDB: Database page corruption on disk"
 				" or a failed\n"
 				"InnoDB: file read of page %lu.\n"
 				"InnoDB: You may have to recover"
 				" from a backup.\n",
-				(ulong) block->offset);
+				(ulong) block->page.offset);
 			fputs("InnoDB: It is also possible that"
 			      " your operating\n"
 			      "InnoDB: system has corrupted its"
@@ -2255,7 +2258,7 @@ corrupt:
 
 		if (!recv_no_ibuf_operations) {
 			ibuf_merge_or_delete_for_page(
-				block, block->space, block->offset,
+				block, block->page.space, block->page.offset,
 				buf_block_get_zip_size(block), TRUE);
 		}
 	}
@@ -2767,8 +2770,8 @@ buf_all_freed(void)
 		if (UNIV_LIKELY_NULL(block)) {
 			fprintf(stderr,
 				"Page %lu %lu still fixed or dirty\n",
-				(ulong) block->space,
-				(ulong) block->offset);
+				(ulong) block->page.space,
+				(ulong) block->page.offset);
 			ut_error;
 		}
 	}
diff --git a/buf/buf0flu.c b/buf/buf0flu.c
index 8fc010f431d..d70f1de7483 100644
--- a/buf/buf0flu.c
+++ b/buf/buf0flu.c
@@ -263,7 +263,7 @@ buf_flush_buffered_writes(void)
 		block = trx_doublewrite->buf_block_arr[i];
 		ut_a(buf_block_get_state(block) == BUF_BLOCK_FILE_PAGE);
 
-		if (UNIV_LIKELY_NULL(block->page_zip.data)) {
+		if (UNIV_LIKELY_NULL(block->page.zip.data)) {
 			/* No simple validate for compressed pages exists. */
 			continue;
 		}
@@ -328,7 +328,7 @@ corrupted_page:
 	for (len2 = 0; len2 + UNIV_PAGE_SIZE <= len;
 	     len2 += UNIV_PAGE_SIZE, i++) {
 		block = trx_doublewrite->buf_block_arr[i];
-		if (UNIV_LIKELY(!block->page_zip.data)
+		if (UNIV_LIKELY(!block->page.zip.data)
 		    && UNIV_UNLIKELY
 		    (memcmp(write_buf + len2 + (FIL_PAGE_LSN + 4),
 			    write_buf + len2
@@ -361,7 +361,7 @@ corrupted_page:
 	for (len2 = 0; len2 + UNIV_PAGE_SIZE <= len;
 	     len2 += UNIV_PAGE_SIZE, i++) {
 		block = trx_doublewrite->buf_block_arr[i];
-		if (UNIV_LIKELY(!block->page_zip.data)
+		if (UNIV_LIKELY(!block->page.zip.data)
 		    && UNIV_UNLIKELY
 		    (memcmp(write_buf + len2 + (FIL_PAGE_LSN + 4),
 			    write_buf + len2
@@ -389,13 +389,13 @@ flush:
 	for (i = 0; i < trx_doublewrite->first_free; i++) {
 		block = trx_doublewrite->buf_block_arr[i];
 		ut_a(buf_block_get_state(block) == BUF_BLOCK_FILE_PAGE);
-		if (UNIV_UNLIKELY(block->page_zip.size)) {
+		if (UNIV_UNLIKELY(block->page.zip.size)) {
 			fil_io(OS_FILE_WRITE | OS_AIO_SIMULATED_WAKE_LATER,
 			       FALSE, buf_block_get_space(block),
-			       block->page_zip.size,
+			       block->page.zip.size,
 			       buf_block_get_page_no(block), 0,
-			       block->page_zip.size,
-			       (void*)block->page_zip.data,
+			       block->page.zip.size,
+			       (void*)block->page.zip.data,
 			       (void*)block);
 			continue;
 		} else if (UNIV_UNLIKELY
@@ -471,13 +471,13 @@ try_again:
 		goto try_again;
 	}
 
-	zip_size = block->page_zip.size;
+	zip_size = block->page.zip.size;
 
 	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,
-		       block->page_zip.data, zip_size);
+		       block->page.zip.data, zip_size);
 		memset(trx_doublewrite->write_buf
 		       + UNIV_PAGE_SIZE * trx_doublewrite->first_free
 		       + zip_size, 0, UNIV_PAGE_SIZE - zip_size);
@@ -607,9 +607,9 @@ buf_flush_write_block_low(
 				   block->newest_modification);
 	if (!srv_use_doublewrite_buf || !trx_doublewrite) {
 		fil_io(OS_FILE_WRITE | OS_AIO_SIMULATED_WAKE_LATER,
-		       FALSE, buf_block_get_space(block), block->page_zip.size,
-		       buf_block_get_page_no(block), 0, block->page_zip.size
-		       ? block->page_zip.size : UNIV_PAGE_SIZE,
+		       FALSE, buf_block_get_space(block), block->page.zip.size,
+		       buf_block_get_page_no(block), 0, block->page.zip.size
+		       ? block->page.zip.size : UNIV_PAGE_SIZE,
 		       (void*)block->frame, (void*)block);
 	} else {
 		buf_flush_post_to_doublewrite_buf(block);
diff --git a/buf/buf0lru.c b/buf/buf0lru.c
index b308abf90e5..744d6668962 100644
--- a/buf/buf0lru.c
+++ b/buf/buf0lru.c
@@ -444,20 +444,20 @@ loop:
 		ut_a(buf_block_get_state(block) != BUF_BLOCK_FILE_PAGE);
 		ut_a(!block->in_LRU_list);
 
-		if (block->page_zip.size != zip_size) {
-			block->page_zip.size = zip_size;
-			block->page_zip.n_blobs = 0;
-			block->page_zip.m_start = 0;
-			block->page_zip.m_end = 0;
-			if (block->page_zip.data) {
-				ut_free(block->page_zip.data);
+		if (block->page.zip.size != zip_size) {
+			block->page.zip.size = zip_size;
+			block->page.zip.n_blobs = 0;
+			block->page.zip.m_start = 0;
+			block->page.zip.m_end = 0;
+			if (block->page.zip.data) {
+				ut_free(block->page.zip.data);
 			}
 
 			if (zip_size) {
 				/* TODO: allocate zip from an aligned pool */
-				block->page_zip.data = ut_malloc(zip_size);
+				block->page.zip.data = ut_malloc(zip_size);
 			} else {
-				block->page_zip.data = NULL;
+				block->page.zip.data = NULL;
 			}
 		}
 
@@ -878,11 +878,11 @@ buf_LRU_block_free_non_file_page(
 	memset(block->frame + FIL_PAGE_OFFSET, 0xfe, 4);
 	memset(block->frame + FIL_PAGE_ARCH_LOG_NO_OR_SPACE_ID, 0xfe, 4);
 #endif
-	if (block->page_zip.data) {
+	if (block->page.zip.data) {
 		/* TODO: return zip to an aligned pool */
-		ut_free(block->page_zip.data);
-		block->page_zip.data = NULL;
-		block->page_zip.size = 0;
+		ut_free(block->page.zip.data);
+		block->page.zip.data = NULL;
+		block->page.zip.size = 0;
 	}
 
 	UT_LIST_ADD_FIRST(free, buf_pool->free, block);
@@ -920,21 +920,22 @@ buf_LRU_block_remove_hashed_page(
 
 	buf_block_modify_clock_inc(block);
 
-	hashed_block = buf_page_hash_get(block->space, block->offset);
+	hashed_block = buf_page_hash_get(block->page.space,
+					 block->page.offset);
 
 	if (UNIV_UNLIKELY(block != hashed_block)) {
 		fprintf(stderr,
 			"InnoDB: Error: page %lu %lu not found"
 			" in the hash table\n",
-			(ulong) block->space,
-			(ulong) block->offset);
+			(ulong) block->page.space,
+			(ulong) block->page.offset);
 		if (hashed_block) {
 			fprintf(stderr,
 				"InnoDB: In hash table we find block"
 				" %p of %lu %lu which is not %p\n",
 				(const void*) hashed_block,
-				(ulong) hashed_block->space,
-				(ulong) hashed_block->offset,
+				(ulong) hashed_block->page.space,
+				(ulong) hashed_block->page.offset,
 				(void*) block);
 		}
 
@@ -948,7 +949,8 @@ buf_LRU_block_remove_hashed_page(
 	}
 
 	HASH_DELETE(buf_block_t, hash, buf_pool->page_hash,
-		    buf_page_address_fold(block->space, block->offset),
+		    buf_page_address_fold(block->page.space,
+					  block->page.offset),
 		    block);
 	memset(block->frame + FIL_PAGE_OFFSET, 0xff, 4);
 	memset(block->frame + FIL_PAGE_ARCH_LOG_NO_OR_SPACE_ID, 0xff, 4);
diff --git a/buf/buf0rea.c b/buf/buf0rea.c
index 9d75e3bcbf4..f9e8527be51 100644
--- a/buf/buf0rea.c
+++ b/buf/buf0rea.c
@@ -134,7 +134,7 @@ buf_read_page_low(
 	if (zip_size) {
 		*err = fil_io(OS_FILE_READ | wake_later,
 			      sync, space, zip_size, offset, 0, zip_size,
-			      (void*) block->page_zip.data, (void*) block);
+			      (void*) block->page.zip.data, (void*) block);
 	} else {
 		*err = fil_io(OS_FILE_READ | wake_later,
 			      sync, space, 0, offset, 0, UNIV_PAGE_SIZE,
diff --git a/fil/fil0fil.c b/fil/fil0fil.c
index d354230540f..c3ca82bebbc 100644
--- a/fil/fil0fil.c
+++ b/fil/fil0fil.c
@@ -2660,7 +2660,8 @@ error_exit2:
 		page_zip_des_t	page_zip;
 		page_zip.size = zip_size;
 		page_zip.data = page + UNIV_PAGE_SIZE;
-		page_zip.n_blobs = page_zip.m_start = page_zip.m_end = 0;
+		page_zip.state = page_zip.n_blobs
+			= page_zip.m_start = page_zip.m_end = 0;
 		buf_flush_init_for_writing(page, &page_zip, ut_dulint_zero);
 		ret = os_file_write(path, file, page_zip.data, 0, 0, zip_size);
 	}
diff --git a/include/buf0buf.h b/include/buf0buf.h
index 5df038bbe9d..f12a315b584 100644
--- a/include/buf0buf.h
+++ b/include/buf0buf.h
@@ -66,8 +66,12 @@ extern ulint srv_buf_pool_write_requests; /* variable to count write request
 					  issued */
 
 /* States of a control block */
-enum buf_block_state {
-	BUF_BLOCK_NOT_USED = 211,	/* is in the free list */
+enum buf_page_state {
+	BUF_BLOCK_ZIP_PAGE = 1,		/* contains a compressed page only;
+					must be smaller than
+					BUF_BLOCK_NOT_USED;
+					cf. buf_block_state_valid() */
+	BUF_BLOCK_NOT_USED,		/* is in the free list */
 	BUF_BLOCK_READY_FOR_USE,	/* when buf_get_free_block returns
 					a block, it is in this state */
 	BUF_BLOCK_FILE_PAGE,		/* contains a buffered file page */
@@ -536,7 +540,7 @@ buf_block_dbg_add_level(
 /*************************************************************************
 Gets the state of a block. */
 UNIV_INLINE
-enum buf_block_state
+enum buf_page_state
 buf_block_get_state(
 /*================*/
 					/* out: state */
@@ -549,7 +553,7 @@ void
 buf_block_set_state(
 /*================*/
 	buf_block_t*		block,	/* in/out: pointer to control block */
-	enum buf_block_state	state);	/* in: state */
+	enum buf_page_state	state);	/* in: state */
 /*************************************************************************
 Map a block to a file page. */
 UNIV_INLINE
@@ -702,25 +706,30 @@ buf_get_free_list_len(void);
 
 
 
+/* The common buffer control block structure
+for compressed and uncompressed frames */
+
+struct buf_page_struct{
+	ulint		space:32;	/* tablespace id */
+	ulint		offset:32;	/* page number */
+	page_zip_des_t	zip;		/* compressed page; zip.state
+					is relevant for all pages */
+};
+
 /* The buffer control block structure */
 
 struct buf_block_struct{
 
 	/* 1. General fields */
 
-	ulint		state;		/* state of the control block:
-					BUF_BLOCK_NOT_USED, ...; changing
-					this is only allowed when a thread
-					has BOTH the buffer pool mutex AND
-					block->mutex locked */
+	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 */
-	ulint		space;		/* space id of the page */
-	ulint		offset;		/* page number within the space */
-	ulint		lock_hash_val;	/* hashed value of the page address
-					in the record lock hash table */
 	mutex_t		mutex;		/* mutex protecting this block:
 					state (also protected by the buffer
 					pool mutex), io_fix, buf_fix_count,
@@ -731,7 +740,9 @@ struct buf_block_struct{
 					frame */
 	buf_block_t*	hash;		/* node used in chaining to the page
 					hash table */
-	ibool		check_index_page_at_flush;
+	ulint		lock_hash_val:32;/* hashed value of the page address
+					in the record lock hash table */
+	ulint		check_index_page_at_flush:1;
 					/* TRUE if we know that this is
 					an index page, and want the database
 					to check its consistency before flush;
@@ -785,20 +796,20 @@ struct buf_block_struct{
 					without holding any mutex or latch */
 	ibool		old;		/* TRUE if the block is in the old
 					blocks in the LRU list */
-	ibool		accessed;	/* TRUE if the page has been accessed
+	ulint		accessed:1;	/* TRUE if the page has been accessed
 					while in the buffer pool: read-ahead
 					may read in pages which have not been
 					accessed yet; this is protected by
 					block->mutex; a thread is allowed to
 					read this for heuristic purposes
 					without holding any mutex or latch */
-	ulint		buf_fix_count;	/* count of how manyfold this block
-					is currently bufferfixed; this is
-					protected by block->mutex */
-	ulint		io_fix;		/* if a read is pending to the frame,
+	ulint		io_fix:2;	/* if a read is pending to the frame,
 					io_fix is BUF_IO_READ, in the case
 					of a write BUF_IO_WRITE, otherwise 0;
 					this is protected by block->mutex */
+	ulint		buf_fix_count:29;/* count of how manyfold this block
+					is currently bufferfixed; this is
+					protected by block->mutex */
 	/* 4. Optimistic search field */
 
 	dulint		modify_clock;	/* this clock is incremented every
@@ -835,26 +846,23 @@ struct buf_block_struct{
 	An exception to this is when we init or create a page
 	in the buffer pool in buf0buf.c. */
 
-	ibool		is_hashed;	/* TRUE if hash index has already been
-					built on this page; note that it does
-					not guarantee that the index is
-					complete, though: there may have been
-					hash collisions, record deletions,
-					etc. */
 #ifdef UNIV_DEBUG
 	ulint		n_pointers;	/* used in debugging: the number of
 					pointers in the adaptive hash index
 					pointing to this frame */
 #endif /* UNIV_DEBUG */
-	ulint		curr_n_fields;	/* prefix length for hash indexing:
+	ulint		is_hashed:1;	/* TRUE if hash index has already been
+					built on this page; note that it does
+					not guarantee that the index is
+					complete, though: there may have been
+					hash collisions, record deletions,
+					etc. */
+	ulint		curr_n_fields:10;/* prefix length for hash indexing:
 					number of full fields */
-	ulint		curr_n_bytes;	/* number of bytes in hash indexing */
-	ibool		curr_left_side;	/* TRUE or FALSE in hash indexing */
+	ulint		curr_n_bytes:15;/* number of bytes in hash indexing */
+	ibool		curr_left_side:1;/* TRUE or FALSE in hash indexing */
 	dict_index_t*	index;		/* Index for which the adaptive
 					hash index has been created. */
-	/* TODO: how to protect this? */
-	page_zip_des_t	page_zip;	/* compressed page info */
-
 	/* 6. Debug fields */
 #ifdef UNIV_SYNC_DEBUG
 	rw_lock_t	debug_latch;	/* in the debug version, each thread
@@ -959,9 +967,9 @@ struct buf_pool_struct{
 					LRU_old == NULL */
 };
 
-/* Io_fix states of a control block; these must be != 0 */
-#define BUF_IO_READ		561
-#define BUF_IO_WRITE		562
+/* Io_fix states of a control block; these must be 1..3 */
+#define BUF_IO_READ		1
+#define BUF_IO_WRITE		2
 
 /************************************************************************
 Let us list the consistency conditions for different control block states.
diff --git a/include/buf0buf.ic b/include/buf0buf.ic
index 88361129950..cd4dce783a9 100644
--- a/include/buf0buf.ic
+++ b/include/buf0buf.ic
@@ -86,16 +86,17 @@ buf_pool_clock_tic(void)
 /*************************************************************************
 Gets the state of a block. */
 UNIV_INLINE
-enum buf_block_state
+enum buf_page_state
 buf_block_get_state(
 /*================*/
 					/* out: state */
 	const buf_block_t*	block)	/* in: pointer to the control block */
 {
-	enum buf_block_state	state = block->state;
+	enum buf_page_state	state = block->page.zip.state;
 
 #ifdef UNIV_DEBUG
 	switch (state) {
+	case BUF_BLOCK_ZIP_PAGE:
 	case BUF_BLOCK_NOT_USED:
 	case BUF_BLOCK_READY_FOR_USE:
 	case BUF_BLOCK_FILE_PAGE:
@@ -116,12 +117,15 @@ void
 buf_block_set_state(
 /*================*/
 	buf_block_t*		block,	/* in/out: pointer to control block */
-	enum buf_block_state	state)	/* in: state */
+	enum buf_page_state	state)	/* in: state */
 {
 #ifdef UNIV_DEBUG
-	enum buf_block_state	old_state	= buf_block_get_state(block);
+	enum buf_page_state	old_state	= buf_block_get_state(block);
 
 	switch (old_state) {
+	case BUF_BLOCK_ZIP_PAGE:
+		ut_error;
+		break;
 	case BUF_BLOCK_NOT_USED:
 		ut_a(state == BUF_BLOCK_READY_FOR_USE);
 		break;
@@ -142,7 +146,7 @@ buf_block_set_state(
 		break;
 	}
 #endif /* UNIV_DEBUG */
-	block->state = state;
+	block->page.zip.state = state;
 	ut_ad(buf_block_get_state(block) == state);
 }
 /*************************************************************************
@@ -156,8 +160,8 @@ buf_block_set_file_page(
 	ulint			page_no)/* in: page number */
 {
 	buf_block_set_state(block, BUF_BLOCK_FILE_PAGE);
-	block->space = space;
-	block->offset = page_no;
+	block->page.space = space;
+	block->page.offset = page_no;
 }
 
 /*************************************************************************
@@ -189,7 +193,7 @@ buf_block_get_space(
 	ut_ad(block);
 	ut_a(buf_block_get_state(block) == BUF_BLOCK_FILE_PAGE);
 
-	return(block->space);
+	return(block->page.space);
 }
 
 /*************************************************************************
@@ -204,7 +208,7 @@ buf_block_get_page_no(
 	ut_ad(block);
 	ut_a(buf_block_get_state(block) == BUF_BLOCK_FILE_PAGE);
 
-	return(block->offset);
+	return(block->page.offset);
 }
 
 /*************************************************************************
@@ -216,7 +220,7 @@ buf_block_get_zip_size(
 					/* out: compressed page size, or 0 */
 	const buf_block_t*	block)	/* in: pointer to the control block */
 {
-	return(block->page_zip.size);
+	return(block->page.zip.size);
 }
 
 /*************************************************************************
@@ -229,8 +233,8 @@ buf_block_get_page_zip(
 				/* out: compressed page descriptor, or NULL */
 	buf_block_t*	block)	/* in: pointer to the control block */
 {
-	if (UNIV_LIKELY_NULL(block->page_zip.data)) {
-		return(&block->page_zip);
+	if (UNIV_LIKELY_NULL(block->page.zip.data)) {
+		return(&block->page.zip);
 	}
 
 	return(NULL);
@@ -517,7 +521,8 @@ buf_page_hash_get(
 	fold = buf_page_address_fold(space, offset);
 
 	HASH_SEARCH(hash, buf_pool->page_hash, fold, block,
-		    (block->space == space) && (block->offset == offset));
+		    block->page.space == space
+		    && block->page.offset == offset);
 	ut_a(!block || buf_block_get_state(block) == BUF_BLOCK_FILE_PAGE);
 
 	return(block);
diff --git a/include/buf0types.h b/include/buf0types.h
index a35f5702d6a..ca60960730b 100644
--- a/include/buf0types.h
+++ b/include/buf0types.h
@@ -9,6 +9,7 @@ Created 11/17/1995 Heikki Tuuri
 #ifndef buf0types_h
 #define buf0types_h
 
+typedef	struct buf_page_struct		buf_page_t;
 typedef	struct buf_block_struct		buf_block_t;
 typedef struct buf_chunk_struct		buf_chunk_t;
 typedef	struct buf_pool_struct		buf_pool_t;
diff --git a/include/page0types.h b/include/page0types.h
index bb32a63bdf8..84bae40ca4d 100644
--- a/include/page0types.h
+++ b/include/page0types.h
@@ -31,11 +31,17 @@ page0*.h includes rem0rec.h and may include rem0rec.ic. */
 struct page_zip_des_struct
 {
 	page_zip_t*	data;		/* compressed page data */
-	ulint		size;		/* total size of compressed page */
-	ulint		n_blobs;	/* number of externally stored
-					columns */
-	ulint		m_start;	/* start offset of modification log */
-	ulint		m_end;		/* end offset of modification log */
+	ulint		state:3;	/* state of the control block
+					(cf. enum buf_page_state) */
+	ulint		:1;		/* reserved */
+	ulint		n_blobs:12;	/* number of externally stored
+					columns on the page; the maximum
+					is 744 on a 16 KiB page */
+	ulint		size:16;	/* compressed page size in bytes;
+					must be a power of 2 and
+					at least PAGE_ZIP_MIN_SIZE */
+	ulint		m_start:16;	/* start offset of modification log */
+	ulint		m_end:16;	/* end offset of modification log */
 };
 
 #define PAGE_ZIP_MIN_SIZE	1024	/* smallest page_zip_des_struct.size */
diff --git a/include/page0zip.h b/include/page0zip.h
index 43fee15f738..509e027792f 100644
--- a/include/page0zip.h
+++ b/include/page0zip.h
@@ -348,7 +348,9 @@ Copy a page byte for byte, except for the file page header and trailer. */
 void
 page_zip_copy(
 /*==========*/
-	page_zip_des_t*		page_zip,	/* out: copy of src_zip */
+	page_zip_des_t*		page_zip,	/* out: copy of src_zip
+						(n_blobs, m_start, m_end,
+						data[0..size-1]) */
 	page_t*			page,		/* out: copy of src */
 	const page_zip_des_t*	src_zip,	/* in: compressed page */
 	const page_t*		src,		/* in: page */
diff --git a/page/page0zip.c b/page/page0zip.c
index fa670f8c5c2..23b9978a9cd 100644
--- a/page/page0zip.c
+++ b/page/page0zip.c
@@ -3571,7 +3571,9 @@ Copy a page byte for byte, except for the file page header and trailer. */
 void
 page_zip_copy(
 /*==========*/
-	page_zip_des_t*		page_zip,	/* out: copy of src_zip */
+	page_zip_des_t*		page_zip,	/* out: copy of src_zip
+						(n_blobs, m_start, m_end,
+						data[0..size-1]) */
 	page_t*			page,		/* out: copy of src */
 	const page_zip_des_t*	src_zip,	/* in: compressed page */
 	const page_t*		src,		/* in: page */