branches/zip: Move all fields that are not needed in compression or

decompression from page_zip_des_t to buf_page_t, because the fields
needed in compression are modified without holding the block mutex.
All writes to bit-fields sharing a machine word must be protected
by the same mutex or rw-lock.

buf/buf0buf.c

@@ -616,7 +616,7 @@ buf_block_init(
 	block->n_pointers = 0;
 #endif /* UNIV_DEBUG */
 	page_zip_des_init(&block->page.zip);
-	block->page.zip.state = BUF_BLOCK_NOT_USED;
+	block->page.state = BUF_BLOCK_NOT_USED;
 
 	mutex_create(&block->mutex, SYNC_BUF_BLOCK);
 

fil/fil0fil.c

@@ -2663,8 +2663,7 @@ error_exit2:
 		page_zip_des_t	page_zip;
 		page_zip_set_size(&page_zip, zip_size);
 		page_zip.data = page + UNIV_PAGE_SIZE;
-		page_zip.state = page_zip.n_blobs
-			= page_zip.m_start = page_zip.m_end = 0;
+		page_zip.n_blobs = page_zip.m_start = page_zip.m_end = 0;
 		buf_flush_init_for_writing(page, &page_zip, 0);
 		ret = os_file_write(path, file, page_zip.data, 0, 0, zip_size);
 	}

include/buf0buf.h

@@ -737,11 +737,22 @@ buf_get_free_list_len(void);
 for compressed and uncompressed frames */
 
 struct buf_page_struct{
+	/* None of the following bit-fields must be modified without
+	holding block->mutex, since they can be stored in the same
+	machine word.  Some of them are additionally protected by
+	buf_pool->mutex. */
+
 	ulint		space:32;	/* tablespace id */
 	ulint		offset:32;	/* page number */
-	page_zip_des_t	zip;		/* compressed page; zip.state
-					and zip.flush_type are relevant
-					for all pages */
+
+	ulint		state:3;	/* state of the control block
+					(@see enum buf_page_state); also
+					protected by buf_pool->mutex */
+	ulint		flush_type:2;	/* if this block is currently being
+					flushed to disk, this tells the
+					flush_type (@see enum buf_flush) */
+
+	page_zip_des_t	zip;		/* compressed page */
 	buf_page_t*	hash;		/* node used in chaining to the page
 					hash table */
 

include/buf0buf.ic

@@ -92,7 +92,7 @@ buf_page_get_state(
 					/* out: state */
 	const buf_page_t*	bpage)	/* in: pointer to the control block */
 {
-	enum buf_page_state	state = bpage->zip.state;
+	enum buf_page_state	state = bpage->state;
 
 #ifdef UNIV_DEBUG
 	switch (state) {
@@ -157,7 +157,7 @@ buf_block_set_state(
 		break;
 	}
 #endif /* UNIV_DEBUG */
-	block->page.zip.state = state;
+	block->page.state = state;
 	ut_ad(buf_block_get_state(block) == state);
 }
 
@@ -193,7 +193,7 @@ buf_page_get_flush_type(
 					/* out: flush type */
 	const buf_page_t*	bpage)	/* in: buffer page */
 {
-	enum buf_flush	flush_type = bpage->zip.flush_type;
+	enum buf_flush	flush_type = bpage->flush_type;
 
 #ifdef UNIV_DEBUG
 	switch (flush_type) {
@@ -217,7 +217,7 @@ buf_page_set_flush_type(
 	buf_page_t*	bpage,		/* in: buffer page */
 	enum buf_flush	flush_type)	/* in: flush type */
 {
-	bpage->zip.flush_type = flush_type;
+	bpage->flush_type = flush_type;
 	ut_ad(buf_page_get_flush_type(bpage) == flush_type);
 }
 

include/page0types.h

@@ -31,13 +31,8 @@ page0*.h includes rem0rec.h and may include rem0rec.ic. */
 struct page_zip_des_struct
 {
 	page_zip_t*	data;		/* compressed page data */
-	ulint		state:3;	/* state of the control block
-					(cf. enum buf_page_state) */
-	ulint		flush_type:2;	/* if this block is currently being
-					flushed to disk, this tells the
-					flush_type (cf. enum buf_flush);
-					protected by block->mutex */
-	ulint		:9;		/* reserved */
+
+	ulint		:17;		/* reserved */
 	ulint		n_blobs:12;	/* number of externally stored
 					columns on the page; the maximum
 					is 744 on a 16 KiB page */