branches/zip: Fix and clarify the latching of some buf_block_t members.

buf_block_t::check_index_page_at_flush: Note that this field is not
protected by any mutex. Make it a separate field, not a bitfield that
could share the machine word with other fields.

buf_block_t::lock_hash_val: Note that this field is protected by
buf_block_t::lock (or during block creation, by buf_pool_mutex and
buf_block_t::mutex).

buf_block_get_lock_hash_val(): Assert that block->lock is held by the
current thread.

Issue #465, rb://267 approved by Inaam Rana

ChangeLog

+2010-03-11	The InnoDB Team
+
+	* buf0buf.h, buf0buf.ic:
+	Fix and clarify the latching of some buf_block_t members.
+	Note that check_index_page_at_flush is not protected by any mutex.
+	Note and assert that lock_hash_val is protected by the rw-latch.
+
 2010-03-10	The InnoDB Team
 
 	* trx/trx0sys.c:

include/buf0buf.h

@@ -1179,15 +1179,21 @@ struct buf_block_struct{
 	rw_lock_t	lock;		/*!< read-write lock of the buffer
 					frame */
 	unsigned	lock_hash_val:32;/*!< hashed value of the page address
-					in the record lock hash table */
-	unsigned	check_index_page_at_flush:1;
+					in the record lock hash table;
+					protected by buf_block_t::lock
+					(or buf_block_t::mutex, buf_pool_mutex
+				        in buf_page_get_gen(),
+					buf_page_init_for_read()
+					and buf_page_create()) */
+	ibool		check_index_page_at_flush;
 					/*!< TRUE if we know that this is
 					an index page, and want the database
 					to check its consistency before flush;
 					note that there may be pages in the
 					buffer pool which are index pages,
 					but this flag is not set because
-					we do not keep track of all pages */
+					we do not keep track of all pages;
+					NOT protected by any mutex */
 	/* @} */
 	/** @name Optimistic search field */
 	/* @{ */

include/buf0buf.ic

@@ -705,6 +705,12 @@ buf_block_get_lock_hash_val(
 /*========================*/
 	const buf_block_t*	block)	/*!< in: block */
 {
+	ut_ad(block);
+	ut_ad(buf_page_in_file(&block->page));
+#ifdef UNIV_SYNC_DEBUG
+	ut_ad(rw_lock_own(&(((buf_block_t*) block)->lock), RW_LOCK_EXCLUSIVE)
+	      || rw_lock_own(&(((buf_block_t*) block)->lock), RW_LOCK_SHARED));
+#endif /* UNIV_SYNC_DEBUG */
 	return(block->lock_hash_val);
 }