branches/zip: Note that buf_page_t::list and buf_page_t::in_flush_list

are only protected by buf_pool_mutex, not by the block mutex.

buf_page_release(): Remove the assertion on in_flush_list.
The function is only holding block->mutex, not buf_pool_mutex.
This was reported by Sunny.  This was the only piece of code
that accessed in_flush_list while not holding buf_pool_mutex.

include/buf0buf.h

@@ -1056,9 +1056,10 @@ struct buf_page_struct{
 	/* 2. Page flushing fields; protected by buf_pool_mutex */
 
 	UT_LIST_NODE_T(buf_page_t) list;
-					/* based on state, this is a list
-					node in one of the following lists
-					in buf_pool:
+					/* based on state, this is a
+					list node, protected only by
+					buf_pool_mutex, in one of the
+					following lists in buf_pool:
 
 					BUF_BLOCK_NOT_USED:	free
 					BUF_BLOCK_FILE_PAGE:	flush_list

include/buf0buf.ic

@@ -1056,10 +1056,6 @@ buf_page_release(
 #endif
 	block->page.buf_fix_count--;
 
-	/* Dirty blocks should be in the flush list. */
-	ut_ad(!block->page.oldest_modification
-	      || block->page.in_flush_list);
-
 	mutex_exit(&block->mutex);
 
 	if (rw_latch == RW_S_LATCH) {