1 files changed, 35 insertions, 4 deletions

diff --git a/storage/xtradb/mtr/mtr0mtr.c b/storage/xtradb/mtr/mtr0mtr.c
index 092bd702115..9eb7b18f301 100644
--- a/storage/xtradb/mtr/mtr0mtr.c
+++ b/storage/xtradb/mtr/mtr0mtr.c
@@ -38,6 +38,25 @@ Created 11/26/1995 Heikki Tuuri
 
 #ifndef UNIV_HOTBACKUP
 # include "log0recv.h"
+
+/***************************************************//**
+Checks if a mini-transaction is dirtying a clean page.
+@return TRUE if the mtr is dirtying a clean page. */
+UNIV_INTERN
+ibool
+mtr_block_dirtied(
+/*==============*/
+	const buf_block_t*	block)	/*!< in: block being x-fixed */
+{
+	ut_ad(buf_block_get_state(block) == BUF_BLOCK_FILE_PAGE);
+	ut_ad(block->page.buf_fix_count > 0);
+
+	/* It is OK to read oldest_modification because no
+	other thread can be performing a write of it and it
+	is only during write that the value is reset to 0. */
+	return(block->page.oldest_modification == 0);
+}
+
 /*****************************************************************//**
 Releases the item in the slot given. */
 static
@@ -126,7 +145,7 @@ mtr_memo_slot_note_modification(
 		buf_block_t*	block = (buf_block_t*) slot->object;
 
 #ifdef UNIV_DEBUG
-		ut_ad(log_flush_order_mutex_own());
+		ut_ad(!mtr->made_dirty || log_flush_order_mutex_own());
 #endif /* UNIV_DEBUG */
 		buf_flush_note_modification(block, mtr);
 	}
@@ -202,12 +221,14 @@ mtr_log_reserve_and_write(
 			Add pages to flush list and exit */
 			goto func_exit;
 		}
+	} else {
+		mutex_enter(&log_sys->mutex);
 	}
 
 	data_size = dyn_array_get_data_size(mlog);
 
 	/* Open the database log for log_write_low */
-	mtr->start_lsn = log_reserve_and_open(data_size);
+	mtr->start_lsn = log_open(data_size);
 
 	if (mtr->log_mode == MTR_LOG_ALL) {
 
@@ -226,7 +247,15 @@ mtr_log_reserve_and_write(
 	mtr->end_lsn = log_close();
 
 func_exit:
-	log_flush_order_mutex_enter();
+
+	/* No need to acquire log_flush_order_mutex if this mtr has
+	not dirtied a clean page. log_flush_order_mutex is used to
+	ensure ordered insertions in the flush_list. We need to
+	insert in the flush_list iff the page in question was clean
+	before modifications. */
+	if (mtr->made_dirty) {
+		log_flush_order_mutex_enter();
+	}
 
 	/* It is now safe to release the log mutex because the
 	flush_order mutex will ensure that we are the first one
@@ -237,7 +266,9 @@ func_exit:
 		mtr_memo_note_modifications(mtr);
 	}
 
-	log_flush_order_mutex_exit();
+	if (mtr->made_dirty) {
+		log_flush_order_mutex_exit();
+	}
 }
 #endif /* !UNIV_HOTBACKUP */