Merge 10.2 into 10.3

10 files changed, 409 insertions, 43 deletions

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 0813cf2288f..94362c349f2 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -248,12 +248,6 @@ MY_CHECK_AND_SET_COMPILER_FLAG(-ggdb3 DEBUG)
 OPTION(ENABLED_LOCAL_INFILE
  "If we should should enable LOAD DATA LOCAL by default" ${IF_WIN})
 
-OPTION(WITH_INNODB_DISALLOW_WRITES "InnoDB freeze writes patch from Google" ${WITH_WSREP})
-IF (WITH_INNODB_DISALLOW_WRITES)
-  SET(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -DWITH_INNODB_DISALLOW_WRITES")
-  SET(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -DWITH_INNODB_DISALLOW_WRITES")
-ENDIF()
-
 # Set DBUG_OFF and other optional release-only flags for non-debug project types
 FOREACH(BUILD_TYPE RELEASE RELWITHDEBINFO MINSIZEREL)
   FOREACH(LANG C CXX)
@@ -267,7 +261,7 @@ ENDFOREACH()
 
 # Add safemutex for debug configurations, except on Windows
 # (safemutex has never worked on Windows)
-IF(NOT WIN32 AND NOT WITH_INNODB_MEMCACHED)
+IF(NOT WIN32)
   FOREACH(LANG C CXX)
       SET(CMAKE_${LANG}_FLAGS_DEBUG "${CMAKE_${LANG}_FLAGS_DEBUG} -DSAFE_MUTEX")
   ENDFOREACH()
diff --git a/extra/mariabackup/backup_copy.cc b/extra/mariabackup/backup_copy.cc
index 1542e57c84c..a2677f778f4 100644
--- a/extra/mariabackup/backup_copy.cc
+++ b/extra/mariabackup/backup_copy.cc
@@ -1428,6 +1428,10 @@ void backup_release()
 		history_lock_time = time(NULL) - history_lock_time;
 	}
 
+	if (opt_lock_ddl_per_table) {
+		mdl_unlock_all();
+	}
+
 	if (opt_safe_slave_backup && sql_thread_started) {
 		msg("Starting slave SQL thread\n");
 		xb_mysql_query(mysql_connection,
diff --git a/extra/mariabackup/backup_mysql.cc b/extra/mariabackup/backup_mysql.cc
index 0549b0c5e9c..59569fc625d 100644
--- a/extra/mariabackup/backup_mysql.cc
+++ b/extra/mariabackup/backup_mysql.cc
@@ -868,6 +868,76 @@ stop_query_killer()
 	os_event_wait_time(kill_query_thread_stopped, 60000);
 }
 
+
+/*
+Killing connections that wait for MDL lock.
+If lock-ddl-per-table is used, there can be some DDL statements
+
+FLUSH TABLES would hang infinitely, if DDL statements are waiting for
+MDL lock, which mariabackup currently holds. Therefore we start killing
+those  statements from a dedicated thread, until FLUSH TABLES WITH READ LOCK
+succeeds.
+*/
+
+static os_event_t mdl_killer_stop_event;
+static os_event_t mdl_killer_finished_event;
+
+static
+os_thread_ret_t
+DECLARE_THREAD(kill_mdl_waiters_thread(void *))
+{
+	MYSQL	*mysql;
+	if ((mysql = xb_mysql_connect()) == NULL) {
+		msg("Error: kill mdl waiters thread failed to connect\n");
+		goto stop_thread;
+	}
+
+	for(;;){
+		if (os_event_wait_time(mdl_killer_stop_event, 1000) == 0)
+			break;
+
+		MYSQL_RES *result = xb_mysql_query(mysql,
+			"SELECT ID, COMMAND FROM INFORMATION_SCHEMA.PROCESSLIST "
+			" WHERE State='Waiting for table metadata lock'",
+			true, true);
+		while (MYSQL_ROW row = mysql_fetch_row(result))
+		{
+			char query[64];
+			msg_ts("Killing MDL waiting query '%s' on connection '%s'\n",
+				row[1], row[0]);
+			snprintf(query, sizeof(query), "KILL QUERY %s", row[0]);
+			xb_mysql_query(mysql, query, true);
+		}
+	}
+
+	mysql_close(mysql);
+
+stop_thread:
+	msg_ts("Kill mdl waiters thread stopped\n");
+	os_event_set(mdl_killer_finished_event);
+	os_thread_exit();
+	return os_thread_ret_t(0);
+}
+
+
+static void start_mdl_waiters_killer()
+{
+	mdl_killer_stop_event = os_event_create(0);
+	mdl_killer_finished_event = os_event_create(0);
+	os_thread_create(kill_mdl_waiters_thread, 0, 0);
+}
+
+
+/* Tell MDL killer to stop and finish for its completion*/
+static void stop_mdl_waiters_killer()
+{
+	os_event_set(mdl_killer_stop_event);
+	os_event_wait(mdl_killer_finished_event);
+
+	os_event_destroy(mdl_killer_stop_event);
+	os_event_destroy(mdl_killer_finished_event);
+}
+
 /*********************************************************************//**
 Function acquires either a backup tables lock, if supported
 by the server, or a global read lock (FLUSH TABLES WITH READ LOCK)
@@ -890,6 +960,10 @@ lock_tables(MYSQL *connection)
 		return(true);
 	}
 
+	if (opt_lock_ddl_per_table) {
+		start_mdl_waiters_killer();
+	}
+
 	if (!opt_lock_wait_timeout && !opt_kill_long_queries_timeout) {
 
 		/* We do first a FLUSH TABLES. If a long update is running, the
@@ -930,6 +1004,10 @@ lock_tables(MYSQL *connection)
 
 	xb_mysql_query(connection, "FLUSH TABLES WITH READ LOCK", false);
 
+	if (opt_lock_ddl_per_table) {
+		stop_mdl_waiters_killer();
+	}
+
 	if (opt_kill_long_queries_timeout) {
 		stop_query_killer();
 	}
@@ -1647,25 +1725,6 @@ mdl_lock_init()
   }
 }
 
-#ifndef DBUG_OFF
-/* Test  that table is really locked, if lock_ddl_per_table is set.
-   The test is executed in DBUG_EXECUTE_IF block inside mdl_lock_table().
-*/
-static void check_mdl_lock_works(const char *table_name)
-{
-  MYSQL *test_con=  xb_mysql_connect();
-  char *query;
-  xb_a(asprintf(&query,
-		"SET STATEMENT max_statement_time=1 FOR ALTER TABLE %s FORCE",
-		table_name));
-  int err = mysql_query(test_con, query);
-  DBUG_ASSERT(err);
-  int err_no = mysql_errno(test_con);
-  DBUG_ASSERT(err_no == ER_STATEMENT_TIMEOUT);
-  mysql_close(test_con);
-  free(query);
-}
-#endif
 void
 mdl_lock_table(ulint space_id)
 {
@@ -1681,13 +1740,10 @@ mdl_lock_table(ulint space_id)
   while (MYSQL_ROW row = mysql_fetch_row(mysql_result)) {
     std::string full_table_name =  ut_get_name(0,row[0]);
     std::ostringstream lock_query;
-    lock_query << "SELECT * FROM " << full_table_name  << " LIMIT 0";
+    lock_query << "SELECT 1 FROM " << full_table_name  << " LIMIT 0";
 
     msg_ts("Locking MDL for %s\n", full_table_name.c_str());
     xb_mysql_query(mdl_con, lock_query.str().c_str(), false, false);
-
-    DBUG_EXECUTE_IF("check_mdl_lock_works",
-      check_mdl_lock_works(full_table_name.c_str()););
   }
 
   pthread_mutex_unlock(&mdl_lock_con_mutex);
diff --git a/extra/mariabackup/xtrabackup.cc b/extra/mariabackup/xtrabackup.cc
index a75d5ab820f..274bf050886 100644
--- a/extra/mariabackup/xtrabackup.cc
+++ b/extra/mariabackup/xtrabackup.cc
@@ -433,6 +433,91 @@ datafiles_iter_free(datafiles_iter_t *it)
 	free(it);
 }
 
+#ifndef DBUG_OFF
+struct dbug_thread_param_t
+{
+	MYSQL *con;
+	const char *query;
+	int expect_err;
+	int expect_errno;
+	os_event_t done_event;
+};
+
+
+/* Thread procedure used in dbug_start_query_thread. */
+extern "C"
+os_thread_ret_t
+DECLARE_THREAD(dbug_execute_in_new_connection)(void *arg)
+{
+	mysql_thread_init();
+	dbug_thread_param_t *par= (dbug_thread_param_t *)arg;
+	int err = mysql_query(par->con, par->query);
+	int err_no = mysql_errno(par->con);
+	DBUG_ASSERT(par->expect_err == err);
+	if (err && par->expect_errno)
+		DBUG_ASSERT(err_no == par->expect_errno);
+	mysql_close(par->con);
+	mysql_thread_end();
+	os_event_t done = par->done_event;
+	delete par;
+	os_event_set(done);
+	os_thread_exit();
+	return os_thread_ret_t(0);
+}
+
+/*
+Execute query from a new connection, in own thread.
+
+@param query - query to be executed
+@param wait_state - if not NULL, wait until query from new connection
+	reaches this state (value of column State in I_S.PROCESSLIST)
+@param expected_err - if 0, query is supposed to finish successfully,
+	otherwise query should return error.
+@param expected_errno - if not 0, and query finished with error,
+	expected mysql_errno()
+*/
+static os_event_t dbug_start_query_thread(
+	const char *query,
+	const char *wait_state,
+	int expected_err,
+	int expected_errno)
+
+{
+	dbug_thread_param_t *par = new dbug_thread_param_t;
+	par->query = query;
+	par->expect_err = expected_err;
+	par->expect_errno = expected_errno;
+	par->done_event = os_event_create(0);
+	par->con =  xb_mysql_connect();
+	os_thread_create(dbug_execute_in_new_connection, par, 0);
+
+	if (!wait_state)
+		return par->done_event;
+
+	char q[256];
+	snprintf(q, sizeof(q),
+		"SELECT 1 FROM INFORMATION_SCHEMA.PROCESSLIST where ID=%lu"
+		" AND Command='Query' AND State='%s'",
+		mysql_thread_id(par->con), wait_state);
+	for (;;) {
+		MYSQL_RES *result = xb_mysql_query(mysql_connection,q, true, true);
+		if (mysql_fetch_row(result)) {
+			goto end;
+		}
+		msg_ts("Waiting for query '%s' on connection %lu to "
+			" reach state '%s'", query, mysql_thread_id(par->con),
+			wait_state);
+		my_sleep(1000);
+	}
+end:
+	msg_ts("query '%s' on connection %lu reached state '%s'", query,
+	mysql_thread_id(par->con), wait_state);
+	return par->done_event;
+}
+
+os_event_t dbug_alter_thread_done;
+#endif
+
 void mdl_lock_all()
 {
 	mdl_lock_init();
@@ -448,6 +533,11 @@ void mdl_lock_all()
 		mdl_lock_table(node->space->id);
 	}
 	datafiles_iter_free(it);
+
+	DBUG_EXECUTE_IF("check_mdl_lock_works",
+		dbug_alter_thread_done =
+		  dbug_start_query_thread("ALTER TABLE test.t ADD COLUMN mdl_lock_column int",
+			 "Waiting for table metadata lock",1, ER_QUERY_INTERRUPTED););
 }
 
 /** Check if the space id belongs to the table which name should
@@ -2460,7 +2550,6 @@ xtrabackup_copy_logfile(copy_logfile copy)
 
 	recv_sys->parse_start_lsn = log_copy_scanned_lsn;
 	recv_sys->scanned_lsn = log_copy_scanned_lsn;
-	recv_sys->recovered_lsn = log_copy_scanned_lsn;
 
 	start_lsn = ut_uint64_align_down(log_copy_scanned_lsn,
 					 OS_FILE_LOG_BLOCK_SIZE);
@@ -3984,6 +4073,8 @@ reread_log_header:
 
 	/* copy log file by current position */
 	log_copy_scanned_lsn = checkpoint_lsn_start;
+	recv_sys->recovered_lsn = log_copy_scanned_lsn;
+
 	if (xtrabackup_copy_logfile(COPY_FIRST))
 		goto fail;
 
@@ -4070,6 +4161,11 @@ reread_log_header:
 
 		backup_release();
 
+		DBUG_EXECUTE_IF("check_mdl_lock_works",
+			os_event_wait(dbug_alter_thread_done);
+			os_event_destroy(dbug_alter_thread_done);
+		);
+
 		if (ok) {
 			backup_finish();
 		}
@@ -4079,10 +4175,6 @@ reread_log_header:
 		goto fail;
 	}
 
-	if (opt_lock_ddl_per_table) {
-		mdl_unlock_all();
-	}
-
 	xtrabackup_destroy_datasinks();
 
 	msg("mariabackup: Redo log (from LSN " LSN_PF " to " LSN_PF
diff --git a/extra/mariabackup/xtrabackup.h b/extra/mariabackup/xtrabackup.h
index 8eabf8f0e7e..c77485cb4de 100644
--- a/extra/mariabackup/xtrabackup.h
+++ b/extra/mariabackup/xtrabackup.h
@@ -110,6 +110,7 @@ extern my_bool		opt_noversioncheck;
 extern my_bool		opt_no_backup_locks;
 extern my_bool		opt_decompress;
 extern my_bool		opt_remove_original;
+extern my_bool		opt_lock_ddl_per_table;
 
 extern char		*opt_incremental_history_name;
 extern char		*opt_incremental_history_uuid;
diff --git a/mysql-test/main/derived_cond_pushdown.result b/mysql-test/main/derived_cond_pushdown.result
index dd5abde1548..5edd91faf16 100644
--- a/mysql-test/main/derived_cond_pushdown.result
+++ b/mysql-test/main/derived_cond_pushdown.result
@@ -12604,6 +12604,165 @@ EXPLAIN
 DROP TABLE t1,t2;
 SET  sql_mode = DEFAULT;
 #
+# MDEV-15579: incorrect removal of sub-formulas to be pushed
+#             into WHERE of materialized derived with GROUP BY
+#
+CREATE TABLE t1 (a INT, b INT, c INT, d INT);
+CREATE TABLE t2 (x INT, y INT, z INT);
+INSERT INTO t1 VALUES (1,1,66,1), (1,1,56,2), (3,2,42,3);
+INSERT INTO t2 VALUES (1,1,66), (1,12,32);
+SELECT *
+FROM t2,
+(
+SELECT a, b, max(c) AS max_c
+FROM t1
+GROUP BY a
+HAVING max_c > 37
+) AS v1
+WHERE (v1.a=1) AND (v1.b=v1.a) AND
+(v1.a=t2.x) AND (v1.max_c>30);
+x	y	z	a	b	max_c
+1	1	66	1	1	66
+1	12	32	1	1	66
+EXPLAIN SELECT *
+FROM t2,
+(
+SELECT a, b, max(c) AS max_c
+FROM t1
+GROUP BY a
+HAVING max_c > 37
+) AS v1
+WHERE (v1.a=1) AND (v1.b=v1.a) AND
+(v1.a=t2.x) AND (v1.max_c>30);
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t2	ALL	NULL	NULL	NULL	NULL	2	Using where
+1	PRIMARY	<derived2>	ALL	NULL	NULL	NULL	NULL	3	Using where; Using join buffer (flat, BNL join)
+2	DERIVED	t1	ALL	NULL	NULL	NULL	NULL	3	Using where
+EXPLAIN FORMAT=JSON SELECT *
+FROM t2,
+(
+SELECT a, b, max(c) AS max_c
+FROM t1
+GROUP BY a
+HAVING max_c > 37
+) AS v1
+WHERE (v1.a=1) AND (v1.b=v1.a) AND
+(v1.a=t2.x) AND (v1.max_c>30);
+EXPLAIN
+{
+  "query_block": {
+    "select_id": 1,
+    "table": {
+      "table_name": "t2",
+      "access_type": "ALL",
+      "rows": 2,
+      "filtered": 100,
+      "attached_condition": "t2.x = 1"
+    },
+    "block-nl-join": {
+      "table": {
+        "table_name": "<derived2>",
+        "access_type": "ALL",
+        "rows": 3,
+        "filtered": 100,
+        "attached_condition": "v1.a = 1 and v1.b = 1 and v1.max_c > 30"
+      },
+      "buffer_type": "flat",
+      "buffer_size": "256Kb",
+      "join_type": "BNL",
+      "materialized": {
+        "query_block": {
+          "select_id": 2,
+          "having_condition": "max_c > 37 and max_c > 30 and t1.b = 1",
+          "table": {
+            "table_name": "t1",
+            "access_type": "ALL",
+            "rows": 3,
+            "filtered": 100,
+            "attached_condition": "t1.a = 1"
+          }
+        }
+      }
+    }
+  }
+}
+SELECT *
+FROM t2,
+(
+SELECT a, b, d, max(c) AS max_c
+FROM t1
+GROUP BY a,d
+HAVING max_c > 37
+) AS v1
+WHERE (v1.a=1) AND (v1.b=v1.a) AND (v1.b=v1.d) AND
+(v1.a=t2.x) AND (v1.max_c>30);
+x	y	z	a	b	d	max_c
+1	1	66	1	1	1	66
+1	12	32	1	1	1	66
+EXPLAIN SELECT *
+FROM t2,
+(
+SELECT a, b, d, max(c) AS max_c
+FROM t1
+GROUP BY a,d
+HAVING max_c > 37
+) AS v1
+WHERE (v1.a=1) AND (v1.b=v1.a) AND (v1.b=v1.d) AND
+(v1.a=t2.x) AND (v1.max_c>30);
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t2	ALL	NULL	NULL	NULL	NULL	2	Using where
+1	PRIMARY	<derived2>	ALL	NULL	NULL	NULL	NULL	3	Using where; Using join buffer (flat, BNL join)
+2	DERIVED	t1	ALL	NULL	NULL	NULL	NULL	3	Using where
+EXPLAIN FORMAT=JSON SELECT *
+FROM t2,
+(
+SELECT a, b, d, max(c) AS max_c
+FROM t1
+GROUP BY a,d
+HAVING max_c > 37
+) AS v1
+WHERE (v1.a=1) AND (v1.b=v1.a) AND (v1.b=v1.d) AND
+(v1.a=t2.x) AND (v1.max_c>30);
+EXPLAIN
+{
+  "query_block": {
+    "select_id": 1,
+    "table": {
+      "table_name": "t2",
+      "access_type": "ALL",
+      "rows": 2,
+      "filtered": 100,
+      "attached_condition": "t2.x = 1"
+    },
+    "block-nl-join": {
+      "table": {
+        "table_name": "<derived2>",
+        "access_type": "ALL",
+        "rows": 3,
+        "filtered": 100,
+        "attached_condition": "v1.a = 1 and v1.b = 1 and v1.d = 1 and v1.max_c > 30"
+      },
+      "buffer_type": "flat",
+      "buffer_size": "256Kb",
+      "join_type": "BNL",
+      "materialized": {
+        "query_block": {
+          "select_id": 2,
+          "having_condition": "max_c > 37 and max_c > 30 and t1.b = 1",
+          "table": {
+            "table_name": "t1",
+            "access_type": "ALL",
+            "rows": 3,
+            "filtered": 100,
+            "attached_condition": "t1.a = 1 and t1.d = 1"
+          }
+        }
+      }
+    }
+  }
+}
+DROP TABLE t1,t2;
+#
 # MDEV-10855: Pushdown into derived with window functions 
 #
 set @save_optimizer_switch= @@optimizer_switch;
diff --git a/mysql-test/main/derived_cond_pushdown.test b/mysql-test/main/derived_cond_pushdown.test
index e728a9590a1..2188cc00533 100644
--- a/mysql-test/main/derived_cond_pushdown.test
+++ b/mysql-test/main/derived_cond_pushdown.test
@@ -2166,6 +2166,51 @@ DROP TABLE t1,t2;
 SET  sql_mode = DEFAULT;
 
 --echo #
+--echo # MDEV-15579: incorrect removal of sub-formulas to be pushed
+--echo #             into WHERE of materialized derived with GROUP BY
+--echo #
+
+CREATE TABLE t1 (a INT, b INT, c INT, d INT);
+CREATE TABLE t2 (x INT, y INT, z INT);
+
+INSERT INTO t1 VALUES (1,1,66,1), (1,1,56,2), (3,2,42,3);
+INSERT INTO t2 VALUES (1,1,66), (1,12,32);
+
+LET $query=
+SELECT *
+FROM t2,
+(
+  SELECT a, b, max(c) AS max_c
+  FROM t1
+  GROUP BY a
+  HAVING max_c > 37
+) AS v1
+WHERE (v1.a=1) AND (v1.b=v1.a) AND
+      (v1.a=t2.x) AND (v1.max_c>30);
+EVAL $query;
+EVAL EXPLAIN $query;
+EVAL EXPLAIN FORMAT=JSON $query;
+
+LET $query=
+SELECT *
+FROM t2,
+(
+  SELECT a, b, d, max(c) AS max_c
+  FROM t1
+  GROUP BY a,d
+  HAVING max_c > 37
+) AS v1
+WHERE (v1.a=1) AND (v1.b=v1.a) AND (v1.b=v1.d) AND
+      (v1.a=t2.x) AND (v1.max_c>30);
+EVAL $query;
+EVAL EXPLAIN $query;
+EVAL EXPLAIN FORMAT=JSON $query;
+
+DROP TABLE t1,t2;
+
+# Start of 10.3 tests
+
+--echo #
 --echo # MDEV-10855: Pushdown into derived with window functions 
 --echo #
 
diff --git a/sql/table.cc b/sql/table.cc
index 4f90d429ce5..3696241fa1f 100644
--- a/sql/table.cc
+++ b/sql/table.cc
@@ -8451,6 +8451,7 @@ Item* TABLE_LIST::build_pushable_cond_for_table(THD *thd, Item *cond)
       return 0;		
     List_iterator<Item> li(*((Item_cond*) cond)->argument_list());
     Item *item;
+    bool is_fix_needed= false;
     while ((item=li++))
     {
       if (item->get_extraction_flag() == NO_EXTRACTION_FL)
@@ -8464,8 +8465,16 @@ Item* TABLE_LIST::build_pushable_cond_for_table(THD *thd, Item *cond)
 	return 0;
       if (!fix) 
 	continue;
+
+      if (fix->type() == Item::COND_ITEM &&
+          ((Item_cond*) fix)->functype() == Item_func::COND_AND_FUNC)
+	is_fix_needed= true;
+
       new_cond->argument_list()->push_back(fix, thd->mem_root);
     }
+    if (is_fix_needed)
+      new_cond->fix_fields(thd, 0);
+
     switch (new_cond->argument_list()->elements) 
     {
     case 0:
diff --git a/storage/innobase/innodb.cmake b/storage/innobase/innodb.cmake
index 71c9cc8594b..c053924a948 100644
--- a/storage/innobase/innodb.cmake
+++ b/storage/innobase/innodb.cmake
@@ -219,6 +219,12 @@ ELSE()
    ADD_DEFINITIONS(-DMUTEX_SYS)
 ENDIF()
 
+OPTION(WITH_INNODB_DISALLOW_WRITES "InnoDB freeze writes patch from Google" ${WITH_WSREP})
+IF (WITH_INNODB_DISALLOW_WRITES)
+  ADD_DEFINITIONS(-DWITH_INNODB_DISALLOW_WRITES)
+ENDIF()
+
+
 # Include directories under innobase
 INCLUDE_DIRECTORIES(${CMAKE_SOURCE_DIR}/storage/innobase/include
 		    ${CMAKE_SOURCE_DIR}/storage/innobase/handler)
diff --git a/storage/innobase/log/log0log.cc b/storage/innobase/log/log0log.cc
index 7da66c04c18..1047e93153a 100644
--- a/storage/innobase/log/log0log.cc
+++ b/storage/innobase/log/log0log.cc
@@ -1085,17 +1085,17 @@ log_buffer_switch()
 						 OS_FILE_LOG_BLOCK_SIZE);
 
 	if (log_sys->first_in_use) {
+		log_sys->first_in_use = false;
 		ut_ad(log_sys->buf == ut_align(log_sys->buf,
 					       OS_FILE_LOG_BLOCK_SIZE));
 		log_sys->buf += log_sys->buf_size;
 	} else {
+		log_sys->first_in_use = true;
 		log_sys->buf -= log_sys->buf_size;
 		ut_ad(log_sys->buf == ut_align(log_sys->buf,
 					       OS_FILE_LOG_BLOCK_SIZE));
 	}
 
-	log_sys->first_in_use = !log_sys->first_in_use;
-
 	/* Copy the last block to new buf */
 	ut_memcpy(log_sys->buf,
 		  old_buf + area_end - OS_FILE_LOG_BLOCK_SIZE,
@@ -1235,6 +1235,9 @@ loop:
 	log_group_set_fields(&log_sys->log, log_sys->write_lsn);
 
 	log_mutex_exit();
+	/* Erase the end of the last log block. */
+	memset(write_buf + end_offset, 0, ~end_offset & OS_FILE_LOG_BLOCK_SIZE);
+
 	/* Calculate pad_size if needed. */
 	pad_size = 0;
 	if (write_ahead_size > OS_FILE_LOG_BLOCK_SIZE) {
@@ -1251,12 +1254,9 @@ loop:
 			/* The first block in the unit was initialized
 			after the last writing.
 			Needs to be written padded data once. */
-			pad_size = write_ahead_size - end_offset_in_unit;
-
-			if (area_end + pad_size > log_sys->buf_size) {
-				pad_size = log_sys->buf_size - area_end;
-			}
-
+			pad_size = std::min(
+				ulint(write_ahead_size) - end_offset_in_unit,
+				log_sys->buf_size - area_end);
 			::memset(write_buf + area_end, 0, pad_size);
 		}
 	}