MDEV-11705: InnoDB: Failing assertion: (&log_sys->mutex)->is_owned() if server...

MDEV-11705: InnoDB: Failing assertion: (&log_sys->mutex)->is_owned() if server started with innodb-scrub-log

Problem was that log_scrub function did not take required log_sys mutex.

Background: Unused space in log blocks are padded with MLOG_DUMMY_RECORD if innodb-scrub-log
is enabled. As log files are written on circular fashion old log blocks can be reused
later for new redo-log entries. Scrubbing pads unused space in log blocks to avoid visibility
of the possible old redo-log contents.

log_scrub(): Take log_sys mutex

log_pad_current_log_block(): Increase srv_stats.n_log_scrubs if padding is done.

srv0srv.cc: Set srv_stats.n_log_scrubs to export vars innodb_scrub_log

ha_innodb.cc: Export innodb_scrub_log to global status.

mysql-test/suite/encryption/r/innodb-scrub-log.result

+create table t1(a int not null primary key auto_increment,
+b varchar(200), c char(100), d varchar(150)) engine=innodb;
+DROP TABLE t1;

mysql-test/suite/encryption/t/innodb-scrub-log.opt

+--loose-innodb-scrub-log=on

mysql-test/suite/encryption/t/innodb-scrub-log.test

+--source include/have_innodb.inc
+
+#
+# MDEV-11705: InnoDB: Failing assertion: (&log_sys->mutex)->is_owned() if server started with innodb-scrub-log
+#
+
+create table t1(a int not null primary key auto_increment,
+b varchar(200), c char(100), d varchar(150)) engine=innodb;
+
+let $wait_condition= SELECT variable_value FROM information_schema.global_status WHERE variable_name = 'innodb_scrub_log';
+--source include/wait_condition.inc
+
+DROP TABLE t1;

storage/innobase/handler/ha_innodb.cc

@@ -1273,6 +1273,9 @@ static SHOW_VAR innodb_status_variables[]= {
   {"scrub_background_page_split_failures_unknown",
    (char*) &export_vars.innodb_scrub_page_split_failures_unknown,
    SHOW_LONG},
+  {"scrub_log",
+   (char*) &export_vars.innodb_scrub_log,
+   SHOW_LONGLONG},
   {"encryption_num_key_requests",
    (char*) &export_vars.innodb_encryption_key_requests, SHOW_LONGLONG},
 

storage/innobase/include/srv0srv.h

@@ -3,7 +3,7 @@
 Copyright (c) 1995, 2016, Oracle and/or its affiliates. All rights reserved.
 Copyright (c) 2008, 2009, Google Inc.
 Copyright (c) 2009, Percona Inc.
-Copyright (c) 2013, 2016, MariaDB Corporation
+Copyright (c) 2013, 2017, MariaDB Corporation
 
 Portions of this file contain modifications contributed and copyrighted by
 Google, Inc. Those modifications are gratefully acknowledged and are described
@@ -194,6 +194,9 @@ struct srv_stats_t {
 
 	/** Number of encryption_get_latest_key_version calls */
 	ulint_ctr_64_t		n_key_requests;
+
+	/** Number of log scrub operations */
+	ulint_ctr_64_t		n_log_scrubs;
 };
 
 extern const char*	srv_main_thread_op_info;
@@ -1118,6 +1121,7 @@ struct export_var_t{
 	ulint innodb_scrub_page_split_failures_out_of_filespace;
 	ulint innodb_scrub_page_split_failures_missing_index;
 	ulint innodb_scrub_page_split_failures_unknown;
+	int64_t innodb_scrub_log;
 };
 
 /** Thread slot in the thread table.  */

storage/innobase/log/log0log.cc

@@ -2,7 +2,7 @@
 
 Copyright (c) 1995, 2016, Oracle and/or its affiliates. All Rights Reserved.
 Copyright (c) 2009, Google Inc.
-Copyright (C) 2014, 2016, MariaDB Corporation. All Rights Reserved.
+Copyright (C) 2014, 2017, MariaDB Corporation. All Rights Reserved.
 
 Portions of this file contain modifications contributed and copyrighted by
 Google, Inc. Those modifications are gratefully acknowledged and are described
@@ -2552,6 +2552,10 @@ log_pad_current_log_block(void)
 		pad_length = 0;
 	}
 
+	if (pad_length) {
+		srv_stats.n_log_scrubs.inc();
+	}
+
 	for (i = 0; i < pad_length; i++) {
 		log_write_low(&b, 1);
 	}
@@ -2571,6 +2575,7 @@ void
 log_scrub()
 /*=========*/
 {
+	log_mutex_enter();
 	ulint cur_lbn = log_block_convert_lsn_to_no(log_sys->lsn);
 
 	if (next_lbn_to_pad == cur_lbn)
@@ -2579,6 +2584,7 @@ log_scrub()
 	}
 
 	next_lbn_to_pad = log_block_convert_lsn_to_no(log_sys->lsn);
+	log_mutex_exit();
 }
 
 /* log scrubbing speed, in bytes/sec */

storage/innobase/srv/srv0srv.cc

@@ -1705,6 +1705,7 @@ srv_export_innodb_status(void)
 		scrub_stat.page_split_failures_missing_index;
 	export_vars.innodb_scrub_page_split_failures_unknown =
 		scrub_stat.page_split_failures_unknown;
+	export_vars.innodb_scrub_log = srv_stats.n_log_scrubs;
 
 	mutex_exit(&srv_innodb_monitor_mutex);
 }