MDEV-13564 Mariabackup does not work with TRUNCATE

This is a merge from 10.2, but the 10.2 version of this will not
be pushed into 10.2 yet, because the 10.2 version would include
backports of MDEV-14717 and MDEV-14585, which would introduce
a crash recovery regression: Tables could be lost on
table-rebuilding DDL operations, such as ALTER TABLE,
OPTIMIZE TABLE or this new backup-friendly TRUNCATE TABLE.
The test innodb.truncate_crash occasionally loses the table due to
the following bug:

MDEV-17158 log_write_up_to() sometimes fails

extra/mariabackup/xtrabackup.cc

@@ -4081,9 +4081,6 @@ xtrabackup_backup_func()
 		goto log_fail;
 	}
 
-	ut_ad(!((log_sys.log.format ^ LOG_HEADER_FORMAT_CURRENT)
-		& ~LOG_HEADER_FORMAT_ENCRYPTED));
-
 	const byte* buf = log_sys.checkpoint_buf;
 
 reread_log_header:
@@ -4100,9 +4097,6 @@ xtrabackup_backup_func()
 		goto old_format;
 	}
 
-	ut_ad(!((log_sys.log.format ^ LOG_HEADER_FORMAT_CURRENT)
-		& ~LOG_HEADER_FORMAT_ENCRYPTED));
-
 	log_header_read(max_cp_field);
 
 	if (checkpoint_no_start != mach_read_from_8(buf + LOG_CHECKPOINT_NO)) {
@@ -4130,6 +4124,7 @@ xtrabackup_backup_func()
 	byte MY_ALIGNED(OS_FILE_LOG_BLOCK_SIZE) log_hdr[OS_FILE_LOG_BLOCK_SIZE];
 	memset(log_hdr, 0, sizeof log_hdr);
 	mach_write_to_4(LOG_HEADER_FORMAT + log_hdr, log_sys.log.format);
+	mach_write_to_4(LOG_HEADER_SUBFORMAT + log_hdr, log_sys.log.subformat);
 	mach_write_to_8(LOG_HEADER_START_LSN + log_hdr, checkpoint_lsn_start);
 	strcpy(reinterpret_cast<char*>(LOG_HEADER_CREATOR + log_hdr),
 	       "Backup " MYSQL_SERVER_VERSION);

mysql-test/suite/encryption/r/innodb_encrypt_log_corruption.result

@@ -125,13 +125,13 @@ WHERE engine = 'innodb'
 AND support IN ('YES', 'DEFAULT', 'ENABLED');
 COUNT(*)
 1
-FOUND 2 /InnoDB: Upgrading redo log:/ in mysqld.1.err
+FOUND 3 /InnoDB: Upgrading redo log:/ in mysqld.1.err
 # Minimal MariaDB 10.1.21 encrypted redo log
 SELECT COUNT(*) `1` FROM INFORMATION_SCHEMA.ENGINES WHERE engine='innodb'
 AND support IN ('YES', 'DEFAULT', 'ENABLED');
 1
 1
-FOUND 2 /InnoDB: Encrypting redo log/ in mysqld.1.err
+FOUND 1 /InnoDB: Encrypting redo log/ in mysqld.1.err
 ib_buffer_pool
 ib_logfile0
 ib_logfile1

mysql-test/suite/gcol/r/innodb_virtual_debug_purge.result

@@ -191,22 +191,18 @@ connection default;
 COMMIT;
 connect truncate,localhost,root,,;
 REPLACE INTO t1(pk, y) SELECT pk,y FROM t1;
-SET DEBUG_SYNC='row_trunc_before_dict_lock SIGNAL commit WAIT_FOR release';
 TRUNCATE TABLE t1;
 connection prevent_purge;
-SET DEBUG_SYNC='now WAIT_FOR commit';
 COMMIT;
 SET DEBUG_SYNC='now SIGNAL purge_start';
 disconnect prevent_purge;
 connection default;
 SET DEBUG_SYNC='now WAIT_FOR purge_start';
-InnoDB		2 transactions not purged
-SET DEBUG_SYNC='now SIGNAL release';
+InnoDB		0 transactions not purged
 SET GLOBAL debug_dbug=@old_dbug;
 connection truncate;
 disconnect truncate;
 connection default;
-InnoDB		0 transactions not purged
 DROP TABLE t1, t2;
 set debug_sync=reset;
 SET GLOBAL innodb_purge_rseg_truncate_frequency = @saved_frequency;

mysql-test/suite/gcol/t/innodb_virtual_debug_purge.test

@@ -240,29 +240,23 @@ COMMIT;
 
 connect(truncate,localhost,root,,);
 REPLACE INTO t1(pk, y) SELECT pk,y FROM t1;
-SET DEBUG_SYNC='row_trunc_before_dict_lock SIGNAL commit WAIT_FOR release';
 send TRUNCATE TABLE t1;
 
 connection prevent_purge;
-SET DEBUG_SYNC='now WAIT_FOR commit';
 COMMIT;
 SET DEBUG_SYNC='now SIGNAL purge_start';
 disconnect prevent_purge;
 
 connection default;
 SET DEBUG_SYNC='now WAIT_FOR purge_start';
-let $wait_all_purged=2;
 --source ../../innodb/include/wait_all_purged.inc
-let $wait_all_purged=0;
-SET DEBUG_SYNC='now SIGNAL release';
 SET GLOBAL debug_dbug=@old_dbug;
 
 connection truncate;
 reap;
 disconnect truncate;
 
 connection default;
---source ../../innodb/include/wait_all_purged.inc
 DROP TABLE t1, t2;
 
 --source include/wait_until_count_sessions.inc