MDEV-20060: Failing assertion: srv_log_file_size <= 512ULL << 30 while preparing backup

The general reason why innodb redo log file is limited by 512G is that
log_block_convert_lsn_to_no() returns value limited by 1G. But there is no
need to have unique log block numbers in log group. The fix removes 512G
limit and limits log group size by
(uint32_t maximum value) * (minimum page size), which, in turns, can be
removed if fil_io() is no longer used for innodb redo log io.

mysql-test/suite/mariabackup/big_innodb_log.test

@@ -0,0 +1,87 @@
+# The general reason why innodb redo log file is limited by 512G is that
+# log_block_convert_lsn_to_no() returns value limited by 1G. But there is no
+# need to have unique log block numbers in log group. This test forces innodb
+# to generate redo log files with non-unique log block numbers and tests
+# recovery process with such numbers.
+--source include/have_innodb.inc
+--source include/have_debug.inc
+
+--let MYSQLD_DATADIR= `select @@datadir`
+let $MYSQLD_BOOTSTRAP_CMD= $MYSQLD_BOOTSTRAP_CMD --datadir=$MYSQLD_DATADIR --debug-dbug=+d,innodb_small_log_block_no_limit;
+
+--source include/kill_mysqld.inc
+--rmdir $MYSQLD_DATADIR
+--mkdir $MYSQLD_DATADIR
+--mkdir $MYSQLD_DATADIR/mysql
+--mkdir $MYSQLD_DATADIR/test
+--exec $MYSQLD_BOOTSTRAP_CMD < $MYSQL_BOOTSTRAP_SQL_FILE >> $MYSQLTEST_VARDIR/tmp/bootstrap.log 2>&1
+let $old_restart_parameters=$restart_parameters;
+let $restart_parameters= $old_restart_parameters --debug-dbug=+d,innodb_small_log_block_no_limit;
+--source include/start_mysqld.inc
+
+CREATE TABLE t(i INT) ENGINE InnoDB;
+INSERT INTO t VALUES
+  (0), (1), (2), (3), (4), (5), (6), (7), (8), (9),
+  (0), (1), (2), (3), (4), (5), (6), (7), (8), (9),
+  (0), (1), (2), (3), (4), (5), (6), (7), (8), (9),
+  (0), (1), (2), (3), (4), (5), (6), (7), (8), (9),
+  (0), (1), (2), (3), (4), (5), (6), (7), (8), (9),
+  (0), (1), (2), (3), (4), (5), (6), (7), (8), (9),
+  (0), (1), (2), (3), (4), (5), (6), (7), (8), (9),
+  (0), (1), (2), (3), (4), (5), (6), (7), (8), (9),
+  (0), (1), (2), (3), (4), (5), (6), (7), (8), (9),
+  (0), (1), (2), (3), (4), (5), (6), (7), (8), (9);
+
+--let after_copy_test_t=BEGIN NOT ATOMIC INSERT INTO test.t SELECT * FROM test.t; UPDATE test.t SET i = 10 WHERE i = 0; DELETE FROM test.t WHERE i = 1; END
+
+--echo # xtrabackup backup, execute the following query after test.t is copied:
+--echo # $after_copy_test_t
+let $targetdir=$MYSQLTEST_VARDIR/tmp/backup;
+
+--disable_result_log
+exec $XTRABACKUP --defaults-file=$MYSQLTEST_VARDIR/my.cnf --backup --parallel=10 --target-dir=$targetdir --dbug=+d,mariabackup_events,innodb_small_log_block_no_limit;
+--enable_result_log
+
+--let $total_before=`SELECT count(*) FROM t`
+SELECT count(*) FROM t WHERE i = 0;
+--let $updated_before=`SELECT count(*) FROM t WHERE i = 10`
+
+echo # xtrabackup prepare;
+--disable_result_log
+exec $XTRABACKUP  --prepare --target-dir=$targetdir --dbug=+d,innodb_small_log_block_no_limit;
+--source include/restart_and_restore.inc
+--enable_result_log
+
+--let $total_after=`SELECT count(*) FROM t`
+SELECT count(*) FROM t WHERE i = 0;
+--let $updated_after=`SELECT count(*) FROM t WHERE i = 10`
+
+if ($total_before == $total_after) {
+--echo Ok
+}
+if ($total_before != $total_after) {
+--echo Failed
+}
+if ($updated_before == $updated_after) {
+--echo Ok
+}
+if ($updated_before != $updated_after) {
+--echo Failed
+}
+
+DROP TABLE t;
+rmdir $targetdir;
+--source include/kill_mysqld.inc
+--rmdir $MYSQLD_DATADIR
+
+perl;
+use lib "lib";
+use My::File::Path;
+my $install_db_dir = ($ENV{MTR_PARALLEL} == 1) ?
+  "$ENV{'MYSQLTEST_VARDIR'}/install.db" :
+  "$ENV{'MYSQLTEST_VARDIR'}/../install.db";
+copytree($install_db_dir, $ENV{'MYSQLD_DATADIR'});
+EOF
+
+--let $restart_parameters= $old_restart_parameters
+--source include/start_mysqld.inc