MDEV-34713 Backup and restore mariadb_upgrade_info file

The mariadb_upgrade_info file was not being backed up during
mariadb-backup --backup, causing MariaDB to incorrectly prompt for
upgrade after restore.

Add mariadb_upgrade_info to the list of files backed up from the datadir
during backup operations, ensuring the upgrade state is preserved across
backup and restore cycles.

All new code of the whole pull request, including one or several files
that are that are either new files or modified ones, are contributed
under the BSD-new license. I am contributing on behalf of my employer
Amazon Web Services, Inc.

Author: FarihaIS

extra/mariabackup/backup_copy.cc

@@ -1519,6 +1519,9 @@ ibx_copy_incremental_over_full()
 		    !(ret = backup_files_from_datadir(ds_data,
 						      xtrabackup_incremental_dir,
 						      "aria_log")) ||
+		    !(ret = backup_files_from_datadir(ds_data,
+						      xtrabackup_incremental_dir,
+						      "mariadb_upgrade_info")) ||
 		    !(ret = backup_mroonga_files_from_datadir(ds_data,
 						      xtrabackup_incremental_dir)))
 			goto cleanup;

extra/mariabackup/xtrabackup.cc

@@ -5379,6 +5379,13 @@ class BackupStages {
                                 return false;
                         }
 
+                        if (!backup_files_from_datadir(backup_datasinks.m_data,
+                                                       fil_path_to_mysql_datadir,
+                                                       "mariadb_upgrade_info")) {
+                                msg("Error on root data dir files backup");
+                                return false;
+                        }
+
 			if (has_rocksdb_plugin()) {
 				rocksdb_create_checkpoint();
 			}

mysql-test/suite/mariabackup/full_backup.result

@@ -41,3 +41,19 @@ undo001
 undo002
 XA COMMIT 'zombie';
 DROP TABLE t;
+#
+# MDEV-34713: mariadb_upgrade_info should be backed up and restored
+#
+CREATE TABLE t2(i INT) ENGINE INNODB;
+INSERT INTO t2 VALUES(100);
+# xtrabackup backup
+# xtrabackup prepare
+# shutdown server
+# remove datadir
+# xtrabackup move back
+# restart: --innodb_undo_tablespaces=0
+FOUND 1 /^[0-9]+\.[0-9]+\.[0-9]+/ in mariadb_upgrade_info
+SELECT * FROM t2;
+i
+100
+DROP TABLE t2;

mysql-test/suite/mariabackup/full_backup.test

@@ -68,3 +68,41 @@ list_files $targetdir undo*;
 XA COMMIT 'zombie';
 DROP TABLE t;
 rmdir $targetdir;
+
+--echo #
+--echo # MDEV-34713: mariadb_upgrade_info should be backed up and restored
+--echo #
+
+CREATE TABLE t2(i INT) ENGINE INNODB;
+INSERT INTO t2 VALUES(100);
+
+let $_datadir=`SELECT @@datadir`;
+let $targetdir=$MYSQLTEST_VARDIR/tmp/backup_upgrade_info;
+
+--write_file $_datadir/mariadb_upgrade_info
+10.11.0-MariaDB
+EOF
+
+--echo # xtrabackup backup
+--disable_result_log
+exec $XTRABACKUP --defaults-file=$MYSQLTEST_VARDIR/my.cnf --backup --target-dir=$targetdir;
+--enable_result_log
+
+--file_exists $targetdir/mariadb_upgrade_info
+
+--echo # xtrabackup prepare
+--disable_result_log
+exec $XTRABACKUP --prepare --target-dir=$targetdir;
+--source include/restart_and_restore.inc
+--enable_result_log
+
+--file_exists $_datadir/mariadb_upgrade_info
+
+--let SEARCH_FILE=$_datadir/mariadb_upgrade_info
+--let SEARCH_PATTERN=^[0-9]+\.[0-9]+\.[0-9]+
+--source include/search_pattern_in_file.inc
+
+SELECT * FROM t2;
+DROP TABLE t2;
+--remove_file $_datadir/mariadb_upgrade_info
+rmdir $targetdir;