MDEV-27343 Useless warning "InnoDB: Allocated tablespace ID <id> for...

MDEV-27343 Useless warning "InnoDB: Allocated tablespace ID <id> for <tablename>, old maximum was 0" during backup stage

mariabackup does not load dictionary during backup, but it loads
tablespaces, that is why fil_system.max_assigned_id is not set with
dict_check_tablespaces_and_store_max_id(). There is no sense to issue the
warning during backup.

mysql-test/suite/mariabackup/full_backup.result

 CREATE TABLE t(i INT) ENGINE INNODB;
 INSERT INTO t VALUES(1);
 # xtrabackup backup
+NOT FOUND /InnoDB: Allocated tablespace ID/ in backup.log
 INSERT INTO t VALUES(2);
 # xtrabackup prepare
 # shutdown server

mysql-test/suite/mariabackup/full_backup.test

@@ -4,11 +4,18 @@ CREATE TABLE t(i INT) ENGINE INNODB;
 INSERT INTO t VALUES(1);
 echo # xtrabackup backup;
 let $targetdir=$MYSQLTEST_VARDIR/tmp/backup;
+--let $backup_log=$MYSQLTEST_VARDIR/tmp/backup.log
 
 --disable_result_log
-exec $XTRABACKUP --defaults-file=$MYSQLTEST_VARDIR/my.cnf --backup --target-dir=$targetdir;
+exec $XTRABACKUP --defaults-file=$MYSQLTEST_VARDIR/my.cnf --backup --target-dir=$targetdir > $backup_log 2>&1;
 --enable_result_log
 
+# The following warning must not appear after MDEV-27343 fix
+--let SEARCH_PATTERN=InnoDB: Allocated tablespace ID
+--let SEARCH_FILE=$backup_log
+--source include/search_pattern_in_file.inc
+--remove_file $backup_log
+
 INSERT INTO t VALUES(2);
 
 

storage/innobase/fil/fil0fil.cc

@@ -1418,10 +1418,12 @@ fil_space_create(
 
 		if (!fil_system->space_id_reuse_warned) {
 			fil_system->space_id_reuse_warned = true;
-
-			ib::warn() << "Allocated tablespace ID " << id
-				<< " for " << name << ", old maximum was "
-				<< fil_system->max_assigned_id;
+			if (srv_operation != SRV_OPERATION_BACKUP) {
+				ib::warn() << "Allocated tablespace ID " << id
+					<< " for " << name
+					<< ", old maximum was "
+					<< fil_system->max_assigned_id;
+			}
 		}
 
 		fil_system->max_assigned_id = id;