Problem in import & expdp Dump file

Hi all,
i face a problem on (oracle database) installed on server Linux i need to export back as dump file, when i try to export give me the below error.

[root@srv1 mohamed]# expdp system/oracle directory=test dumpfile=Prodfb20150311.dmp logfile=Prodfb20150311.log FULL=y

Export: Release 11.2.0.1.0 - Production on Thu Mar 12 09:27:09 2015

Copyright (c) 1982, 2009, Oracle and/or its affiliates. All rights reserved.

Connected to: Oracle Database 11g Enterprise Edition Release 11.2.0.1.0 - 64bit Production
With the Partitioning, OLAP, Data Mining and Real Application Testing options
ORA-39002: invalid operation
ORA-39070: Unable to open the log file.
ORA-29283: invalid file operation
ORA-06512: at "SYS.UTL_FILE", line 536
ORA-29283: invalid file operation

the steps i had made on SQLpluse:

1-CREATE DIRECTORY test AS '/u01/backup/testdump';

GRANT read, write ON DIRECTORY test to system;

Does the OS-user the Oracle instance runs under have write permission on the directory?

oracle user can access /u01/backup/testdump & have permission to write on this path "i test create new file on this path by oracle user ""