when i change my datadir, the server cannot restart anymore!!!

May 12 20:49:29 bogon systemd[1]: Starting MariaDB 10.3.14 database server...
May 12 20:49:29 bogon mysqld[21369]: 2019-05-12 20:49:29 0 [Note] /usr/sbin/mysqld (mysqld 10.3.14-MariaDB) starting as process 21369 ...
May 12 20:49:29 bogon systemd[1]: mariadb.service: main process exited, code=exited, status=1/FAILURE
May 12 20:49:29 bogon systemd[1]: Failed to start MariaDB 10.3.14 database server.
May 12 20:49:29 bogon systemd[1]: Unit mariadb.service entered failed state.
May 12 20:49:29 bogon systemd[1]: mariadb.service failed.
[root@bogon mariadb-10.3.14-rhel-7-x86_64-rpms]# systemctl start mariadb
Job for mariadb.service failed because the control process exited with error code. See "systemctl status mariadb.service" and "journalctl -xe" for details.
[root@bogon mariadb-10.3.14-rhel-7-x86_64-rpms]# systemctl status mariadb.service
● mariadb.service - MariaDB 10.3.14 database server
Loaded: loaded (/usr/lib/systemd/system/mariadb.service; enabled; vendor preset: disabled)
Drop-In: /etc/systemd/system/mariadb.service.d
└─dontprotecthome.conf, limitcore.conf, limitnofile.conf, migrated-from-my.cnf-settings.conf
Active: failed (Result: exit-code) since Sun 2019-05-12 20:50:21 CST; 5s ago
Docs: man:mysqld(8)
https://mariadb.com/kb/en/library/systemd/
Process: 21424 ExecStart=/usr/sbin/mysqld $MYSQLD_OPTS $_WSREP_NEW_CLUSTER $_WSREP_START_POSITION (code=exited, status=1/FAILURE)
Process: 21388 ExecStartPre=/bin/sh -c [ ! -e /usr/bin/galera_recovery ] && VAR= || VAR=`/usr/bin/galera_recovery`; [ $? -eq 0 ] && systemctl set-environment _WSREP_START_POSITION=$VAR || exit 1 (code=exited, status=0/SUCCESS)
Process: 21386 ExecStartPre=/bin/sh -c systemctl unset-environment _WSREP_START_POSITION (code=exited, status=0/SUCCESS)
Main PID: 21424 (code=exited, status=1/FAILURE)
Status: "MariaDB server is down"

May 12 20:50:20 bogon systemd[1]: Starting MariaDB 10.3.14 database server...
May 12 20:50:21 bogon mysqld[21424]: 2019-05-12 20:50:21 0 [Note] /usr/sbin/mysqld (mysqld 10.3.14-MariaDB) starting as process 21424 ...
May 12 20:50:21 bogon systemd[1]: mariadb.service: main process exited, code=exited, status=1/FAILURE
May 12 20:50:21 bogon systemd[1]: Failed to start MariaDB 10.3.14 database server.
May 12 20:50:21 bogon systemd[1]: Unit mariadb.service entered failed state.
May 12 20:50:21 bogon systemd[1]: mariadb.service failed.