sst hang when the network fs mount at / hang

I have a three-node mariadb cluster. The cluster mount a network file system to the /iffs directory. When the network file system is abnormal, reading and writing /iffs and command df and so on will hang。And mariadb sst will also hang, because rsync is used for data synchronization in the wsrep_sst_rsync script, the "-f '//'" filter rule is specified in the filter condition, which will cause the rsync command to fail to complete.Once I delete the "-f '//'" rule, the sync completes quickly.