While mouting NFS shares more than 200 times using a script, the error "mount.nfs: Input/output error" appears

Issue

When trying to mount and umount a NFS share around 200 times after few time, it gives error as follows.

    mount.nfs: Input/output error

The following script can be used to reproduce.

    for i in $(seq 1 1000); do echo "mount nb $i" ;mount /mount_point; echo "connection number" $(netstat -an | grep 2049| wc -l) ; umount /mount_point ; done

And the output will be as follows after some time.

connection number 392
mount nb 197
mount.nfs: Input/output error
connection number 393
umount: /mount_point: not mounted