If this is not your root partition and your linux kernel is > 2.2.8 simply run the following:

1. unmount the partition you plan to work with (umount /dev/sdf)
2. # tune2fs -O extents,uninit_bg,dir_index /dev/sdf
3. #  e2fsck -pf /dev/sdf
4. modify /etc/fstab to say ext4 if you’re using fstab to mount the partition

Done!