Converting ext2 to ext4

I have a file-server with three disk's that are ext2 file-systems, is it possible to change/convert these to ext4 which have much improved characteristics, while data is on the disk's and without data-loss? If so, how is that accomplished? My system is Debian Wheezy, and I use lvm. I've found this , but I don't know if it is relevant for ext2 to ext4, does this work for me?