If you have a external hdd or flash drive that can hold the files on your luks partition, I would recommend creating a tarball of that filesystem with something like this from a Ubuntu liveCD(as root)...
Then you could delete the partition and create a new one that fills up the space and once you do that you re-create the luks partition using the name uuid and then re-create the filesystem using its uuid and name.
tar -cvzpf /media/ExternalHdd/fs.tar.gz *
blkid > /media/ExternalHdd/fsuuids.txt
Then it is as simple as
tar -xvzpf /media/ExternalHdd/fs.tar.gz -C /media/encryptedfs/