Remove the journal feature from the file system (downgrade to ext2)

tune2fs -O ^has_journal /dev/sda8

fsck to delete the journal:

e2fsck -f /dev/sda8

recreate the journal (change back to ext3)

tune2fs -j /dev/sda8

and finally, remount it. On a live system, just reboot it.

Another option would be to change the partition to ext3 in /etc/fstab.