I'm shredding files on large ext3 file systems (e.g. see this article for how I do this). In order to achieve this I need to mount the ext3 file systems without journaling. To most of them I get by with just unmounting them and re-mounting them as ext2. But some file systems can't be unmounted (e.g. /) and attempts to use "-o remount,data=writeback" fails with errors.
Is it possible to turn off journaling of a mounted ext3 file system without having to unmount it?