BTW: From FreeBSD I know gjournal, and thanks to the GEOM framework, it is easy to stack:

https://www.freebsd.org/doc/en/books/handbook/geom-gjournal.html
https://www.freebsd.org/cgi/man.cgi?query=gjournal&sektion=8&apropos=0&manpath=FreeBSD+10.2-RELEASE

In Linuxland seems to be JBD but is it that easy to apply or only through extensive programming?

Regards

Peter

P.S. Sorry about my enlightment spelling. I got enlightened;-)