[Fedora-spins] Are we going to want to change live images to use overlayfs?

[Bruno Wolff III]

While not a done deal just yet, there is a pull request for overlayfs for 
3.18 that is likely to be accepted.

Live images currently use dm to do overlays, but this scheme fails badly 
when the overlay space files up. overlayfs looks like it will fail more 
gracefully when the upper filesystem fills up.

Is changing over to using overlayfs for live images something we'd want to 
look at for f22?

Are there advantages to using dm over overlayfs? (For example in theory, 
dm could be more space efficient by replacing just changed blocks rather 
than whole files, but I am not sure that significant space would be
saved in practice.)