make snapshot main volume, delete all others?

[Michael Kofler <michael@kofler.info>]

Fedora provides yum-fs-snapshot. If installed, on each package 
installation or update a snapshot of all btrfs filesystems is taken, so 
it is possible to revert the installation/update.

Suppose an update failed and I want to get back: with

# btrfs subvolume set-default yum-snapshot-whatever /

I define which snapshot to use at the next boot.

After rebooting I decide I really want to stay with this snapshot. I can 
delete all other snapshots, but can I also delete my previous main 
volume, thus defining the current default snapshot as my new base. (If 
not, a growing part of the filesystem is wasted for old data I don't 
need anymore.)

Any insight is appreciated!

	Michael Kofler