It’s quite a while since the news on btrfs, Chris Mason is working on. Since Toei Rei offered her ebuilds for our Overlay, btrfs is even in use here and it has been proved, that there are no great problems. Today she told me some hint she picked up while talking to Chris Mason. For displaying the subvolumes on a partition, mount its subvolume ‘.’:
mount -t btrfs -o subvol=. /dev/xxx /mnt/btrfs
The mountpoint used above contains now a read-only filesystem, having the subvolumes as directories (which are writable then).