Is there a command to get the on-disk size of a btrfs subvolume?
The file system was mounted with -o compressed and the subvolume contains a lot of files that should compress rather well. I could use du on the root folder but then I will only get the sum of the uncompressed sizes and it is also relatively slow compared to a df-like command.
(Note: This question is not about the size of the unique data contained in this subvolume and how much it derived from other snapshots in a COW fashion.)