1a - Remove mount point /btrfs/test of subvolume test on /dev/sdb1 (7.63 GiB) from /etc/fstab -> 1b
1b - Unmount subvolume test on /dev/sdb1 (7.63 GiB) at /btrfs/test -> 1c
1c - Delete subvolume test on /dev/sdb1 (7.63 GiB) ->
