Comment # 5 on bug 1205740 from William Brown

How am I thinking of this wrong? 

btrfs fi show displays:

Label: none  uuid: cfa4961a-bb45-4941-ae70-948bb27fdd9b
    Total devices 1 FS bytes used 64.52GiB
    devid    1 size 256.00GiB used 106.06GiB path /dev/nvme0n1p2

It's not listing all the filesystems/subvolumes here. So when I go to
administer "that filesystem (rather, volume group)" why should it fail because
a subvolume is readonly. But instead of taking a filesystem id or similar,
btrfs expects a subvolume mountpoint, and is incorrectly saying that it can't
be administered because the *subvolume* is read-only. There is nothing stopping
administration of the fs, only a need to find a read-write subvolume.

That's extremely counter intuitive.