Comment # 2 on bug 1174939 from William Brown

pyrite# snapper setup-quota
Quota error (qgroup already set).

pyrite# snapper list
   # | Type   | Pre # | Date                             | User | Cleanup |
Description             | Userdata
-----+--------+-------+----------------------------------+------+---------+-------------------------+--------------
  0  | single |       |                                  | root |         |
current                 |
... <snip>

It appears quota is "already setup", but snapper list still shows it as
missing.

dmesg however says:

[19066.608743] BTRFS warning (device vda2): qgroup rescan init failed, qgroup
is not enabled

The btrfs has no cli to display quota status:

pyrite# btrfs quota --help
usage: btrfs quota <command> [options] <path>

    btrfs quota enable <path>
        Enable subvolume quota support for a filesystem.
    btrfs quota disable <path>
        Disable subvolume quota support for a filesystem.
    btrfs quota rescan [-sw] <path>
        Trash all qgroup numbers and scan the metadata again with the current
config.

manage filesystem quota settings

All of these commands appear to manipulate quota, and due to the layout of
subvolumes in transactional server "path" could be a subvol or the filesystem
and I'm honestly not sure (which is a usability problem in itself). I am
hesitant to start running these commands as I could make the problem worse.