I'm unable to rebuild a Docker image on Leap 42.2, and getting random messages
about no space left on the device.

e.g. zypper operation like:

>>> Overall download size: 176.4 MiB. Already cached: 0 B. After the operation, additional 808.8 MiB will be used.

ends up with an error

>>> ApplyLayer exit status 1 stdout:  stderr: open /lib/modules/4.4.72-18.12-default/kernel/drivers/pci/host/pci-hyperv.ko: no space left on device
Unable to find image 'test_opensuse:0.1' locally

I checked, with btrfs utility and it turns out I have about 6GB of free space
left.

$ sudo btrfs fi df /var/lib/docker/btrfs
Data, single: total=12.01GiB, used=6.08GiB
System, single: total=4.00MiB, used=16.00KiB
Metadata, single: total=1.25GiB, used=293.75MiB
GlobalReserve, single: total=22.30MiB, used=0.00B

Everything was working last time I tried, about a month ago. Tried removing
snapper snapshots and btrfs rebalancing, didn't help, so I would guess it's a
bug where btrfs reports no space left to docker.