I hit that rebalancing needs space (and therefore can ENOSPC) issue at work when trying to compile ZFS on CoreOS on Digital Ocean before CoreOS switched from bt

I hit that rebalancing needs space (and therefore can ENOSPC) issue at work when trying to compile ZFS on CoreOS on Digital Ocean before CoreOS switched from btrfs to ext4 and overlayfs. Getting ENOSPC on btrfs rebalance when you are seeing regular writes return ENOSPC is a really annoying problem.