guix system init with mounted btrfs subvolumes

[Matt Huszagh]

I'm encountering the error "rmdir: Device or resource busy" when I
attempt to perform guix system init on a mount point that has btrfs
subvolumes. Here's the process I've used for creating and mounting the
subvolumes prior to running `guix system init`:

mount -t btrfs -o compress=lzo LABEL=btrfs /mnt
btrfs subvolume create /mnt/@guixsd
btrfs subvolume create /mnt/@home
btrfs subvolume create /mnt/@snapshots
btrfs subvolume create /mnt/@grub
btrfs subvolume create /mnt/@guix
btrfs subvolume create /mnt/@gnu
umount /mnt
o_btrfs=defaults,X-mount.mkdir,compress=lzo,ssd,noatime
mount -o subvol=@guixsd,$o_btrfs LABEL=btrfs /mnt
mount -o subvol=@home,$o_btrfs LABEL=btrfs /mnt/home
mount -o subvol=@snapshots,$o_btrfs LABEL=btrfs /mnt/.snapshots
mount -o subvol=@grub,$o_btrfs LABEL=btrfs /mnt/boot/grub
mount -o subvol=@guix,$o_btrfs LABEL=btrfs /mnt/var/guix
mount -o subvol=@gnu,$o_btrfs LABEL=btrfs /mnt/gnu
mount -o X-mount.mkdir /dev/nvme0n1p1 /mnt/boot/efi

What have I done wrong here?

thx