1. Creating snapshots fails

    One reason for this to happen is that there is an active swapfile on the btrfs subvolume being snapshotted. That is not supported by btrfs.

    In that case /var/log/snapper.log shows the error:

    create snapshot failed, ioctl(BTRFS_IOC_SNAP_CREATE_V2) failed, errno:26 (Text file busy)

    dmesg shows the warning:

    cannot snapshot subvolume with active swapfile

    A solution is to create a separate subvolume for the swapfile.