burrow-pi-img/scripts/qcow2_handling

# QCOW2 Routines

export CURRENT_IMAGE
export CURRENT_MOUNTPOINT

export NBD_DEV
export MAP_DEV

# set in build.sh
# should be fairly enough for the beginning
# overwrite here by uncommenting following lines
# BASE_QCOW2_SIZE=12G

init_nbd() {
    modprobe nbd max_part=16
    if [ -z "${NBD_DEV}" ]; then
	for x in /sys/class/block/nbd* ; do
	    S=`cat $x/size`
	    if [ "$S" == "0" ] ; then
		NBD_DEV=/dev/$(basename $x)
		MAP_DEV=/dev/mapper/$(basename $x)p1
		break
	    fi
	done
    fi
}

# mount qcow2 image: mount_image <image file> <mountpoint>
mount_qimage() {
    init_nbd
    qemu-nbd --discard=unmap -c $NBD_DEV "$1"
    kpartx -a $NBD_DEV
    mount $MAP_DEV "$2"
    CURRENT_IMAGE="$1"
    CURRENT_MOUNTPOINT="$2"
}
export -f mount_qimage

# umount qcow2 image: umount_image <current mountpoint>
umount_qimage() {
    while mount | grep -q "$1"; do
            local LOCS
            LOCS=$(mount | grep "$1" | cut -f 3 -d ' ' | sort -r)
            for loc in $LOCS; do
		    echo "$loc"
                    umount "$loc"
            done
    done
    qemu-nbd -d $NBD_DEV
    kpartx -d $NBD_DEV
}
export -f umount_qimage

# create base image / backing image / mount image
load_qimage() {
    if [ -z "${CURRENT_MOUNTPOINT}" ]; then
        if [ ! -d "${ROOTFS_DIR}" ]; then mkdir -p "${ROOTFS_DIR}"; fi

        if [ "${CLEAN}" = "1" ] && [ -f "${WORK_DIR}/image-${STAGE}.qcow2" ]; then rm -f "${WORK_DIR}/image-${STAGE}.qcow2"; fi

        if [ ! -f "${WORK_DIR}/image-${STAGE}.qcow2" ]; then
            pushd ${WORK_DIR} > /dev/null
	    init_nbd
            if [ -z "${PREV_STAGE}" ]; then
                qemu-img create -f qcow2 image-${STAGE}.qcow2 $BASE_QCOW2_SIZE
                qemu-nbd --discard=unmap -c $NBD_DEV image-${STAGE}.qcow2
		echo 'type=83' | sfdisk $NBD_DEV
                kpartx -a $NBD_DEV
                mkfs.ext4 $MAP_DEV
    	    else
		if [ ! -f "${WORK_DIR}/image-${PREV_STAGE}.qcow2" ]; then exit 1; fi
                qemu-img create -f qcow2 \
                    -o backing_file=${WORK_DIR}/image-${PREV_STAGE}.qcow2 \
                    ${WORK_DIR}/image-${STAGE}.qcow2
                qemu-nbd --discard=unmap -c $NBD_DEV image-${STAGE}.qcow2
                kpartx -a $NBD_DEV
            fi
            mount $MAP_DEV "${ROOTFS_DIR}"
	    CURRENT_IMAGE=${WORK_DIR}/image-${STAGE}.qcow2
	    CURRENT_MOUNTPOINT=${ROOTFS_DIR}
	    popd > /dev/null
	else
	    mount_qimage "${WORK_DIR}/image-${STAGE}.qcow2" "${ROOTFS_DIR}"
	fi
	echo "Current image in use: ${CURRENT_IMAGE} (MP: ${CURRENT_MOUNTPOINT})"
    fi
}
export -f load_qimage

# umount current image and refresh mount point env var
unload_qimage() {
    if [ ! -z "${CURRENT_MOUNTPOINT}" ]; then
        fstrim -v "${CURRENT_MOUNTPOINT}" || true
	umount_qimage "${CURRENT_MOUNTPOINT}"
        CURRENT_IMAGE=""
        CURRENT_MOUNTPOINT=""
    fi
}
export -f unload_qimage