#!/bin/bash
set -eu

backing_device=$(findmnt -vno SOURCE /sysroot)
echo "Backing device: ${backing_device}"

# Handling devicemapper targets is a whole other thing
case $backing_device in
    /dev/mapper/*) echo "Not growing $backing_device"; exit 0 ;;
esac

syspath=/sys/class/block/$(basename "${backing_device}")
if ! test -d "${syspath}"; then
    echo "failed to find backing device ${syspath}"; exit 1
fi



# Note that we expect that the rootfs is on a partition
partition=$(cat "${syspath}"/partition)

# Walk up to find the parent blockdev
parentpath=$(dirname "$(realpath "${syspath}")")
devmajmin=$(cat "${parentpath}"/dev)
parent="/dev/block/${devmajmin}"

# Grow the partition
tmpf=$(mktemp)
# Ignore errors because growpart exits 1 if nothing changed;
# we need to check the output for NOCHANGE:
if ! /usr/bin/growpart "${parent}" "${partition}" > "${tmpf}"; then
    cat "${tmpf}"
    if grep -qEe '^NOCHANGE: ' "${tmpf}"; then
        exit 0
    fi
    echo "growpart failed"
    exit 1
fi
cat "${tmpf}"
# Now, temporarily remount the sysroot writable in our mount namespace
mount -o remount,rw /sysroot
# And defer to systemd's growfs wrapper which handles dispatching on
# the target filesystem type.
/usr/lib/systemd/systemd-growfs /sysroot