#!/bin/bash
set -ex

DATA_DIR=/var/lib/containerd/devmapper
POOL_NAME=devpool

sudo mkdir -p ${DATA_DIR}

# Create data file
sudo touch "${DATA_DIR}/data"
sudo truncate -s 100G "${DATA_DIR}/data"

# Create metadata file
sudo touch "${DATA_DIR}/meta"
sudo truncate -s 10G "${DATA_DIR}/meta"

# Allocate loop devices
DATA_DEV=$(sudo losetup --find --show "${DATA_DIR}/data")
META_DEV=$(sudo losetup --find --show "${DATA_DIR}/meta")

# Define thin-pool parameters.
# See https://www.kernel.org/doc/Documentation/device-mapper/thin-provisioning.txt for details.
SECTOR_SIZE=512
DATA_SIZE="$(sudo blockdev --getsize64 -q ${DATA_DEV})"
LENGTH_IN_SECTORS=$(bc <<< "${DATA_SIZE}/${SECTOR_SIZE}")
DATA_BLOCK_SIZE=128
LOW_WATER_MARK=32768

# Create a thin-pool device
sudo dmsetup create "${POOL_NAME}" \
    --table "0 ${LENGTH_IN_SECTORS} thin-pool ${META_DEV} ${DATA_DEV} ${DATA_BLOCK_SIZE} ${LOW_WATER_MARK}"

cat << EOF
#
# Add this to your config.toml configuration file and restart the containerd daemon
#
[plugins]
  [plugins.devmapper]
    pool_name = "${POOL_NAME}"
    root_path = "${DATA_DIR}"
    base_image_size = "50GB"
    discard_blocks = true
EOF
