thinpool_migrator/init/lvm-migration-trim.conf

# Copyright 2024 The ChromiumOS Authors
# Use of this source code is governed by a BSD-style license that can be
# found in the LICENSE file.

description     "LVM migration to reclaim space for thinpool"
author          "chromium-os-dev@chromium.org"

start on stopped startup
stop on stopping system-services
task

# The job can be later restarted.
oom score -100

env VPD_MIGRATION_STATUS=/sys/firmware/vpd/rw/thinpool_migration_status

script
  get_volume_group() {
    local physical_volume="$1"

    pvs --reportformat json --readonly -o vg_name "${physical_volume}" \
        | jq .report[0].pv[0].vg_name
  }

  if ! [ -f "${VPD_MIGRATION_STATUS}" ]; then
    stop
    exit 0
  fi

  # Example root dev types we need to handle: /dev/sda2 -> /dev/sda,
  # /dev/mmcblk0p0 -> /dev/mmcblk0p, /dev/ubi2_1 -> /dev/ubi
  STATE_DEV="$(rootdev -s | sed 's/[0-9_]*$//')1"

  VG_NAME="$(get_volume_group "${STATE_DEV}")"

  if ! [ -n "${VG_NAME}" ]; then
    stop
    exit 0
  fi

  # Disable passdowns for the duration of this script: this speeds up the
  # reclaim process by ~30%.
  lvchange --discards nopassdown "${VG_NAME}/thinpool"

  # Add ionice to ensure that we don't overwhelm the system with discards.
  ionice -c 3 -- fstrim /mnt/stateful_partition

  lvchange --discards passdown "${VG_NAME}/thinpool"

  # Cleanup ensures that we will only trim the stateful logical volume
  # once post migration.
  thinpool_migrator --cleanup

  logger -t "${UPSTART_JOB}" "LVM migration finalized"
end script