tinyramfs/storage-device

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2020-01-28 20:43:42 +05:30
#!/bin/sh
# Copyright (c) 2012-2019, Piotr Karbowski <piotr.karbowski@gmail.com>
# All rights reserved.
#
# Redistribution and use in source and binary forms, with or without modification, are
# permitted provided that the following conditions are met:
#
# * Redistributions of source code must retain the above copyright notice, this list
# of conditions and the following disclaimer.
# * Redistributions in binary form must reproduce the above copyright notice, this list
# of conditions and the following disclaimer in the documentation and/or other
# materials provided with the distribution.
# * Neither the name of the Piotr Karbowski nor the names of its contributors may be
# used to endorse or promote products derived from this software without specific
# prior written permission.
#
# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY
# EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
# MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL
# THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT
# OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
# INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
# LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE US
# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
# This script meant to create /dev/disk/by-* and /dev/mapper/* symlinks.
# and remove them after storage device is removed.
# the /dev/disk/by-* handling based on the idea and proof of concept from BitJam.
# debug
#exec >> /run/debug-mdev 2>&1
#set -x
#echo '### ENV:'
#env
#echo '### CODE:'
#
umask 077
storage_dir="/dev/.mdev-like-a-boss"
[ -d "${storage_dir}" ] || mkdir "${storage_dir}"
[ "${MDEV}" ] || exit 2
create_uuid_label_symlink() {
local target_dir="/dev/disk/by-${1}"
local target_symlink="${target_dir}/${2}"
[ -e "${target_symlink}" ] && return
mkdir -p "${target_dir}"
ln -snf "/dev/${MDEV}" "${target_symlink}"
echo "${target_symlink}" >"${storage_dir}/storage_symlink_${1}_${MDEV}"
}
add_symlinks() {
# Skip temp cryptsetup nodes.
case "${MDEV}" in
'dm-'[0-9]*)
case "$(cat "/sys/block/${MDEV}/dm/name")" in
'temporary-cryptsetup-'[0-9]*)
return 0
;;
esac
;;
esac
if command -v blkid >/dev/null 2>&1; then
local field name value UUID LABEL TYPE PTTYPE PARTUUID
local blkid_output="$(blkid "/dev/${MDEV}")"
eval "${blkid_output#*: }"
[ "${UUID}" ] && create_uuid_label_symlink 'uuid' "${UUID}"
[ "${LABEL}" ] && create_uuid_label_symlink 'label' "${LABEL}"
[ "${PARTUUID}" ] && create_uuid_label_symlink 'partuuid' "${PARTUUID}"
fi
if [ -f "/sys/block/${MDEV}/dm/name" ]; then
[ -d '/dev/mapper' ] || mkdir '/dev/mapper'
if ! [ -c '/dev/mapper/control' ]; then
awk '$2 == "device-mapper" { foo = system("mknod /dev/mapper/control c 10 " $1); exit foo }' /proc/misc || exit 1
fi
local dmname="$(cat "/sys/block/${MDEV}/dm/name")"
if [ "${dmname}" ]; then
local target_symlink="/dev/mapper/${dmname}"
[ -e "${target_symlink}" ] && return
ln -snf "/dev/${MDEV}" "${target_symlink}"
echo "${target_symlink}" >"${storage_dir}/storage_symlink_mapper_${MDEV}"
fi
fi
}
set_readahead() {
read_ahead_kb_control="/sys/class/block/${MDEV}/queue/read_ahead_kb"
new_read_ahead_kb="2048"
if [ -f "${read_ahead_kb_control}" ]; then
read_ahead_kb="$(cat "${read_ahead_kb_control}")"
if [ "${read_ahead_kb}" -lt "${new_read_ahead_kb}" ]; then
logger -t mdev "Changing ${MDEV} read_ahead_kb from ${read_ahead_kb} to ${new_read_ahead_kb}"
echo -n "${new_read_ahead_kb}" >"${read_ahead_kb_control}"
fi
fi
}
drop_symlinks() {
local type
for type in uuid label mapper; do
[ -f "${storage_dir}/storage_symlink_${type}_${MDEV}" ] || continue
local target_symlink="$(cat "${storage_dir}/storage_symlink_${type}_${MDEV}" 2>/dev/null)"
[ "${target_symlink}" ] || continue
local target_symlink_device="$(readlink "${target_symlink}")"
if [ "${target_symlink_device}" = "/dev/${MDEV}" ]; then
rm "${target_symlink}"
fi
rm "${storage_dir}/storage_symlink_${type}_${MDEV}"
done
}
case "${ACTION}" in
'add'|'')
add_symlinks
set_readahead
;;
'remove')
drop_symlinks
;;
esac