tinyramfs/storage-device

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#!/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
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# TODO use /tmp
storage_dir="/tmp/.mdev-like-a-boss"
[ -d "$storage_dir" ] || mkdir "$storage_dir"
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[ "$MDEV" ] || exit 2
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create_uuid_label_symlink() {
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target_dir="/dev/disk/by-${1}"
target_symlink="${target_dir}/${2}"
[ -e "$target_symlink" ] && return
mkdir -p "$target_dir"
ln -sf "/dev/${MDEV}" "$target_symlink"
printf "%s\n" "$target_symlink" > "${storage_dir}/storage_symlink_${1}_${MDEV}"
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}
add_symlinks() {
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# Skip temp cryptsetup nodes.
case "$MDEV" in
"dm-"[0-9]*)
case "$(cat "/sys/block/${MDEV}/dm/name")" in
"temporary-cryptsetup-"[0-9]*)
return 0
;;
esac
;;
esac
if command -v blkid > /dev/null 2>&1; then
blkid_output=$(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 " $1); exit foo }' /proc/misc || exit 1
while read -r dm; do
[ "${dm#* }" = device-mapper ] && {
mknod /dev/mapper/control c 10 "${dm% *}" || exit 1
}
done < /proc/misc
fi
dmname=$(cat "/sys/block/${MDEV}/dm/name")
if [ "$dmname" ]; then
target_symlink="/dev/mapper/${dmname}"
[ -e "$target_symlink" ] && return
ln -sf "/dev/${MDEV}" "$target_symlink"
printf "%s\n" "$target_symlink" > "${storage_dir}/storage_symlink_mapper_${MDEV}"
fi
fi
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}
set_readahead() {
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read_ahead_kb_control="/sys/class/block/${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 $new_read_ahead_kb"
printf "%s" "$new_read_ahead_kb" > "$read_ahead_kb_control"
fi
fi
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}
drop_symlinks() {
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for type in uuid label mapper; do
[ -f "${storage_dir}/storage_symlink_${type}_${MDEV}" ] || continue
target_symlink=$(cat "${storage_dir}/storage_symlink_${type}_${MDEV}" 2> /dev/null)
[ "$target_symlink" ] || continue
target_symlink_device=$(readlink "$target_symlink")
if [ "$target_symlink_device" = "/dev/${MDEV}" ]; then
rm "$target_symlink"
fi
rm "${storage_dir}/storage_symlink_${type}_${MDEV}"
done
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}
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case "$ACTION" in
add | "")
add_symlinks
set_readahead
;;
remove)
drop_symlinks
;;
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esac