extents-to-remove

#!/bin/bash

# SPDX-FileCopyrightText: 2016-2020 Graham R. Cobb
# SPDX-License-Identifier: GPL-3.0-or-later
#
# Copyright (C) 2016 Graham R. Cobb
# Released under GPL V3.0 -- see LICENSE
#
# extents-to-remove [-s] <disk> <directory>...
#
# Generates the extent list of extents which will be removed from the disk if the named
# directory/ies are removed.
#
# Directory names must be relative to the named disk.
#
# If the -s option is specified then the resulting list is automatically sent to extents-size.
#
# Note: this script may take a long time as the extents list for the whole disk must be generated!
#
# Example: to find out how much space would be recovered by removing two directories from a disk
# you might use:
#
#	extents-to-remove -s /mnt/data some/directory some/other/directory
#

# Make sure errors are passed back
set -o pipefail

if [ "$1" = "-s" ]
then
    shift
    $0 "$@" | extents-size
    exit $?
fi

if [ $# -lt 1 ]
then
	echo "$0: Disk name is required" >&2
	echo "Usage: $0 [-s] <disk> <directory>..." >&2
	exit 1
fi

# Remove trailing slash
disk=${1%/}
shift

declare -a dirs
declare -a findargs

while [ $# -gt 0 ]
do
    # Remove any trailing slash
    dir="${1%/}"

    dirs[${#dirs[*]}]="$disk/$dir"
    
    findargs[${#findargs[*]}]="-path"
    findargs[${#findargs[*]}]="$disk/$dir"
    findargs[${#findargs[*]}]="-prune"
    findargs[${#findargs[*]}]="-o"

    shift
done

dirextents="$(mktemp)" || exit $?

#echo extents-list "${dirs[@]}"
extents-list "${dirs[@]}" >$dirextents
status=$?
if [ $status != 0 ] ; then rm $dirextents ; exit $status ; fi

remextents="$(mktemp)"
status=$?
if [ $status != 0 ] ; then rm $dirextents ; exit $status ; fi

#echo extents-list "$disk" "${findargs[@]}"
extents-list "$disk" "${findargs[@]}" >$remextents
status=$?
if [ $status != 0 ] ; then rm $dirextents ; rm $remextents ; exit $status ; fi

extents-difference $dirextents $remextents
status=$?
rm $dirextents $remextents
exit $status