btrfs balance maintenance script

btrfs-maint

#!/bin/bash

### Configuration ##############################################################

services_to_stop=(
    backup.timer
)

services_to_wait_for=(
    backup.service
)

################################################################################

set -o pipefail

mapfile -t mountpoints < <(
    findmnt --types btrfs --nofsroot --noheading --output SOURCE |
        sort -u |
        while IFS= read -r device; do
            findmnt --source "$device" --output TARGET --noheading | head -1
        done
)

usage() {
    cat << EOF
Usage: ${0##*/} [scrub] [MOUNTPOINT [...]]
    Runs a sequence of btrfs balance operations.

    Filesystems to run on:
$(printf "      * %s\n" "${mountpoints[@]}")

    Services to stop or wait for:
$(printf "      * %s\n" "${services_to_stop[@]}" "${services_to_wait_for[@]}")

Options:
    scrub    Run a btrfs scrub as well.
EOF
}

for x; do
    if [[ $x = "scrub" ]]; then
        scrub=1
    elif [[ $x = /* ]]; then
        mount_args=1
    else
        usage
        exit 1
    fi
done

[[ $UID -ne 0 ]] && exec sudo "$0" "$@"

stopped_services=()

restart_services() {
    local unit
    for unit in "${stopped_services[@]}"; do
        if systemctl start "$unit"; then
            echo "Started '$unit'."
        else
            echo "Failed to start '$unit'!"
        fi
    done
}

trap 'echo -e "\nInterrupted!"; exit 1' INT TERM
trap 'restart_services' EXIT

for unit in "${services_to_stop[@]}"; do
    if systemctl status "$unit" &> /dev/null; then
        systemctl stop "$unit"
        echo "Stopped '$unit'."
        stopped_services+=("$unit")
    fi
done

for unit in "${services_to_wait_for[@]}"; do
    if systemctl status "$unit" &> /dev/null; then
        echo -n "Waiting for '$unit' to complete... "
        sleep 1
        while systemctl status "$unit" &> /dev/null; do
            sleep 1
        done
        echo "done."
    fi
done

die() {
    cat << EOF

  +----------------------+
  |  There were errors!  |
  +----------------------+

EOF
    exit 1
}

msg() {
    sed 's/^/  /'
}


for mount in "${mountpoints[@]}"; do
    if (( mount_args )); then
        skip_mount=1
        for x; do
            x="$(sed -r 's/\/{2,}/\//g; s/.\/$//' <<< "$x")"
            if [[ $x = $mount ]]; then
                skip_mount=0
            fi
        done
        if (( skip_mount )); then
            continue
        fi
    fi
    back="----------------------------------------"
    echo "== $mount ${back:${#mount}}"
    if (( scrub )); then
        echo "> Scrub..."
        # progress bar when running in a terminal
        if [[ -t 1 ]]; then
            while sleep 1; do
                btrfs scrub status "$mount" | 
                    perl -n0777e '
                        sub quit { print "  Cannot read scrub status!\e[K\r"; exit 1; }
                        my ($bytes, $progress) = /^bytes scrubbed:\s*(\S+)\s+.*?([\d.]+)%/im
                            or quit;
                        my ($timeleft) = /^time left:\s*(\S+)/im or quit;
                        my ($rate) = /^rate:\s*(.*)/im or quit;
                        $bytes =~ s{(\d+\.\d+)([GMKB])?}{
                            !$2 ? sprintf "%.1f ", $1 : sprintf "%.0f %s", $1, $2 }eg;
                        $rate =~ s{(\d+\.\d+)([MKB])?}{
                            !$2 ? sprintf "%.1f ", $1 : sprintf "%.0f %s", $1, $2 }eg;
                        my $width = 20;
                        my $bar = int($progress * $width / 100 + 0.5);
                        printf "  ETA: %s [%s>%s] %s, %s\e[K\r",
                            $timeleft,
                            "=" x $bar,
                            " " x ($width - $bar),
                            $bytes,
                            $rate;
                    '
            done &
            status=$(btrfs scrub start -B "$mount" 2>&1)
            error=$?
            kill %
            tput cr; tput el  # clear line
            msg <<< "$status"
            (( error )) && die
        else
            btrfs scrub start -B "$mount" |& msg || die
        fi
    fi
    #for x in 1 5 10 20 30; do
    for x in 0 5; do
        echo "> Metadata balancing, usage=$x..."
        btrfs balance start -musage="$x" "$mount" |& msg || die
    done
    #for x in 1 5 10 20 30 40 50; do
    for x in 0 5 10; do
        echo "> Data balancing, usage=$x..."
        btrfs balance start -dusage="$x" "$mount" |& msg || die
    done
done