iankelling.org Git - distro-setup/blob - check-subvol-stale

   1 #!/bin/bash
   2 # I, Ian Kelling, follow the GNU license recommendations at
   3 # https://www.gnu.org/licenses/license-recommendations.en.html. They
   4 # recommend that small programs, < 300 lines, be licensed under the
   5 # Apache License 2.0. This file contains or is part of one or more small
   6 # programs. If a small program grows beyond 300 lines, I plan to switch
   7 # its license to GPL.
   8
   9 # Copyright 2024 Ian Kelling
  10
  11 # Licensed under the Apache License, Version 2.0 (the "License");
  12 # you may not use this file except in compliance with the License.
  13 # You may obtain a copy of the License at
  14
  15 #     http://www.apache.org/licenses/LICENSE-2.0
  16
  17 # Unless required by applicable law or agreed to in writing, software
  18 # distributed under the License is distributed on an "AS IS" BASIS,
  19 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  20 # See the License for the specific language governing permissions and
  21 # limitations under the License.
  22
  23
  24
  25 [[ $EUID == 0 ]] || exec sudo -E "${BASH_SOURCE[0]}" "$@"
  26
  27 set -e; . /usr/local/lib/bash-bear; set +e
  28
  29 shopt -s nullglob
  30
  31 usage() {
  32   cat <<EOF
  33 usage: $0 SUBVOL_MOUNTPOINT... | -p SUBVOL_PATH...
  34
  35 In git this is not not executable because it's meant to be installed
  36 using ./install-my-scripts
  37
  38 Print the unstale subvol name into /nocow/btrfs-stale/\$subvol
  39
  40 If latest subvols \$@ are not mounted, print a message to terminal.
  41
  42 Fresh is opposite of stale. To be fresh, either SUBVOL_MOUNTPOINT is a
  43 snapshot of the latest, or the latest snapshot is snapshot of
  44 SUBVOL_MOUNTPOINT.
  45
  46 -p            Args are SUBVOL_PATH, not mountpoints from which we derive
  47               that information.
  48 -v|--verbose  Be more verbose
  49 -h|--help  Print help and exit.
  50
  51 Note: Uses GNU getopt options parsing style
  52 EOF
  53   exit $1
  54 }
  55
  56 ##### begin command line parsing ########
  57
  58 subvol_path=false
  59 verbose=false
  60 temp=$(getopt -l help,verbose hpv "$@") || usage 1
  61 eval set -- "$temp"
  62 while true; do
  63   case $1 in
  64     -p) subvol_path=true ;;
  65     -v|--verbose) verbose=true ;;
  66     -h|--help) usage ;;
  67     --) shift; break ;;
  68     *) echo "$0: unexpected args: $*" >&2 ; usage 1 ;;
  69   esac
  70   shift
  71 done
  72
  73 if [[ ! $1 ]]; then
  74   echo "$0: error: expected mountpoint argument"
  75 fi
  76
  77 stale-file() {
  78   stale_dir=/nocow/btrfs-stale
  79   stale_file=$stale_dir/$vol
  80   if $stale; then
  81     mkdir -p $stale_dir
  82     printf "%s\n" $freshest_snap > $stale_file
  83   else
  84     rm -f $stale_file
  85   fi
  86
  87 }
  88 pre="check-subvol-stale:${SSH_CLIENT:+ $HOSTNAME:}"
  89
  90 d() {
  91   if $verbose; then
  92     printf "$pre %s\n" "$*"
  93   fi
  94 }
  95
  96 # duplicated in mount-latest-sub
  97 # Reassign $1 var from /dev/dm- to corresponding /dev/mapper/
  98 mapper-dev() {
  99   local mapdev
 100   local -n devref=$1
 101   if [[ $devref == /dev/dm-* ]]; then
 102     for mapdev in /dev/mapper/*; do
 103       if [[ $(readlink -f $mapdev) == "$devref" ]]; then
 104         devref=$mapdev
 105         break
 106       fi
 107     done
 108   fi
 109 }
 110 tmpf=$(mktemp)
 111 d tmpf=$tmpf
 112 for d; do
 113
 114   if $subvol_path; then
 115     svp=$d
 116     root_dir=${d%/*}
 117     subvol_dir=${d##*/}
 118     vol=$subvol_dir
 119   else
 120     vol=${d##*/}
 121     # second field, non-comment line == $d
 122     dev=$(sed -rn "s,^\s*([^#]\S*)\s+$d\s.*,\1,p" /etc/fstab /etc/mtab|head -n1)
 123
 124     d dev=$dev
 125     subvol_dir=$(sed -rn "s,^\s*[^#]\S*\s+$d\s.*\bsubvol=([a-zA-A/]+).*,\1,p" /etc/fstab /etc/mtab|head -n1)
 126     if [[ ! $subvol_dir ]]; then
 127       continue
 128     fi
 129     d subvol_dir=$subvol_dir
 130
 131     ### begin getting root_dir
 132     ### this is duplicated in mount-latest-subvol
 133     # note, we need $dev because $d might not be mounted, and we do this loop
 134     # because the device in fstab for the rootfs can be different.
 135     for devx in $(btrfs fil show $dev| sed -rn 's#.*path (\S+)$#\1#p'); do
 136       if [[ $devx == dm-* ]]; then
 137         devx=/dev/$devx
 138         d mapper-dev $devx
 139         mapper-dev devx
 140       fi
 141       d devx=$devx
 142       root_dir=$(sed -rn "s,^\s*$devx\s+(\S+).*\bsubvolid=[05]\b.*,\1,p" /etc/mtab /etc/fstab|head -n1)
 143       if [[ $root_dir ]]; then
 144         d root_dir=$root_dir
 145         break
 146       fi
 147     done
 148     if [[ ! $root_dir ]]; then
 149       echo "$0: error could not find root subvol mount for $dev" >&2
 150       exit 1
 151     fi
 152     ### end getting root_dir
 153     svp=$root_dir/$subvol_dir # subvolume path
 154     d "svp=$svp # subvolume path"
 155   fi
 156
 157   # note: relying on null glob
 158   ls_args=($root_dir/btrbk/$subvol_dir.20*)
 159   if (( ${#ls_args[@]} )); then
 160     # Assumes we are in the 21st century.
 161     ls -1dvrq $root_dir/btrbk/$subvol_dir.20* >$tmpf
 162     mapfile -t snaps <$tmpf
 163   else
 164     # no snapshots yet
 165     # TODO: consider making this an error and override with a cli flag
 166     echo "$0: warning: no snapshots found at $root_dir/btrbk/$subvol_dir.20*. this is expected for a brand new volume"
 167     continue
 168   fi
 169
 170   # last_snap by date.
 171   last_snap="${snaps[0]}"
 172
 173   case $last_snap in
 174     $root_dir/btrbk/$subvol_dir.20*) : ;;
 175     *)
 176       echo "$0: error: unexpected last_snap:$last_snap"
 177       exit 1
 178       ;;
 179   esac
 180
 181   d last_snap=$last_snap
 182   ## alternate slower alternative which would not rely on ls sorting:
 183   # last_snap=$(
 184   #   for s in ${snaps[@]}; do
 185   #     f=${s##*/}
 186   #     unix_time=$(date -d $(sed -r  's/(.{4})(..)(.{5})(..)(.*)/\1-\2-\3:\4:\5/' <<<${f#$vol.}) +%s)
 187   #     printf "%s %s\n" $unix_time $s # part of the pipeline
 188   #     # sort will fail
 189   #   done | sort -r | head -n 1 | awk '{print $2}' || [[ ${PIPESTATUS[1]} == 141 || ${PIPESTATUS[0]} == 32 ]]
 190   #          )
 191   # if [[ ! $last_snap ]]; then
 192   #   # should not happen.
 193   #   echo "$0: error: could not find latest snapshot for $svp among ${snaps[*]}" >&2
 194   #   exit 1
 195   # fi
 196
 197   if [[ ! -e $svp ]]; then
 198     echo "$0: warning: subvol does not exist: $svp"
 199     echo "$0 assuming this host was just for receiving and latest snap is freshest"
 200     freshest_snap=$last_snap
 201     stale=true
 202     stale-file
 203     continue
 204   fi
 205
 206   # get info on last received sub
 207   last_received=
 208   last_received_cgen=0
 209   for f in ${snaps[@]}; do
 210     show="$(btrfs sub show $f)"
 211     if echo "$show" | grep -E "Received UUID:\s+[[:alnum:]]" &>/dev/null; then
 212       d found received uuid in $f
 213       cgen=$(echo "$show" | sed -rn 's,^\s*Gen at creation:\s+([0-9]+).*,\1,p')
 214       if [[ $cgen -gt $last_received_cgen ]]; then
 215         last_received_cgen=$cgen
 216         last_received=$f
 217       elif [[ $last_received ]]; then
 218         # optimization: we are looking in reverse order by date, so if
 219         # we find one that has a lesser cgen, assume the rest will all
 220         # be lesser.
 221         break
 222       fi
 223     fi
 224   done
 225   d last_received_cgen=$last_received_cgen
 226   d last_received=$last_received
 227
 228
 229   # if there is a last_received, we can assume stale or fresh if we are newer/older
 230   if [[ $last_received ]]; then
 231     svp_cgen=$(btrfs sub show $svp | sed -rn 's,^\s*Gen at creation:\s+([0-9]+).*,\1,p')
 232     d svp_cgen=$svp_cgen
 233     if [[ $svp_cgen -ge $last_received_cgen ]]; then
 234       stale=false
 235     else
 236       d "$svp stale: it's gen at creation, $svp_cgen, is earlier than the last received snapshot, $last_received's gen at creation: $last_received_cgen"
 237       freshest_snap=$last_received
 238       stale=true
 239     fi
 240     stale-file
 241     continue
 242   fi
 243
 244   # fallback to using last_snap as the freshest
 245   freshest_snap=$last_snap
 246   stale=true
 247   # fresh if $svp has $last_snap as a snapshot,
 248   if btrfs sub show $svp 2>/dev/null | sed '0,/^\s*Snapshot(s):/d;s/^\s*//' | \
 249       grep -xF ${last_snap#"$root_dir"/} >/dev/null; then
 250     stale=false
 251   else # or else $svp is a snapshot of $last_snap. we use a uuid
 252     # comparison, which if I remember from the docs, is a bit more
 253     # robust, perhaps to renames.
 254     last_snap_uuid=$(btrfs sub show $last_snap| awk '$1 == "UUID:" {print $2}')
 255     if btrfs sub show $svp| grep "^\s*Parent UUID:\s*$last_snap_uuid$" &>/dev/null; then
 256       stale=false
 257     fi
 258   fi
 259
 260   stale-file
 261 done
 262 rm $tmpf