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

   1 #!/bin/bash
   2 # Copyright (C) 2016 Ian Kelling
   3 #
   4 # Licensed under the Apache License, Version 2.0 (the "License");
   5 # you may not use this file except in compliance with the License.
   6 # You may obtain a copy of the License at
   7 #
   8 #     http://www.apache.org/licenses/LICENSE-2.0
   9 #
  10 # Unless required by applicable law or agreed to in writing, software
  11 # distributed under the License is distributed on an "AS IS" BASIS,
  12 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  13 # See the License for the specific language governing permissions and
  14 # limitations under the License.
  15
  16
  17 [[ $EUID == 0 ]] || exec sudo -E "${BASH_SOURCE[0]}" "$@"
  18
  19 source /usr/local/lib/err
  20
  21 shopt -s nullglob
  22
  23 usage() {
  24   cat <<EOF
  25 usage: $0 SUBVOL_MOUNTPOINT... | -p SUBVOL_PATH...
  26
  27 In git this is not not executable because it's meant to be installed
  28 using ./install-my-scripts
  29
  30 Print the unstale subvol name into /nocow/btrfs-stale/\$subvol
  31
  32 If latest subvols \$@ are not mounted, print a message to terminal.
  33
  34 Fresh is opposite of stale. To be fresh, either SUBVOL_MOUNTPOINT is a
  35 snapshot of the latest, or the latest snapshot is snapshot of
  36 SUBVOL_MOUNTPOINT.
  37
  38 -p            Args are SUBVOL_PATH, not mountpoints from which we derive
  39               that information.
  40 -v|--verbose  Be more verbose
  41 -h|--help  Print help and exit.
  42
  43 Note: Uses GNU getopt options parsing style
  44 EOF
  45   exit $1
  46 }
  47
  48 ##### begin command line parsing ########
  49
  50 subvol_path=false
  51 verbose=false
  52 temp=$(getopt -l help,verbose hpv "$@") || usage 1
  53 eval set -- "$temp"
  54 while true; do
  55   case $1 in
  56     -p) subvol_path=true ;;
  57     -v|--verbose) verbose=true ;;
  58     -h|--help) usage ;;
  59     --) shift; break ;;
  60     *) echo "$0: unexpected args: $*" >&2 ; usage 1 ;;
  61   esac
  62   shift
  63 done
  64
  65 if [[ ! $1 ]]; then
  66   echo "$0: error: expected mountpoint argument"
  67 fi
  68
  69 stale-file() {
  70   stale_dir=/nocow/btrfs-stale
  71   stale_file=$stale_dir/$vol
  72   if $stale; then
  73     mkdir -p $stale_dir
  74     printf "%s\n" $freshest_snap > $stale_file
  75   else
  76     rm -f $stale_file
  77   fi
  78
  79 }
  80 pre="check-subvol-stale:${SSH_CLIENT:+ $HOSTNAME:}"
  81
  82 d() {
  83   if $verbose; then
  84     printf "$pre %s\n" "$*"
  85   fi
  86 }
  87
  88 # duplicated in mount-latest-sub
  89 # Reassign $1 var from /dev/dm- to corresponding /dev/mapper/
  90 mapper-dev() {
  91   local mapdev
  92   local -n devref=$1
  93   if [[ $devref == /dev/dm-* ]]; then
  94     for mapdev in /dev/mapper/*; do
  95       if [[ $(readlink -f $mapdev) == "$devref" ]]; then
  96         devref=$mapdev
  97         break
  98       fi
  99     done
 100   fi
 101 }
 102 tmpf=$(mktemp)
 103 d tmpf=$tmpf
 104 for d; do
 105
 106   if $subvol_path; then
 107     svp=$d
 108     root_dir=${d%/*}
 109     subvol_dir=${d##*/}
 110     vol=$subvol_dir
 111   else
 112     vol=${d##*/}
 113     # second field, non-comment line == $d
 114     dev=$(sed -rn "s,^\s*([^#]\S*)\s+$d\s.*,\1,p" /etc/fstab /etc/mtab|head -n1)
 115
 116     d dev=$dev
 117     subvol_dir=$(sed -rn "s,^\s*[^#]\S*\s+$d\s.*\bsubvol=([a-zA-A/]+).*,\1,p" /etc/fstab /etc/mtab|head -n1)
 118     if [[ ! $subvol_dir ]]; then
 119       continue
 120     fi
 121     d subvol_dir=$subvol_dir
 122
 123     ### begin getting root_dir
 124     ### this is duplicated in mount-latest-subvol
 125     # note, we need $dev because $d might not be mounted, and we do this loop
 126     # because the device in fstab for the rootfs can be different.
 127     for devx in $(btrfs fil show $dev| sed -rn 's#.*path (\S+)$#\1#p'); do
 128       if [[ $devx == dm-* ]]; then
 129         devx=/dev/$devx
 130         d mapper-dev $devx
 131         mapper-dev devx
 132       fi
 133       d devx=$devx
 134       root_dir=$(sed -rn "s,^\s*$devx\s+(\S+).*\bsubvolid=[05]\b.*,\1,p" /etc/mtab /etc/fstab|head -n1)
 135       if [[ $root_dir ]]; then
 136         d root_dir=$root_dir
 137         break
 138       fi
 139     done
 140     if [[ ! $root_dir ]]; then
 141       echo "$0: error could not find root subvol mount for $dev" >&2
 142       exit 1
 143     fi
 144     ### end getting root_dir
 145     svp=$root_dir/$subvol_dir # subvolume path
 146     d "svp=$svp # subvolume path"
 147   fi
 148
 149   # note: relying on null glob
 150   ls_args=($root_dir/btrbk/$subvol_dir.20*)
 151   if (( ${#ls_args[@]} )); then
 152     # Assumes we are in the 21st century.
 153     ls -1dvrq $root_dir/btrbk/$subvol_dir.20* >$tmpf
 154     mapfile -t snaps <$tmpf
 155   else
 156     # no snapshots yet
 157     # TODO: make this an error and override with a cli flag
 158     echo "$0: warning: no snapshots found at $root_dir/btrbk/$subvol_dir.20*. this is expected for a brand new volume"
 159     continue
 160   fi
 161
 162   # last_snap by date.
 163   last_snap="${snaps[0]}"
 164
 165   case $last_snap in
 166     $root_dir/btrbk/$subvol_dir.20*) : ;;
 167     *)
 168       echo "$0: error: unexpected last_snap:$last_snap"
 169       exit 1
 170       ;;
 171   esac
 172
 173   d last_snap=$last_snap
 174   ## alternate slower alternative which would not rely on ls sorting:
 175   # last_snap=$(
 176   #   for s in ${snaps[@]}; do
 177   #     f=${s##*/}
 178   #     unix_time=$(date -d $(sed -r  's/(.{4})(..)(.{5})(..)(.*)/\1-\2-\3:\4:\5/' <<<${f#$vol.}) +%s)
 179   #     printf "%s %s\n" $unix_time $s # part of the pipeline
 180   #     # sort will fail
 181   #   done | sort -r | head -n 1 | awk '{print $2}' || [[ ${PIPESTATUS[1]} == 141 || ${PIPESTATUS[0]} == 32 ]]
 182   #          )
 183   # if [[ ! $last_snap ]]; then
 184   #   # should not happen.
 185   #   echo "$0: error: could not find latest snapshot for $svp among ${snaps[*]}" >&2
 186   #   exit 1
 187   # fi
 188
 189   if [[ ! -e $svp ]]; then
 190     echo "$0: warning: subvol does not exist: $svp"
 191     echo "$0 assuming this host was just for receiving and latest snap is freshest"
 192     freshest_snap=$last_snap
 193     stale=true
 194     stale-file
 195     continue
 196   fi
 197
 198   # get info on last received sub
 199   last_received=
 200   last_received_cgen=0
 201   for f in ${snaps[@]}; do
 202     show="$(btrfs sub show $f)"
 203     if echo "$show" | grep -E "Received UUID:\s+[[:alnum:]]" &>/dev/null; then
 204       d found received uuid in $f
 205       cgen=$(echo "$show" | sed -rn 's,^\s*Gen at creation:\s+([0-9]+).*,\1,p')
 206       if [[ $cgen -gt $last_received_cgen ]]; then
 207         last_received_cgen=$cgen
 208         last_received=$f
 209       elif [[ $last_received ]]; then
 210         # optimization: we are looking in reverse order by date, so if
 211         # we find one that has a lesser cgen, assume the rest will all
 212         # be lesser.
 213         break
 214       fi
 215     fi
 216   done
 217   d last_received_cgen=$last_received_cgen
 218   d last_received=$last_received
 219
 220
 221   # if there is a last_received, we can assume stale or fresh if we are newer/older
 222   if [[ $last_received ]]; then
 223     svp_cgen=$(btrfs sub show $svp | sed -rn 's,^\s*Gen at creation:\s+([0-9]+).*,\1,p')
 224     d svp_cgen=$svp_cgen
 225     if [[ $svp_cgen -ge $last_received_cgen ]]; then
 226       stale=false
 227     else
 228       d "$svp stale: it's gen at creation, $svp_cgen, is earlier than the last received snapshot, $last_received's gen at creation: $last_received_cgen"
 229       freshest_snap=$last_received
 230       stale=true
 231     fi
 232     stale-file
 233     continue
 234   fi
 235
 236   # fallback to using last_snap as the freshest
 237   freshest_snap=$last_snap
 238   stale=true
 239   # fresh if $svp has $last_snap as a snapshot,
 240   if btrfs sub show $svp 2>/dev/null | sed '0,/^\s*Snapshot(s):/d;s/^\s*//' | \
 241       grep -xF ${last_snap#"$root_dir"/} >/dev/null; then
 242     stale=false
 243   else # or else $svp is a snapshot of $last_snap. we use a uuid
 244     # comparison, which if I remember from the docs, is a bit more
 245     # robust, perhaps to renames.
 246     last_snap_uuid=$(btrfs sub show $last_snap| awk '$1 == "UUID:" {print $2}')
 247     if btrfs sub show $svp| grep "^\s*Parent UUID:\s*$last_snap_uuid$" &>/dev/null; then
 248       stale=false
 249     fi
 250   fi
 251
 252   stale-file
 253 done
 254 rm $tmpf