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 d() {
  81   if $verbose; then
  82     printf "%s\n" "$*"
  83   fi
  84 }
  85
  86 # duplicated in mount-latest-sub
  87 # Reassign $1 var from /dev/dm- to corresponding /dev/mapper/
  88 mapper-dev() {
  89   local mapdev
  90   local -n devref=$1
  91   if [[ $devref == /dev/dm-* ]]; then
  92     for mapdev in /dev/mapper/*; do
  93       if [[ $(readlink -f $mapdev) == "$devref" ]]; then
  94         devref=$mapdev
  95         break
  96       fi
  97     done
  98   fi
  99 }
 100 tmpf=$(mktemp)
 101 d tmpf=$tmpf
 102 for d; do
 103
 104   if $subvol_path; then
 105     svp=$d
 106     root_dir=${d%/*}
 107     subvol_dir=${d##*/}
 108     vol=$subvol_dir
 109   else
 110     vol=${d##*/}
 111     # second field, non-comment line == $d
 112     dev=$(sed -rn "s,^\s*([^#]\S*)\s+$d\s.*,\1,p" /etc/fstab /etc/mtab|head -n1)
 113
 114     d dev=$dev
 115     subvol_dir=$(sed -rn "s,^\s*[^#]\S*\s+$d\s.*\bsubvol=([a-zA-A/]+).*,\1,p" /etc/fstab /etc/mtab|head -n1)
 116     if [[ ! $subvol_dir ]]; then
 117       continue
 118     fi
 119     d subvol_dir=$subvol_dir
 120
 121     ### begin getting root_dir
 122     ### this is duplicated in mount-latest-subvol
 123     # note, we need $dev because $d might not be mounted, and we do this loop
 124     # because the device in fstab for the rootfs can be different.
 125     for devx in $(btrfs fil show $dev| sed -rn 's#.*path (\S+)$#\1#p'); do
 126       if [[ $devx == dm-* ]]; then
 127         devx=/dev/$devx
 128         d mapper-dev $devx
 129         mapper-dev devx
 130       fi
 131       d devx=$devx
 132       root_dir=$(sed -rn "s,^\s*$devx\s+(\S+).*\bsubvolid=[05]\b.*,\1,p" /etc/mtab /etc/fstab|head -n1)
 133       if [[ $root_dir ]]; then
 134         d root_dir=$root_dir
 135         break
 136       fi
 137     done
 138     if [[ ! $root_dir ]]; then
 139       echo "$0: error could not find root subvol mount for $dev" >&2
 140       exit 1
 141     fi
 142     ### end getting root_dir
 143     svp=$root_dir/$subvol_dir # subvolume path
 144     d "svp=$svp # subvolume path"
 145   fi
 146
 147   # Assumes we are in the 21st century.
 148   ls -1dvrq $root_dir/btrbk/$subvol_dir.20* >$tmpf
 149   mapfile -t snaps <$tmpf
 150   if [[ ! ${snaps[*]} ]]; then
 151     # no snapshots yet
 152     # TODO: make this an error and override with a cli flag
 153     echo "$0: warning: no snapshots found at $root_dir/btrbk/$subvol_dir.20*. this is expected for a brand new volume"
 154     continue
 155   fi
 156
 157   # last_snap by date.
 158   last_snap="${snaps[0]}"
 159   ## alternate slower alternative which would not rely on ls sorting:
 160   # last_snap=$(
 161   #   for s in ${snaps[@]}; do
 162   #     f=${s##*/}
 163   #     unix_time=$(date -d $(sed -r  's/(.{4})(..)(.{5})(..)(.*)/\1-\2-\3:\4:\5/' <<<${f#$vol.}) +%s)
 164   #     printf "%s %s\n" $unix_time $s # part of the pipeline
 165   #     # sort will fail
 166   #   done | sort -r | head -n 1 | awk '{print $2}' || [[ ${PIPESTATUS[1]} == 141 || ${PIPESTATUS[0]} == 32 ]]
 167   #          )
 168   # if [[ ! $last_snap ]]; then
 169   #   # should not happen.
 170   #   echo "$0: error: could not find latest snapshot for $svp among ${snaps[*]}" >&2
 171   #   exit 1
 172   # fi
 173   d last_snap=$last_snap
 174
 175   if [[ ! -e $svp ]]; then
 176     echo "$0: warning: subvol does not exist: $svp"
 177     echo "$0 assuming this host was just for receiving and latest snap is freshest"
 178     freshest_snap=$last_snap
 179     stale=true
 180     stale-file
 181     continue
 182   fi
 183
 184   # get info on last received sub
 185   last_received=
 186   last_received_cgen=0
 187   for f in ${snaps[@]}; do
 188     show="$(btrfs sub show $f)"
 189     if echo "$show" | grep -E "Received UUID:\s+[[:alnum:]]" &>/dev/null; then
 190       d found received uuid in $f
 191       cgen=$(echo "$show" | sed -rn 's,^\s*Gen at creation:\s+([0-9]+).*,\1,p')
 192       if [[ $cgen -gt $last_received_cgen ]]; then
 193         last_received_cgen=$cgen
 194         last_received=$f
 195         elif [[ $last_received ]]; then
 196         # optimization: we are looking in reverse order by date, so if
 197         # we find one that has a lesser cgen, assume the rest will all
 198         # be lesser.
 199         break
 200       fi
 201     fi
 202   done
 203   d last_received_cgen=$last_received_cgen
 204   d last_received=$last_received
 205
 206
 207   # if there is a last_received, we can assume stale or fresh if we are newer/older
 208   if [[ $last_received ]]; then
 209     svp_cgen=$(btrfs sub show $svp | sed -rn 's,^\s*Gen at creation:\s+([0-9]+).*,\1,p')
 210     d svp_cgen=$svp_cgen
 211     if [[ $svp_cgen -ge $last_received_cgen ]]; then
 212       stale=false
 213     else
 214       d "$svp stale: it's gen at creation, $svp_cgen, is earlier than the last received snapshot, $last_received's gen at creation: $last_received_cgen"
 215       freshest_snap=$last_received
 216       stale=true
 217     fi
 218     stale-file
 219     continue
 220   fi
 221
 222   # fallback to using last_snap as the freshest
 223   freshest_snap=$last_snap
 224   stale=true
 225   # fresh if $svp has $last_snap as a snapshot,
 226   if btrfs sub show $svp 2>/dev/null | sed '0,/^\s*Snapshot(s):/d;s/^\s*//' | \
 227       grep -xF ${last_snap#"$root_dir"/} >/dev/null; then
 228     stale=false
 229   else # or else $svp is a snapshot of $last_snap. we use a uuid
 230     # comparison, which if I remember from the docs, is a bit more
 231     # robust, perhaps to renames.
 232     last_snap_uuid=$(btrfs sub show $last_snap| awk '$1 == "UUID:" {print $2}')
 233     if btrfs sub show $svp| grep "^\s*Parent UUID:\s*$last_snap_uuid$" &>/dev/null; then
 234       stale=false
 235     fi
 236   fi
 237
 238   stale-file
 239 done
 240 rm $tmpf