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" "$@"
  18
  19 set -eE -o pipefail
  20 trap 'echo "$0:$LINENO:error: \"$BASH_COMMAND\" returned $?" >&2' ERR
  21
  22 shopt -s nullglob
  23
  24 usage() {
  25   cat <<EOF
  26 usage: $0 SUBVOL_MOUNTPOINT...
  27
  28 In git this is not not executable because it's meant to be installed
  29 using ./install-my-scripts
  30
  31 If latest subvols \$@ are not mounted, print a message, and print
  32 the unstale subvol name into /nocow/btrfs-stale/\$subvol
  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 -d         Enable debug output
  39 -h|--help  Print help and exit.
  40
  41 Note: Uses GNU getopt options parsing style
  42 EOF
  43   exit $1
  44 }
  45
  46 ##### begin command line parsing ########
  47
  48 debug=false # default
  49 temp=$(getopt -l help,d hd "$@") || usage 1
  50 eval set -- "$temp"
  51 while true; do
  52   case $1 in
  53     -d) debug=true; shift ;;
  54     -h|--help) usage ;;
  55     --) shift; break ;;
  56     *) echo "$0: Internal error! unexpected args: $*" ; exit 1 ;;
  57   esac
  58 done
  59
  60 if [[ ! $@ ]]; then
  61   echo "$0: error: expected mountpoint argument"
  62 fi
  63
  64 stale-file() {
  65   stale_dir=/nocow/btrfs-stale
  66   stale_file=$stale_dir/$vol
  67   if $stale; then
  68     mkdir -p $stale_dir
  69     printf "%s\n" $freshest_snap > $stale_file
  70   else
  71     rm -f $stale_file
  72   fi
  73
  74 }
  75 d() {
  76   if $debug; then
  77     printf "%s\n" "$*"
  78   fi
  79 }
  80
  81 for d; do
  82   vol=${d##*/}
  83   # second field, non-comment line == $d
  84   dev=$(sed -rn "s,^\s*([^#]\S*)\s+$d\s.*,\1,p" /etc/fstab /etc/mtab|head -n1)
  85
  86   d dev=$dev
  87   subvol_dir=$(sed -rn "s,^\s*[^#]\S*\s+$d\s.*\bsubvol=([a-zA-A/]+).*,\1,p" /etc/fstab /etc/mtab|head -n1)
  88   d subvol_dir=$subvol_dir
  89   # note, we need $dev because $d might not be mounted, and we do this loop
  90   # because the device in fstab for the rootfs can be different.
  91   for devx in $(btrfs fi show $dev| sed -rn 's#.*path (/\S+)$#\1#p'); do
  92     d devx=$devx
  93     root_dir=$(sed -rn "s,^\s*$devx\s+(\S+).*\bsubvolid=[05]\b.*,\1,p" /etc/mtab /etc/fstab|head -n1)
  94     if [[ $root_dir ]]; then
  95       d root_dir=$root_dir
  96       break
  97     fi
  98   done
  99   if [[ ! $root_dir ]]; then
 100     echo "$0: error could not find root subvol mount for $dev" >&2
 101     exit 1
 102   fi
 103   svp=$root_dir/$subvol_dir
 104   d "svp=$svp # subvolume path"
 105
 106   snaps=($root_dir/btrbk/$subvol_dir.20*) # Assumes we are in the 21st century.
 107   if [[ ! $snaps ]]; then
 108     # no snapshots yet
 109     echo "$0: warning: no snapshots found at $root_dir/btrbk/$subvol_dir.20*. this is expected for a brand new volume"
 110     continue
 111   fi
 112
 113   # get info on last received sub
 114   last_received=
 115   last_received_cgen=0
 116   for f in ${snaps[@]}; do
 117     show="$(btrfs sub show $f)"
 118     if echo "$show" | grep -E "Received UUID:\s+[[:alnum:]]" &>/dev/null; then
 119       d found received uuid in $f
 120       cgen=$(echo "$show" | sed -rn 's,^\s*Gen at creation:\s+([0-9]+).*,\1,p')
 121       if [[ $cgen -gt $last_received_cgen ]]; then
 122         last_received_cgen=$cgen
 123         last_received=$f
 124       fi
 125     fi
 126   done
 127   d last_received_cgen=$last_received_cgen
 128   d last_received=$last_received
 129
 130   # Get last_snap by date.
 131   # when a btrbk bugfix makes it into the distro,
 132   # we might replace this with btrbk list latest /mnt/root/$vol | ...
 133   last_snap=$(
 134     for s in ${snaps[@]}; do
 135       f=${s##*/}
 136       unix_time=$(date -d $(sed -r  's/(.{4})(..)(.{5})(..)(.*)/\1-\2-\3:\4:\5/' <<<${f#$vol.}) +%s)
 137       printf "%s %s\n" $unix_time $s
 138     done | sort -r | head -n 1 | awk '{print $2}'
 139            )
 140   if [[ ! $last_snap ]]; then
 141     # should not happen.
 142     echo "$0: error: could not find latest snapshot for $svp among ${snaps[*]}" >&2
 143     exit 1
 144   fi
 145   d last_snap=$last_snap
 146
 147   if [[ ! -e $svp ]]; then
 148     echo "$0: warning: subvol does not exist: $svp"
 149     echo "$0 assuming this host was just for receiving and latest snap is freshest"
 150     freshest_snap=$last_snap
 151     stale=true
 152     stale-file
 153     continue
 154   fi
 155
 156
 157   # if there is a last_received, we can assume stale or fresh if we are newer/older
 158   if [[ $last_received ]]; then
 159     svp_cgen=$(btrfs sub show $svp | sed -rn 's,^\s*Gen at creation:\s+([0-9]+).*,\1,p')
 160     d svp_cgen=$svp_cgen
 161     if [[ $svp_cgen -ge $last_received_cgen ]]; then
 162       stale=false
 163     else
 164       d "$svp stale: it's gen at creation, $svp_cgen, is earlier than the last received snapshot, $last_received's gen at creation: $last_received_cgen"
 165       freshest_snap=$last_received
 166       stale=true
 167     fi
 168     stale-file
 169     continue
 170   fi
 171
 172   # fallback to using last_snap as the freshest
 173   freshest_snap=$last_snap
 174   stale=true
 175   # fresh if $svp has $last_snap as a snapshot,
 176   if btrfs sub show $svp 2>/dev/null | sed '0,/^\s*Snapshot(s):/d;s/^\s*//' | \
 177       grep -xF ${last_snap#$root_dir/} ; then
 178     stale=false
 179   else # or else $svp is a snapshot of $last_snap. we use a uuid
 180     # comparison, which if I remember from the docs, is a bit more
 181     # robust, perhaps to renames.
 182     last_snap_uuid=$(btrfs sub show $last_snap| awk '$1 == "UUID:" {print $2}')
 183     if btrfs sub show $svp| grep "^\s*Parent UUID:\s*$last_snap_uuid$" &>/dev/null; then
 184       stale=false
 185     fi
 186   fi
 187
 188   stale-file
 189 done