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+$d\s.*,\1,p" /etc/fstab /etc/mtab|head -n1)
  85   d dev=$dev
  86   subvol_dir=$(sed -rn "s,^\s*[^#]\S*\s+$d\s.*\bsubvol=([a-zA-A/]+).*,\1,p" /etc/fstab /etc/mtab|head -n1)
  87   d subvol_dir=$subvol_dir
  88   # note, we need $dev because $d might not be mounted, and we do this loop
  89   # because the device in fstab for the rootfs can be different.
  90   for devx in $(btrfs fi show $dev| sed -rn 's#.*path (/\S+)$#\1#p'); do
  91     d devx=$devx
  92     root_dir=$(sed -rn "s,^\s*$devx\s+(\S+).*\bsubvolid=[05]\b.*,\1,p" /etc/mtab|head -n1)
  93     if [[ $root_dir ]]; then
  94       d root_dir=$root_dir
  95       break
  96     fi
  97   done
  98   if [[ ! $root_dir ]]; then
  99     echo "$0: error could not find root subvol mount for $dev" >&2
 100     exit 1
 101   fi
 102   svp=$root_dir/$subvol_dir
 103   d "svp=$svp # subvolume path"
 104
 105   snaps=($root_dir/btrbk/$subvol_dir.20*) # Assumes we are in the 21st century.
 106   if [[ ! $snaps ]]; then
 107     # no snapshots yet
 108     echo "$0: warning: no snapshots found at $root_dir/btrbk/$subvol_dir.20*. this is expected for a brand new volume"
 109     continue
 110   fi
 111
 112   # get info on last received sub
 113   last_received_cgen=0
 114   for f in ${snaps[@]}; do
 115     show="$(btrfs sub show $f)"
 116     if echo "$show" | grep -E "Received UUID:\s+[[:alnum:]]" &>/dev/null; then
 117       cgen=$(echo "$show" | sed -rn 's,^\s*Gen at creation:\s+([0-9]+).*,\1,p')
 118       if [[ $cgen -gt $last_received_cgen ]]; then
 119         last_received_cgen=$cgen
 120         last_received=$f
 121       fi
 122     fi
 123   done
 124   d last_received_cgen=$cgen
 125   d last_received=$f
 126
 127   # Get last_snap by date.
 128   # when a btrbk bugfix makes it into the distro,
 129   # we might replace this with btrbk list latest /mnt/root/$vol | ...
 130   last_snap=$(
 131     for s in ${snaps[@]}; do
 132       f=${s##*/}
 133       unix_time=$(date -d $(sed -r  's/(.{4})(..)(.{5})(..)(.*)/\1-\2-\3:\4:\5/' <<<${f#$vol.}) +%s)
 134       printf "%s %s\n" $unix_time $s
 135     done | sort -r | head -n 1 | awk '{print $2}'
 136            )
 137   if [[ ! $last_snap ]]; then
 138     # should not happen.
 139     echo "$0: error: could not find latest snapshot for $svp among ${snaps[*]}" >&2
 140     exit 1
 141   fi
 142
 143   if [[ ! -e $svp ]]; then
 144     echo "$0: warning: subvol does not exist: $svp"
 145     echo "$0 assuming this host was just for receiving and latest snap is freshest"
 146     freshest_snap=$last_snap
 147     stale=true
 148     stale-file
 149     continue
 150   fi
 151
 152
 153   # if there is a last_received, we can assume stale or fresh if we are newer/older
 154   if [[ $last_received ]]; then
 155     svp_cgen=$(btrfs sub show $svp | sed -rn 's,^\s*Gen at creation:\s+([0-9]+).*,\1,p')
 156     d svp_cgen=$svp_cgen
 157     if [[ $svp_cgen -ge $last_received_cgen ]]; then
 158       stale=false
 159     else
 160       echo "$svp stale: it's gen at creation, $svp_cgen, is earlier than the last received snapshot, $last_received's gen at creation: $last_received_cgen"
 161       freshest_snap=$last_received
 162       stale=true
 163     fi
 164     stale-file
 165     continue
 166   fi
 167
 168   # fallback to using last_snap as the freshest
 169   freshest_snap=$last_snap
 170   stale=true
 171   # fresh if $svp has $last_snap as a snapshot,
 172   if btrfs sub show $svp 2>/dev/null | sed '0,/^\s*Snapshot(s):/d;s/^\s*//' | \
 173       grep -xF btrbk/$last_snap &>/dev/null; then
 174     stale=false
 175   else # or else $svp is a snapshot of $last_snap. we use a uuid
 176     # comparison, which if I remember from the docs, is a bit more
 177     # robust, perhaps to renames.
 178     last_snap_uuid=$(btrfs sub show $last_snap| awk '$1 == "UUID:" {print $2}')
 179     if btrfs sub show $svp| grep "^\s*Parent UUID:\s*$last_snap_uuid$" &>/dev/null; then
 180       stale=false
 181     fi
 182   fi
 183
 184   stale-file
 185 done