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 # usage: $0 SUBVOL_MOUNTPOINT...
  17 #
  18 # In git, this is not not executable because it's meant to be installed
  19 # using ./install-my-scripts
  20 #
  21 # If latest subvols $@ are not mounted, exit 1, print message, and touch
  22 # /nocow/btrfs-stale/$subvol
  23 #
  24 # Either SUBVOL_MOUNTPOINT is a snapshot of the latest, or
  25 # the latest snapshot is snapshot of SUBVOL_MOUNTPOINT.
  26
  27 [[ $EUID == 0 ]] || exec sudo -E "$BASH_SOURCE" "$@"
  28
  29 set -eE -o pipefail
  30 trap 'echo "$0:$LINENO:error: \"$BASH_COMMAND\" returned $?" >&2' ERR
  31
  32 shopt -s nullglob
  33
  34 if [[ ! $@ ]]; then
  35     echo "$0: error: expected mountpoint argument"
  36 fi
  37
  38 stale-file() {
  39     stale_dir=/nocow/btrfs-stale
  40     stale_file=$stale_dir/$vol
  41     if $stale; then
  42         mkdir -p $stale_dir
  43         printf "%s\n" $freshest_snap > $stale_file
  44         ret=1
  45     else
  46         rm -f $stale_file
  47     fi
  48
  49 }
  50
  51 ret=0
  52 for d; do
  53     vol=${d##*/}
  54     dev=$(sed -rn "s,^\s*([^#]\S*)\s+$d\s.*,\1,p" /etc/fstab|head -n1)
  55     subvol_dir=$(sed -rn "s,^\s*[^#]\S*\s+$d\s.*\bsubvol=([a-zA-A/]+).*,\1,p" /etc/fstab|head -n1)
  56     root_dir=$(sed -rn "s,^\s*$dev\s+(\S+).*\bsubvolid=0\b.*,\1,p" /etc/fstab|head -n1)
  57     svp=$root_dir/$subvol_dir # subvolume path
  58
  59
  60
  61     snaps=($root_dir/btrbk/$subvol_dir.20*) # Assumes we are in the 21st century.
  62     if [[ ! $snaps ]]; then
  63         # no snapshots yet
  64         echo "$0: warning. no snapshots found. this is expected for a brand new volume"
  65         continue
  66     fi
  67
  68     # get info on last received sub
  69     last_received_gen=0
  70     for f in ${snaps[@]}; do
  71         show="$(btrfs sub show $f)"
  72         if echo "$show" | grep -E "Received UUID:\s+[[:alnum:]]" &>/dev/null; then
  73             cgen=$(echo "$show" | sed -rn 's,^\s*Gen at creation:\s+([0-9]+).*,\1,p')
  74             if [[ $cgen -gt $last_received_gen ]]; then
  75                 last_received_cgen=$cgen
  76                 last_received=$f
  77             fi
  78         fi
  79     done
  80
  81     # Get last_snap by date.
  82     # when a btrbk bugfix makes it into the distro,
  83     # we might replace this with btrbk list latest /mnt/root/$vol | ...
  84     last_snap=$(
  85         for s in ${snaps[@]}; do
  86             f=${s##*/}
  87             printf "%s %s\n" $(date -d $(sed -r  's/(.{4})(..)(.{5})(..)(.*)/\1-\2-\3:\4:\5/' <<<${f#$vol.}) +%s) $f
  88         done | sort -r | head -n 1 | awk '{print $2}'
  89              )
  90     if [[ ! $last_snap ]]; then
  91         # should not happen.
  92         echo "$0: error: could not find latest snapshot for $svp among ${snaps[*]}"
  93         ret=1
  94         continue
  95     fi
  96
  97     if [[ ! -e $svp ]]; then
  98         echo "$0: warning: subvol we want to check does not exist: $svp"
  99         stale-file=$last_snap
 100         stale-file
 101         continue
 102     fi
 103
 104
 105     # if there is a last_received, we can assume stale or fresh if we are newer/older
 106     if [[ $last_received ]]; then
 107         svp_cgen=$(btrfs sub show $svp | sed -rn 's,^\s*Gen at creation:\s+([0-9]+).*,\1,p')
 108         if [[ $svp_cgen -ge $last_received_cgen ]]; then
 109             stale=false
 110         else
 111             echo "$svp stale: it's gen at creation, $svp_cgen, is earlier than the last received snapshot, $last_received's gen at creation: $last_received_cgen"
 112             freshest_snap=$last_received
 113             stale=true
 114         fi
 115         stale-file
 116         continue
 117     fi
 118
 119     freshest_snap=$last_snap
 120     stale=true
 121     # fresh if $svp has $last_snap as a snapshot,
 122     if btrfs sub show $svp 2>/dev/null | sed '0,/^\s*Snapshot(s):/d;s/^\s*//' | \
 123             grep -xF btrbk/$last_snap &>/dev/null; then
 124         stale=false
 125     else # or else $svp is a snapshot of $last_snap. we use a uuid
 126         # comparison, which if I remember from the docs, is a bit more
 127         # robust, perhaps to renames.
 128         last_snap_uuid=$(btrfs sub show $last_snap| awk '$1 == "UUID:" {print $2}')
 129         if btrfs sub show $svp| grep "^\s*Parent UUID:\s*$last_snap_uuid$" &>/dev/null; then
 130             stale=false
 131         fi
 132     fi
 133
 134     stale-file
 135
 136 done
 137 exit $ret