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     # note, we need $dev because $d might not be mounted, and we do this loop
  57     # because the device in fstab for the rootfs can be different.
  58     for devx in $(btrfs fi show $dev| sed -rn 's#.*path (/\S+)$#\1#p'); do
  59         root_dir=$(sed -rn "s,^\s*$devx\s+(\S+).*\bsubvolid=0\b.*,\1,p" /etc/fstab|head -n1)
  60         if [[ $root_dir ]]; then break; fi
  61     done
  62     svp=$root_dir/$subvol_dir # subvolume path
  63
  64     snaps=($root_dir/btrbk/$subvol_dir.20*) # Assumes we are in the 21st century.
  65     if [[ ! $snaps ]]; then
  66         # no snapshots yet
  67         echo "$0: warning. no snapshots found. this is expected for a brand new volume"
  68         continue
  69     fi
  70
  71     # get info on last received sub
  72     last_received_gen=0
  73     for f in ${snaps[@]}; do
  74         show="$(btrfs sub show $f)"
  75         if echo "$show" | grep -E "Received UUID:\s+[[:alnum:]]" &>/dev/null; then
  76             cgen=$(echo "$show" | sed -rn 's,^\s*Gen at creation:\s+([0-9]+).*,\1,p')
  77             if [[ $cgen -gt $last_received_gen ]]; then
  78                 last_received_cgen=$cgen
  79                 last_received=$f
  80             fi
  81         fi
  82     done
  83
  84     # Get last_snap by date.
  85     # when a btrbk bugfix makes it into the distro,
  86     # we might replace this with btrbk list latest /mnt/root/$vol | ...
  87     last_snap=$(
  88         for s in ${snaps[@]}; do
  89             f=${s##*/}
  90             unix_time=$(date -d $(sed -r  's/(.{4})(..)(.{5})(..)(.*)/\1-\2-\3:\4:\5/' <<<${f#$vol.}) +%s)
  91             printf "%s %s\n" $unix_time $s
  92         done | sort -r | head -n 1 | awk '{print $2}'
  93              )
  94     if [[ ! $last_snap ]]; then
  95         # should not happen.
  96         echo "$0: error: could not find latest snapshot for $svp among ${snaps[*]}"
  97         ret=1
  98         continue
  99     fi
 100
 101     if [[ ! -e $svp ]]; then
 102         echo "$0: warning: subvol does not exist: $svp"
 103         echo "$0 assuming this host was just for receiving and latest snap is freshest"
 104         freshest_snap=$last_snap
 105         stale=true
 106         stale-file
 107         continue
 108     fi
 109
 110
 111     # if there is a last_received, we can assume stale or fresh if we are newer/older
 112     if [[ $last_received ]]; then
 113         svp_cgen=$(btrfs sub show $svp | sed -rn 's,^\s*Gen at creation:\s+([0-9]+).*,\1,p')
 114         if [[ $svp_cgen -ge $last_received_cgen ]]; then
 115             stale=false
 116         else
 117             echo "$svp stale: it's gen at creation, $svp_cgen, is earlier than the last received snapshot, $last_received's gen at creation: $last_received_cgen"
 118             freshest_snap=$last_received
 119             stale=true
 120         fi
 121         stale-file
 122         continue
 123     fi
 124
 125     # fallback to using last_snap as the freshest
 126     freshest_snap=$last_snap
 127     stale=true
 128     # fresh if $svp has $last_snap as a snapshot,
 129     if btrfs sub show $svp 2>/dev/null | sed '0,/^\s*Snapshot(s):/d;s/^\s*//' | \
 130             grep -xF btrbk/$last_snap &>/dev/null; then
 131         stale=false
 132     else # or else $svp is a snapshot of $last_snap. we use a uuid
 133         # comparison, which if I remember from the docs, is a bit more
 134         # robust, perhaps to renames.
 135         last_snap_uuid=$(btrfs sub show $last_snap| awk '$1 == "UUID:" {print $2}')
 136         if btrfs sub show $svp| grep "^\s*Parent UUID:\s*$last_snap_uuid$" &>/dev/null; then
 137             stale=false
 138         fi
 139     fi
 140
 141     stale-file
 142
 143 done
 144 exit $ret