use time embedded in filename instead of stat

verify the head snapshot is a read-only snapshot early

1 files changed, 24 insertions, 10 deletions

diff --git a/push-btrfs b/push-btrfs
index 5e9b537..3284b69 100755
--- a/push-btrfs
+++ b/push-btrfs
@@ -1,5 +1,5 @@
 #!/bin/bash
-MAX_AGE_SECONDS=60
+MIN_AGE_SECONDS=60
 CONFIG_DIR=/etc/btrfs-backup/remotes
 
 die()
@@ -15,7 +15,7 @@ read_config()
 
 check_dependencies()
 {
-        for c in flock jq btrfs pv realpath stat date mv ln rm
+        for c in flock jq btrfs pv realpath stat egrep date mv ln rm
         do
                 command -v $c >/dev/null
         done
@@ -31,10 +31,15 @@ is_subvolume()
         btrfs subvolume show -- "$1" >/dev/null 2>&1
 }
 
+is_readonly_subvolume()
+{
+        btrfs subvolume show -- "$1" | egrep -q '^      Flags:.*\breadonly\b'
+}
+
 get_age()
 {
         now=$(date +%s)
-        then=$(stat -L -c %Y "$1")
+        then=$(date +%s -d "${1##*.snapshot~}")
         echo $((now - then))
 }
 
@@ -80,16 +85,25 @@ esac
 
 is_subvolume "$src"
 
-if [ "$(get_age "$remote_head")" -le "$MAX_AGE_SECONDS" ]
+if [ "$remote_head" ]
 then
-        echo "Up-to-date." >&2
-        exit
-else
-        new_snapshot=${src%/}/.snapshot~$(date -Ins)
-        btrfs subvolume snapshot -r -- "$src" "$new_snapshot"
+        is_readonly_subvolume "$remote_head"
+
+        AGE=$(get_age "$remote_head")
+        if [ "$AGE" -le "$MIN_AGE_SECONDS" ]
+        then
+                echo "Up-to-date." >&2
+                exit
+        fi
 fi
 
-btrfs send ${remote_head:+ -p "$remote_head"} -- "$new_snapshot" | pv | btrfs_receive "$dst"
+new_snapshot=${src%/}/.snapshot~$(date -Ins)
+btrfs subvolume snapshot -r -- "$src" "$new_snapshot"
+if ! btrfs send ${remote_head:+ -p "$remote_head"} -- "$new_snapshot" | pv | btrfs_receive "$dst"
+then
+        btrfs subvolume delete "$new_snapshot"
+        exit 1
+fi
 jq --arg h "$new_snapshot" '. | .head=$h' <"$config_file" >"$config_file_temp"
 mv -T -- "$config_file_temp" "$config_file"