fix(apt): snapshot recursive roots separately

apt-zfs-snapshot.sh

@@ -2,13 +2,13 @@
 
 set -o pipefail
 
+set -xv
+
 declare -r config_file='/etc/apt-zfs-snapshot.conf'
 declare -r zfs_property='space.quico:auto-snapshot'
 declare -r zfs_property_value='true'
 declare -r zfs_max_name_length=255
 
-set -xv
-
 if [[ -r "${config_file}" ]]; then
     # shellcheck disable=SC1090
     source "${config_file}"
@@ -34,7 +34,7 @@ downgrade_suffix="${downgrade_suffix:-down}"
 mixed_suffix="${mixed_suffix:-mixd}"
 package_separator="${package_separator:-:}"
 
-declare -a packages operations
+declare -a packages operations successful_datasets
 declare existing_snapshots
 
 print_msg() {
@@ -78,7 +78,7 @@ parse_apt_input() {
             continue
         fi
 
-        read -r package old_version _old_arch direction new_version _new_arch _multiarch action <<<"${line}"
+        read -r package old_version _old_arch _old_multiarch direction new_version _new_arch _new_multiarch action <<<"${line}"
         [[ -n "${package}" ]] || continue
         if [[ "${action}" == '**CONFIGURE**' ]]; then
             continue
@@ -95,18 +95,31 @@ parse_apt_input() {
 }
 
 get_datasets() {
-    local dataset value
+    local dataset value candidate parent
+    local -a candidates
+    local mounted_datasets
     if [[ -n "${snapshot_roots}" ]]; then
-        read -r -a snappable_datasets <<<"${snapshot_roots}"
+        read -r -a candidates <<<"${snapshot_roots}"
+        snappable_datasets=("${candidates[@]}")
         return 0
     fi
 
+    mounted_datasets="$(findmnt -rn -t zfs -o SOURCE)"
     while IFS=$'\t' read -r dataset value; do
         [[ "${value}" == "${zfs_property_value}" && "${dataset}" != *@* ]] || continue
-        if [[ "${snap_only_local_datasets}" != 'true' ]] || findmnt -rn -t zfs -o SOURCE | grep -Fxq -- "${dataset}"; then
-            snappable_datasets+=("${dataset}")
+        if [[ "${snap_only_local_datasets}" != 'true' ]] || grep -Fxq -- "${dataset}" <<<"${mounted_datasets}"; then
+            candidates+=("${dataset}")
         fi
-    done < <(zfs get -H -o name,value "${zfs_property}")
+    done < <(zfs get -H -t filesystem,volume -o name,value "${zfs_property}")
+
+    # An inherited property marks every descendant. Keep only the highest
+    # selected dataset because the snapshot operation is recursive.
+    for dataset in "${candidates[@]}"; do
+        for parent in "${candidates[@]}"; do
+            [[ "${dataset}" == "${parent}"/* ]] && continue 2
+        done
+        snappable_datasets+=("${dataset}")
+    done
 }
 
 operation_suffix() {
@@ -181,7 +194,7 @@ prune_snapshots() {
     [[ "${dry_run}" == 'true' ]] && return 0
     limit="${snapshots_trivial_keep}"
     [[ "${severity}" == "${important_suffix}" ]] && limit="${snapshots_important_keep}"
-    for dataset in "${snappable_datasets[@]}"; do
+    for dataset in "${successful_datasets[@]}"; do
         # Query only the root dataset. Destroying its recursive snapshot also
         # removes the matching descendant snapshots as one snapshot tree.
         mapfile -t snapshots < <(zfs list -H -t snapshot -o name -s creation "${dataset}" | grep -F "${dataset}@${snapshot_prefix}${field_separator}" | grep -F "${field_separator}sev:${severity}${field_separator}")
@@ -220,10 +233,21 @@ main() {
         printf '  %s\n' "${names[@]}" >&2
         return 0
     fi
-    zfs snapshot -r "${names[@]}" || { print_msg WARN 'ZFS snapshot failed'; return 0; }
-    printf '[INFO] Created ZFS snapshots:\n' >&2
-    printf '  %s\n' "${names[@]}" >&2
-    prune_snapshots
+    successful_datasets=()
+    local name dataset snapshot_failed='false'
+    for name in "${names[@]}"; do
+        dataset="${name%%@*}"
+        if zfs snapshot -r "${name}"; then
+            successful_datasets+=("${dataset}")
+            printf '[INFO] Created ZFS snapshots for %s:\n' "${dataset}" >&2
+            printf '  %s\n' "${name}" >&2
+        else
+            snapshot_failed='true'
+            print_msg WARN "ZFS snapshot failed for ${dataset}"
+        fi
+    done
+    [[ "${snapshot_failed}" == 'false' ]] || print_msg WARN 'Snapshot set is incomplete'
+    ((${#successful_datasets[@]} > 0)) && prune_snapshots
 }
 
 main