zfs: HEAVILY REFACTOR subvolume handling

lib.nix

@@ -9,28 +9,6 @@ inputs.nixpkgs.lib.extend (
     lib = prev;
   in
   {
-    serviceMountDeps =
-      serviceName: dirs:
-      { pkgs, ... }:
-      {
-        systemd.services."${serviceName}_mounts" = {
-          wants = [ "zfs.target" ];
-          before = [ "${serviceName}.service" ];
-
-          serviceConfig = {
-            Type = "oneshot";
-            RemainAfterExit = true;
-            ExecStart = "${lib.getExe pkgs.ensureZfsMounts} ${lib.strings.concatStringsSep " " dirs}";
-          };
-        };
-
-        systemd.services.${serviceName} = {
-          wants = [ "${serviceName}_mounts.service" ];
-          after = [ "${serviceName}_mounts.service" ];
-          requires = [ "${serviceName}_mounts.service" ];
-        };
-      };
-
     # stolen from: https://stackoverflow.com/a/42398526
     optimizeWithFlags =
       pkg: flags:
@@ -79,25 +57,101 @@ inputs.nixpkgs.lib.extend (
         };
       };
 
-    serviceDependZpool =
-      serviceName: zpool:
-      { config, ... }:
+    serviceMountWithZpool =
+      serviceName: zpool: dirs:
+      { pkgs, config, ... }:
       {
-        config = lib.mkIf (zpool != "") {
-          systemd.services.${serviceName} = {
-            wants = [ "zfs-import-${zpool}.service" ];
-            after = [ "zfs-import-${zpool}.service" ];
-            requires = [ "zfs-import-${zpool}.service" ];
-          };
+        systemd.services."${serviceName}-mounts" = {
+          wants = [ "zfs.target" ] ++ lib.optionals (zpool != "") [ "zfs-import-${zpool}.service" ];
+          after = lib.optionals (zpool != "") [ "zfs-import-${zpool}.service" ];
+          before = [ "${serviceName}.service" ];
 
-          # assert that the pool is even enabled
-          assertions = [
-            {
-              assertion = builtins.elem zpool config.boot.zfs.extraPools;
-              message = "${zpool} is not enabled in `boot.zfs.extraPools`";
-            }
+          serviceConfig = {
+            Type = "oneshot";
+            RemainAfterExit = true;
+            ExecStart = lib.getExe (
+              pkgs.writeShellApplication {
+                name = "ensure-zfs-mounts-with-pool-${serviceName}";
+                runtimeInputs = with pkgs; [
+                  gawk
+                  coreutils
+                  config.boot.zfs.package
+                ];
+
+                text = ''
+                  set -euo pipefail
+
+                  echo "Ensuring ZFS mounts for service: ${serviceName}"
+                  echo "Directories: ${lib.strings.concatStringsSep ", " dirs}"
+
+                  # Validate mounts exist (ensureZfsMounts already has proper PATH)
+                  ${lib.getExe pkgs.ensureZfsMounts} ${lib.strings.concatStringsSep " " dirs}
+
+                  # Additional runtime check: verify paths are on correct zpool
+                  ${lib.optionalString (zpool != "") ''
+                    echo "Verifying ZFS mountpoints are on pool '${zpool}'..."
+
+                    if ! zfs_list_output=$(zfs list -H -o name,mountpoint 2>&1); then
+                      echo "ERROR: Failed to query ZFS datasets: $zfs_list_output" >&2
+                      exit 1
+                    fi
+
+                    # This loop handles variable number of directories, shellcheck false positive
+                    # shellcheck disable=SC2043
+                    for target in ${lib.strings.concatStringsSep " " dirs}; do
+                      echo "Checking: $target"
+
+                      # Find dataset that has this mountpoint
+                      dataset=$(echo "$zfs_list_output" | awk -v target="$target" '$2 == target {print $1; exit}')
+
+                      if [ -z "$dataset" ]; then
+                        echo "ERROR: No ZFS dataset found for mountpoint: $target" >&2
+                        exit 1
+                      fi
+
+                      # Extract pool name from dataset (first part before /)
+                      actual_pool=$(echo "$dataset" | cut -d'/' -f1)
+
+                      if [ "$actual_pool" != "${zpool}" ]; then
+                        echo "ERROR: ZFS pool mismatch for $target" >&2
+                        echo " Expected pool: ${zpool}" >&2
+                        echo " Actual pool:   $actual_pool" >&2
+                        echo " Dataset:       $dataset" >&2
+                        exit 1
+                      fi
+
+                      echo "$target is on $dataset (pool: $actual_pool)"
+                    done
+
+                    echo "All paths verified successfully on pool '${zpool}'"
+                  ''}
+
+                  echo "Mount validation completed for ${serviceName}"
+                '';
+              }
+            );
+          };
+        };
+
+        systemd.services.${serviceName} = {
+          wants = [
+            "${serviceName}-mounts.service"
+          ];
+          after = [
+            "${serviceName}-mounts.service"
+          ];
+          requires = [
+            "${serviceName}-mounts.service"
           ];
         };
+
+        # assert that the pool is even enabled
+        #assertions = lib.optionals (zpool != "") [
+        #  {
+        #    assertion = builtins.elem zpool config.boot.zfs.extraPools;
+        #    message = "${zpool} is not enabled in `boot.zfs.extraPools`";
+        #  }
+        #];
       };
   }
 )