support zfs over legacy fs

default.nix

@@ -179,7 +179,7 @@ let
 
   create.zpool = q: x: ''
     zpool create ${q.name} \
-      ${lib.optionalString (!isNull x.mode || x.mode != "stripe") x.mode} \
+      ${lib.optionalString (!isNull (x.mode or null) && x.mode != "stripe") x.mode} \
       ${lib.optionalString (isAttrs x.options or null) (concatStringsSep " " (mapAttrsToList (n: v: "-o ${n}=${v}") x.options))} \
       ${lib.optionalString (isAttrs x.rootFsOptions or null) (concatStringsSep " " (mapAttrsToList (n: v: "-O ${n}=${v}") x.rootFsOptions))} \
       ''${ZFSDEVICES_${q.name}}
@@ -192,11 +192,20 @@ let
   mount.filesystem = q: x: {
     fs.${x.mountpoint} = ''
       if ! findmnt ${q.device} "/mnt${x.mountpoint}" > /dev/null 2>&1; then
-        mount ${q.device} "/mnt${x.mountpoint}" -o X-mount.mkdir
+        mount ${q.device} "/mnt${x.mountpoint}" \
+        -o X-mount.mkdir \
+        ${lib.optionalString (isList x.mountOptions or null) (concatStringsSep " " x.mountOptions)}
       fi
     '';
   };
 
+  mount.zfs_filesystem = q: x:
+    optionalAttrs ((x.options.mountpoint or "") != "none")
+      (mount.filesystem (q // { device = q.dataset; }) (x // { mountOptions = [
+        (lib.optionalString ((x.options.mountpoint or "") != "legacy") "-o zfsutil")
+        "-t zfs"
+      ]; }));
+
   mount.btrfs = mount.filesystem;
 
   mount.devices = q: x:
@@ -285,17 +294,6 @@ let
         '';
       };
 
-  mount.zfs_filesystem = q: x: {
-    zfs.${q.mountpoint} = lib.optionalString ((x.options.mountpoint or "") != "none") ''
-      if ! findmnt '${q.dataset}' /mnt${q.mountpoint} > /dev/null 2>&1; then
-        mount \
-          ${lib.optionalString ((x.options.mountpoint or "") != "legacy") "-o zfsutil"} \
-          -t zfs ${q.dataset} /mnt${q.mountpoint} \
-          -o X-mount.mkdir
-      fi
-    '';
-  };
-
   mount.zfs_volume = q: x:
     mount-f { device = "/dev/zvol/${q.dataset}"; } x.content;
 

example/zfs-over-legacy.nix

@@ -0,0 +1,42 @@
+{
+  type = "devices";
+  content = {
+    vdb = {
+      type = "table";
+      format = "gpt";
+      partitions = [
+        {
+          type = "partition";
+          # leave space for the grub aka BIOS boot
+          start = "0%";
+          end = "100%";
+          part-type = "primary";
+          bootable = true;
+          content = {
+            type = "filesystem";
+            format = "ext4";
+            mountpoint = "/";
+          };
+        }
+      ];
+    };
+    vdc = {
+      type = "zfs";
+      pool = "zroot";
+    };
+    zroot = {
+      type = "zpool";
+      mountpoint = "/";
+
+      datasets = [
+        {
+          type = "zfs_filesystem";
+          name = "zfs_fs";
+          mountpoint = "/zfs_fs";
+          options."com.sun:auto-snapshot" = "true";
+        }
+      ];
+    };
+  };
+}
+

tests/zfs-over-legacy.nix

@@ -0,0 +1,12 @@
+{ pkgs ? (import <nixpkgs> { })
+, makeDiskoTest ? (pkgs.callPackage ./lib.nix { }).makeDiskoTest
+}:
+makeDiskoTest {
+  disko-config = import ../example/zfs-over-legacy.nix;
+  extraTestScript = ''
+    machine.succeed("test -e /mnt/zfs_fs");
+    machine.succeed("mountpoint /mnt");
+    machine.succeed("mountpoint /mnt/zfs_fs");
+  '';
+}
+