nixos: Add a filesystem module for JFS.

I'm not using JFS, but this is to mainly make jfsutils available if you
have defined a JFS filesystem in your configuration.

Signed-off-by: aszlig <aszlig@redmoonstudios.org>

nixos/modules/module-list.nix

@@ -364,6 +364,7 @@
   ./tasks/filesystems/cifs.nix
   ./tasks/filesystems/ext.nix
   ./tasks/filesystems/f2fs.nix
+  ./tasks/filesystems/jfs.nix
   ./tasks/filesystems/nfs.nix
   ./tasks/filesystems/reiserfs.nix
   ./tasks/filesystems/unionfs-fuse.nix

nixos/modules/tasks/filesystems/jfs.nix

@@ -0,0 +1,19 @@
+{ config, lib, pkgs, ... }:
+
+with lib;
+
+let
+  inInitrd = any (fs: fs == "jfs") config.boot.initrd.supportedFilesystems;
+in
+{
+  config = mkIf (any (fs: fs == "jfs") config.boot.supportedFilesystems) {
+
+    system.fsPackages = [ pkgs.jfsutils ];
+
+    boot.initrd.kernelModules = mkIf inInitrd [ "jfs" ];
+
+    boot.initrd.extraUtilsCommands = mkIf inInitrd ''
+      cp -v ${pkgs.jfsutils}/sbin/fsck.jfs "$out/bin/"
+    '';
+  };
+}