WIP: erofs: zstd compression

FIXME: needs zstd support in the kernel, so probablt not a great idea
for now

modules/config/minimal-system.nix

@@ -5,6 +5,7 @@
     (final: prev: {
 
       composefs = final.callPackage ../../pkgs/composefs.nix { inherit prev; };
+      erofs-utils = final.callPackage ../../pkgs/erofs-utils.nix { inherit prev; };
       qemu_tiny = final.callPackage ../../pkgs/qemu.nix { inherit prev; };
       systemdUkify = final.callPackage ../../pkgs/systemd-ukify.nix { inherit prev; };
 

modules/image/disk/builder.nix

@@ -46,8 +46,10 @@ let
             split = true;
             mkfsOptions = lib.mkIf config.image.compress {
               erofs = [
-                "-zlz4hc,level=12"
-                "-Efragments,dedupe,ztailpacking"
+                "-zzstd,6" # Zstd compression
+                "-T0" # Fixed timestamp for all files
+                "-C1048576" # 1 MiB cluster size
+                "-Efragments,dedupe,ztailpacking" # Extra features
               ];
             };
             partitions = initialPartitions;

pkgs/erofs-utils.nix

@@ -0,0 +1,10 @@
+{ prev, ... }:
+
+# Build mkfs.erofs with zstd support
+prev.erofs-utils.overrideAttrs (final: p: {
+  buildInputs = p.buildInputs ++ [ prev.zstd ];
+  configureFlags = p.configureFlags ++ [
+    "--enable-multithreading"
+    "--enable-zstd"
+  ];
+})