Add support for partitioning btrfs volumes

lib/modules/fileSystems.nix

@@ -105,6 +105,7 @@ in
               ''
             ])}
             ${cfg.diskSetup.scripts.partition}
+            ${cfg.btrfs.script}
             ${mountScript}
             ${cfg.diskSetup.scripts.swap}
           '';

lib/modules/fileSystems/btrfs.nix

@@ -0,0 +1,108 @@
+{ lib, config, ... }:
+let
+  inherit (lib) types mkOption;
+  cfg = config.valhalla.fileSystems.btrfs;
+
+  profileType = types.enum [
+    "raid0"
+    "raid1"
+    "raid1c3"
+    "raid1c4"
+    "raid5"
+    "raid6"
+    "raid10"
+    "dup"
+    "single"
+  ];
+
+  volumeType = types.submodule (
+    { config, name, ... }: {
+      options = {
+        mountPoint = mkOption {
+          type = types.nullOr types.str;
+          description = "The path to mount the volume to.";
+          default = null;
+        };
+
+        devices = mkOption {
+          type = types.listOf types.str;
+          description = "The devices of the btrfs volume.";
+        };
+
+        label = mkOption {
+          type = types.nullOr types.str;
+          description = "The label of the volume.";
+          default = name;
+        };
+
+        dataProfile = mkOption {
+          type = types.nullOr profileType;
+          description = "The data profile.";
+          default = null;
+        };
+
+        metadataProfile = mkOption {
+          type = types.nullOr profileType;
+          description = "The metadata profile.";
+          default = null;
+        };
+      };
+    }
+  );
+in
+{
+  options = {
+    valhalla = {
+      fileSystems.btrfs = {
+        volumes = mkOption {
+          type = types.attrsOf volumeType;
+          description = "The btrfs volumes of the system.";
+          default = { };
+        };
+
+        script = mkOption {
+          type = types.str;
+          description = "The script for creating the btrfs volumes.";
+          default = lib.strings.concatLines (
+            builtins.map
+              (
+                _: builtins.concatStringsSep " " (
+                  [ "mkfs.btrfs" ] ++
+                  (lib.optionals (_.metadataProfile != null) [ "--metadata" "${_.metadataProfile}" ]) ++
+                  (lib.optionals (_.dataProfile != null) [ "--data" "${_.dataProfile}" ]) ++
+                  (lib.optionals (_.label != null) [ "--label" "${_.label}" ]) ++
+                  _.devices
+                )
+              )
+              (builtins.attrValues cfg.volumes)
+          );
+        };
+      };
+    };
+  };
+
+  config = {
+    valhalla = {
+      linux.programs.btrfs = lib.optionalAttrs
+        (builtins.any
+          (_: (builtins.length _.devices) > 1)
+          (builtins.attrValues cfg.volumes))
+        {
+          enable = true;
+          pools = true;
+        };
+
+      fileSystems.mounts = lib.attrsets.concatMapAttrs
+        (
+          name: volume:
+            if (volume.mountPoint != null) then {
+              ${volume.mountPoint} = {
+                device = builtins.elemAt volume.devices 0;
+                fsType = "btrfs";
+              };
+            } else { }
+        )
+        cfg.volumes;
+    };
+  };
+}

profiles/machines/manuel/server.nix

@@ -5,8 +5,11 @@ in {
 
   config = {
     valhalla = {
-      fileSystems.diskSetup.devices = {
+      fileSystems = {
+        diskSetup.devices = {
           OS = {
+            path = "/dev/sda";
+
             partitions = {
               Boot = {
                 index = 1;
@@ -25,8 +28,16 @@ in {
                 index = 3;
                 label = lib.mkDefault config.valhalla.boot.label;
                 type = "linux";
-              format = fs.ext4;
+              };
+            };
+          };
+        };
+
+        btrfs = {
+          volumes = {
+            OS = {
               mountPoint = "/";
+              devices = [ "/dev/sda3" "/dev/sdb" ];
             };
           };
         };