From 3439bd5ac5999ff57e0c176922251ebb4256c20e Mon Sep 17 00:00:00 2001
From: Daniel Langbein <daniel@systemli.org>
Date: Sun, 8 Oct 2023 22:02:21 +0200
Subject: [PATCH] refactor: btrfs-scrub module

---
 hosts/yodaNas/configuration.nix  |  3 +++
 hosts/yodaTab/configuration.nix  |  3 +++
 hosts/yodaTux/configuration.nix  |  3 +++
 hosts/yodaYoga/configuration.nix |  3 +++
 modules/base.nix                 | 21 ----------------
 modules/btrfs-scrub.nix          | 41 ++++++++++++++++++++++++++++++++
 6 files changed, 53 insertions(+), 21 deletions(-)
 create mode 100644 modules/btrfs-scrub.nix

diff --git a/hosts/yodaNas/configuration.nix b/hosts/yodaNas/configuration.nix
index 75385a0..05fd98f 100644
--- a/hosts/yodaNas/configuration.nix
+++ b/hosts/yodaNas/configuration.nix
@@ -59,10 +59,13 @@ in
       #../../modules/veracrypt.nix
       ../../modules/btrbk
       ../../modules/spin-down.nix
+
+      ../../modules/btrfs-scrub.nix
     ];
 
   networking.hostName = "yodaNas";
   boot.initrd.luks.devices."luks-3d974bd0-f373-469b-8e9c-2d5516e9f0f5".allowDiscards = true;
+  yoda.btrfs-scrub = ["/" "/mnt/data" "/mnt/backup"];
 
   boot.kernelParams = [];
 
diff --git a/hosts/yodaTab/configuration.nix b/hosts/yodaTab/configuration.nix
index 287d40b..289c2ff 100644
--- a/hosts/yodaTab/configuration.nix
+++ b/hosts/yodaTab/configuration.nix
@@ -58,11 +58,14 @@ in
       #../../modules/veracrypt.nix
       #../../modules/btrbk
       #../../modules/spin-down.nix
+
+      ../../modules/btrfs-scrub.nix
     ];
 
   networking.hostName = "yodaTab";
   boot.initrd.luks.devices."luks-ba8b94d0-7f70-496a-ad87-eadc5e852aad".allowDiscards = true;
   boot.initrd.luks.devices."512gb".allowDiscards = true;
+  yoda.btrfs-scrub = ["/"];
 
   boot.kernelParams = [];
 
diff --git a/hosts/yodaTux/configuration.nix b/hosts/yodaTux/configuration.nix
index f3d9cc1..c0aadf5 100644
--- a/hosts/yodaTux/configuration.nix
+++ b/hosts/yodaTux/configuration.nix
@@ -58,10 +58,13 @@ in
       #../../modules/veracrypt.nix
       #../../modules/btrbk
       #../../modules/spin-down.nix
+
+      ../../modules/btrfs-scrub.nix
     ];
 
   networking.hostName = "yodaTux";
   boot.initrd.luks.devices."luks-ea7099e3-320d-4eb3-a4c3-9910a9af817b".allowDiscards = true;
+  yoda.btrfs-scrub = ["/"];
 
   # Systemd Journal entry:
   # S Sat Sep 23 16:11:52 2023 p4 kernel: TSC found unstable after boot, most likely due to broken BIOS. Use 'tsc=unstable'.
diff --git a/hosts/yodaYoga/configuration.nix b/hosts/yodaYoga/configuration.nix
index b579a53..0854447 100644
--- a/hosts/yodaYoga/configuration.nix
+++ b/hosts/yodaYoga/configuration.nix
@@ -59,10 +59,13 @@ in
       #../../modules/veracrypt.nix
       #../../modules/btrbk
       #../../modules/spin-down.nix
+
+      ../../modules/btrfs-scrub.nix
     ];
 
   networking.hostName = "yodaYoga";
   boot.initrd.luks.devices."luks-a8521407-e25b-4f26-8e7a-a56fcbfd2e35".allowDiscards = true;
+  yoda.btrfs-scrub = ["/"];
 
   boot.kernelParams = [];
 
diff --git a/modules/base.nix b/modules/base.nix
index 11b5aac..3de06c6 100644
--- a/modules/base.nix
+++ b/modules/base.nix
@@ -98,27 +98,6 @@
     "/".options = [ "compress=zstd" "noatime" "commit=120" ];
   };
 
-  # BTRFS scrub.
-  #
-  # Scrubbing is the process of checking file consistency.
-  # Scrubbing may be done "online", meaning you don't need to unmount a subvolume to scrub it.
-  # https://nixos.wiki/wiki/Btrfs#Scrubbing
-  # Btrfs scrub is "[a]n online filesystem checking tool. Reads all the data and metadata on the filesystem and uses checksums and the duplicate copies from RAID storage to identify and repair any corrupt data."
-  # https://wiki.archlinux.org/title/btrfs#Scrub
-  # The scrub command operates on a whole filesystem, not just individual subvolumes.
-  # https://unix.stackexchange.com/a/724412
-  #
-  # As this command reads all data, it wears down the disk. One should not run it too often. For large, slow disks once per month should be fine.
-  #
-  # To run it manually:
-  #   sudo btrfs scrub start /
-  #   sudo btrfs scrub status /
-  services.btrfs.autoScrub = {
-    enable = true;
-    interval = "monthly";
-    fileSystems = [ "/" ];
-  };
-
   nix.settings.auto-optimise-store = true;
 
   # https://nixos.wiki/wiki/Storage_optimization#Automation
diff --git a/modules/btrfs-scrub.nix b/modules/btrfs-scrub.nix
new file mode 100644
index 0000000..f8313e4
--- /dev/null
+++ b/modules/btrfs-scrub.nix
@@ -0,0 +1,41 @@
+# BTRFS scrub.
+#
+# Scrubbing is the process of checking file consistency.
+# Scrubbing may be done "online", meaning you don't need to unmount a subvolume to scrub it.
+# https://nixos.wiki/wiki/Btrfs#Scrubbing
+# Btrfs scrub is "[a]n online filesystem checking tool. Reads all the data and metadata on the filesystem and uses checksums and the duplicate copies from RAID storage to identify and repair any corrupt data."
+# https://wiki.archlinux.org/title/btrfs#Scrub
+# The scrub command operates on a whole filesystem, not just individual subvolumes.
+# https://unix.stackexchange.com/a/724412
+#
+# As this command reads all data, it wears down the disk. One should not run it too often. For large, slow disks once per month should be fine.
+#
+# To run it manually:
+#   sudo btrfs scrub start /
+#   sudo btrfs scrub status /
+
+{ lib, config, options, pkgs, modulesPath, ... }:
+with lib;
+let
+  cfg = config.yoda.btrfs-scrub;
+in
+{
+  options = {
+    yoda.btrfs-scrub = mkOption {
+      type = types.listOf types.path;
+      default = ["/"];
+      example = ["/" "/mnt/data"];
+      description = ''
+        List containing each mounted BTRFS filesystem once.
+      '';
+    };
+  };
+
+  config = mkIf (length cfg > 0) {
+    services.btrfs.autoScrub = {
+      enable = true;
+      interval = "monthly";
+      fileSystems = cfg;
+    };
+  };
+}