From 4630ad4d26a0b5a8774c9121b2fd42d92bb81eb0 Mon Sep 17 00:00:00 2001
From: Mathijs Kwik <mathijs@bluescreen303.nl>
Date: Mon, 13 May 2013 23:42:55 +0200
Subject: [PATCH] filesystems: add priority option for swap devices.

Useful for setting up raid0-like load balancing for swap.
By giving multiple swap devices the same prio.
---
 modules/config/swap.nix       | 11 +++++++++++
 modules/tasks/filesystems.nix |  4 +++-
 2 files changed, 14 insertions(+), 1 deletion(-)

diff --git a/modules/config/swap.nix b/modules/config/swap.nix
index a0287c948af1..7d4654ae2877 100644
--- a/modules/config/swap.nix
+++ b/modules/config/swap.nix
@@ -58,6 +58,17 @@ with utils;
             '';
           };
 
+          priority = mkOption {
+            default = null;
+            example = 2048;
+            type = types.nullOr types.int;
+            description = ''
+              Specify the priority of the swap device. Priority is a value between 0 and 32767.
+              Higher numbers indicate higher priority.
+              null lets the kernel choose a priority, which will show up as a negative value.
+            '';
+          };
+
         };
 
         config = {
diff --git a/modules/tasks/filesystems.nix b/modules/tasks/filesystems.nix
index a95bb0673a23..cc7f1f407420 100644
--- a/modules/tasks/filesystems.nix
+++ b/modules/tasks/filesystems.nix
@@ -7,6 +7,8 @@ let
 
   fileSystems = attrValues config.fileSystems;
 
+  prioOption = prio: optionalString (prio !=null) " pri=${toString prio}";
+
   fileSystemOpts = { name, ... }: {
 
     options = {
@@ -167,7 +169,7 @@ in
 
         # Swap devices.
         ${flip concatMapStrings config.swapDevices (sw:
-            "${sw.device} none swap\n"
+            "${sw.device} none swap${prioOption sw.priority}\n"
         )}
       '';