From 00076c7b818087a29b3f629c73542ebf3b98feec Mon Sep 17 00:00:00 2001
From: Daniel Barlow <dan@telent.net>
Date: Wed, 17 Apr 2024 12:59:13 +0100
Subject: [PATCH] mount service: use uevent-watch

---
 examples/arhcive.nix          |  2 +-
 modules/mount/default.nix     | 50 ++++++++++++++++++++---------------
 modules/mount/service.nix     | 13 +++------
 tests/inout/configuration.nix | 21 ++++-----------
 4 files changed, 39 insertions(+), 47 deletions(-)

diff --git a/examples/arhcive.nix b/examples/arhcive.nix
index 7d30d91..6616d81 100644
--- a/examples/arhcive.nix
+++ b/examples/arhcive.nix
@@ -83,7 +83,7 @@ in rec {
   };
 
   services.mount_external_disk = svc.mount.build {
-    device = "LABEL=backup-disk";
+    partlabel = "backup-disk";
     mountpoint = "/srv";
     fstype = "ext4";
   };
diff --git a/modules/mount/default.nix b/modules/mount/default.nix
index 310f892..76e1cf5 100644
--- a/modules/mount/default.nix
+++ b/modules/mount/default.nix
@@ -19,28 +19,36 @@ in {
       type = liminix.lib.types.serviceDefn;
     };
   };
-  config.system.service = {
-    mount = liminix.callService ./service.nix {
-      device = mkOption {
-        type = types.str;
-        example = "/dev/sda1";
-      };
-      mountpoint = mkOption {
-        type = types.str;
-        example = "/mnt/media";
-      };
-      options = mkOption {
-        type = types.listOf types.str;
-        default = [];
-        example = ["noatime" "ro" "sync"];
-      };
-      fstype = mkOption {
-        type = types.str;
-        default = "auto";
-        example = "vfat";
-      };
+  imports = [ ../mdevd.nix ];
+  config.system.service.mount =
+    let svc = liminix.callService ./service.nix {
+          partlabel = mkOption {
+            type = types.str;
+            example = "my-usb-stick";
+          };
+          mountpoint = mkOption {
+            type = types.str;
+            example = "/mnt/media";
+          };
+          options = mkOption {
+            type = types.listOf types.str;
+            default = [];
+            example = ["noatime" "ro" "sync"];
+          };
+          fstype = mkOption {
+            type = types.str;
+            default = "auto";
+            example = "vfat";
+          };
+        };
+    in svc // {
+      build = args:
+        let args' = args // {
+              dependencies = (args.dependencies or []) ++ [config.services.mdevd];
+            };
+        in svc.build args' ;
     };
-  };
+
   config.programs.busybox  = {
     applets = ["blkid" "findfs"];
     options = {
diff --git a/modules/mount/service.nix b/modules/mount/service.nix
index 7491bff..ed30879 100644
--- a/modules/mount/service.nix
+++ b/modules/mount/service.nix
@@ -1,10 +1,12 @@
 {
   liminix
+, uevent-watch
 , lib
 }:
-{ device, mountpoint, options, fstype }:
+{ partlabel, mountpoint, options, fstype }:
 let
   inherit (liminix.services) longrun oneshot;
+  device = "/dev/disk/by-partlabel/${partlabel}";
   options_string =
     if options == [] then "" else "-o ${lib.concatStringsSep "," options}";
   mount_service = oneshot {
@@ -18,14 +20,7 @@ in longrun {
   isTrigger = true;
   buildInputs = [ mount_service ];
 
-  # This accommodates bringing the service up when the device appears.
-  # It doesn't bring it down on unplug because unmount will probably
-  # fail anyway (so don't do that)
   run = ''
-    while ! findfs ${device}; do
-      echo waiting for device ${device}
-      sleep 1
-    done
-    s6-rc -b -u change ${mount_service.name}
+    ${uevent-watch}/bin/uevent-watch -s ${mount_service.name} -n ${device} partname=${partlabel} devtype=partition
   '';
 }
diff --git a/tests/inout/configuration.nix b/tests/inout/configuration.nix
index cf474a6..6a326da 100644
--- a/tests/inout/configuration.nix
+++ b/tests/inout/configuration.nix
@@ -47,20 +47,9 @@ in rec {
   rootfsType = "jffs2";
   hostname = "inout";
 
-  services.watch_mount_srv =
-    let
-      node = "/dev/disk/by-partlabel/backup-disk";
-      mount = oneshot {
-        name = "mount-srv";
-        up = "mount -t ext2 ${node} /srv";
-        down = "umount /srv";
-      };
-    in longrun {
-      name = "mount_srv";
-      run = ''
-        ${pkgs.uevent-watch}/bin/uevent-watch -s ${mount.name} -n ${node} partname=backup-disk devtype=partition
-      '';
-      dependencies = [ config.services.mdevd ];
-      buildInputs = [ mount ];
-    };
+  services.mount_backup_disk = svc.mount.build {
+    partlabel = "backup-disk";
+    mountpoint = "/srv";
+    fstype = "ext4";
+  };
 }