From 722dde361ca51864fd9b3b6b9a78875e436fbc24 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?J=C3=B6rg=20Thalheim?= <joerg@thalheim.io>
Date: Fri, 26 Aug 2022 10:28:07 +0200
Subject: zfs: support for root dataset mountpoint and mountpoint=none

---
 default.nix     | 35 +++++++++++++++++++++++++++--------
 example/zfs.nix |  7 +++++++
 tests/zfs.nix   |  4 ++--
 3 files changed, 36 insertions(+), 10 deletions(-)

diff --git a/default.nix b/default.nix
index ac84345..1865d69 100644
--- a/default.nix
+++ b/default.nix
@@ -256,29 +256,48 @@ let
 
   mount.zfs = mount.noop;
 
-  mount.zpool = q: x: (
+  mount.zpool = q: x:
+    let
+      datasets = [{
+        inherit (q) name;
+        type = "zfs_filesystem";
+        dataset = q.name;
+        mountpoint = x.mountpoint or "/${q.name}";
+        options = q.rootFsOptions or { };
+      }] ++ x.datasets;
+    in
     recursiveUpdate
-      (foldl' recursiveUpdate { } (map (mount-f (q // { pool = q.name; })) x.datasets))
+      (foldl' recursiveUpdate { }
+        (
+          (map
+            (x: mount-f
+              ({
+                dataset = x.dataset or "${q.name}/${x.name}";
+                mountpoint = x.mountpoint or "/${q.name}/${x.name}";
+              } // q)
+              x)
+            datasets)
+        )
+      )
       {
         zpool.${q.device} = ''
           zpool list '${q.name}' >/dev/null 2>/dev/null || zpool import '${q.name}'
         '';
-      }
-  );
+      };
 
   mount.zfs_filesystem = q: x: {
-    zfs.${x.mountpoint} = ''
-      if ! findmnt '${q.pool}/${x.name}' /mnt${x.mountpoint} > /dev/null 2>&1; then
+    zfs.${q.mountpoint} = lib.optionalString ((x.options.mountpoint or "") != "none") ''
+      if ! findmnt '${q.dataset}' /mnt${q.mountpoint} > /dev/null 2>&1; then
         mount \
           ${lib.optionalString ((x.options.mountpoint or "") != "legacy") "-o zfsutil"} \
-          -t zfs ${q.pool}/${x.name} /mnt${x.mountpoint} \
+          -t zfs ${q.dataset} /mnt${q.mountpoint} \
           -o X-mount.mkdir
       fi
     '';
   };
 
   mount.zfs_volume = q: x:
-    mount-f { device = "/dev/zvol/${q.pool}/${x.name}"; } x.content;
+    mount-f { device = "/dev/zvol/${q.dataset}"; } x.content;
 
 in
 {
diff --git a/example/zfs.nix b/example/zfs.nix
index 2b56bd7..60e4700 100644
--- a/example/zfs.nix
+++ b/example/zfs.nix
@@ -16,6 +16,8 @@
         compression = "lz4";
         "com.sun:auto-snapshot" = "false";
       };
+      mountpoint = "/";
+
       datasets = [
         {
           type = "zfs_filesystem";
@@ -23,6 +25,11 @@
           mountpoint = "/zfs_fs";
           options."com.sun:auto-snapshot" = "true";
         }
+        {
+          type = "zfs_filesystem";
+          name = "zfs_unmounted_fs";
+          options.mountpoint = "none";
+        }
         {
           type = "zfs_filesystem";
           name = "zfs_legacy_fs";
diff --git a/tests/zfs.nix b/tests/zfs.nix
index ebc6b04..5940c4d 100644
--- a/tests/zfs.nix
+++ b/tests/zfs.nix
@@ -17,9 +17,9 @@ makeDiskoTest {
     assert_property("zroot", "com.sun:auto-snapshot", "false")
     assert_property("zroot/zfs_fs", "com.sun:auto-snapshot", "true")
     assert_property("zroot/zfs_testvolume", "volsize", "10M")
+    assert_property("zroot/zfs_unmounted_fs", "mountpoint", "none")
 
-    # FIXME: we cannot mount rootfs yet
-    #machine.succeed("mountpoint /mnt");
+    machine.succeed("mountpoint /mnt");
     machine.succeed("mountpoint /mnt/zfs_fs");
     machine.succeed("mountpoint /mnt/zfs_legacy_fs");
     machine.succeed("mountpoint /mnt/ext4onzfs");
-- 
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