nixosTests: test spaces in mount options via btrfs subvols

Also enabled the btrfs tests for installer-systemd-stage-1 again

nixos/release-combined.nix

@@ -76,6 +76,7 @@ in rec {
         (onFullSupported "nixos.tests.i3wm")
         (onSystems ["x86_64-linux"] "nixos.tests.installer.btrfsSimple")
         (onSystems ["x86_64-linux"] "nixos.tests.installer.btrfsSubvolDefault")
+        (onSystems ["x86_64-linux"] "nixos.tests.installer.btrfsSubvolEscape")
         (onSystems ["x86_64-linux"] "nixos.tests.installer.btrfsSubvols")
         (onSystems ["x86_64-linux"] "nixos.tests.installer.luksroot")
         (onSystems ["x86_64-linux"] "nixos.tests.installer.lvm")

nixos/tests/installer-systemd-stage-1.nix

@@ -8,9 +8,10 @@
   # them when fixed.
   inherit (import ./installer.nix { inherit system config pkgs; systemdStage1 = true; })
     # bcache
-    # btrfsSimple
-    # btrfsSubvolDefault
-    # btrfsSubvols
+    btrfsSimple
+    btrfsSubvolDefault
+    btrfsSubvolEscape
+    btrfsSubvols
     # encryptedFSWithKeyfile
     # grub1
     # luksroot

nixos/tests/installer.nix

@@ -911,4 +911,25 @@ in {
       )
     '';
   };
+
+  # Test to see if we can deal with subvols that need to be escaped in fstab
+  btrfsSubvolEscape = makeInstallerTest "btrfsSubvolEscape" {
+    createPartitions = ''
+      machine.succeed(
+          "sgdisk -Z /dev/vda",
+          "sgdisk -n 1:0:+1M -n 2:0:+1G -N 3 -t 1:ef02 -t 2:8200 -t 3:8300 -c 3:root /dev/vda",
+          "mkswap /dev/vda2 -L swap",
+          "swapon -L swap",
+          "mkfs.btrfs -L root /dev/vda3",
+          "btrfs device scan",
+          "mount LABEL=root /mnt",
+          "btrfs subvol create '/mnt/nixos in space'",
+          "btrfs subvol create /mnt/boot",
+          "umount /mnt",
+          "mount -o 'defaults,subvol=nixos in space' LABEL=root /mnt",
+          "mkdir /mnt/boot",
+          "mount -o defaults,subvol=boot LABEL=root /mnt/boot",
+      )
+    '';
+  };
 }