Fix #331: Fix btrfs compression in example and remount subvolumes

example/btrfs-subvolumes.nix

@@ -17,14 +17,15 @@
                 type = "filesystem";
                 format = "vfat";
                 mountpoint = "/boot";
-                mountOptions = [ "umask=0077" ];
+                mountOptions = ["umask=0077"];
               };
             };
             root = {
               size = "100%";
               content = {
                 type = "btrfs";
-                extraArgs = [ "-f" ]; # Override existing partition
+                extraArgs = ["-f"]; # Override existing partition
+                mountOptions = ["compress=zstd"];
                 # Subvolumes must set a mountpoint in order to be mounted,
                 # unless their parent is mounted
                 subvolumes = {
@@ -34,21 +35,17 @@
                   };
                   # Subvolume name is the same as the mountpoint
                   "/home" = {
-                    mountOptions = [ "compress=zstd" ];
                     mountpoint = "/home";
                   };
                   # Sub(sub)volume doesn't need a mountpoint as its parent is mounted
-                  "/home/user" = { };
+                  "/home/user" = {};
                   # Parent is not mounted so the mountpoint must be set
                   "/nix" = {
-                    mountOptions = [
-                      "compress=zstd"
-                      "noatime"
-                    ];
+                    mountOptions = ["noatime"];
                     mountpoint = "/nix";
                   };
                   # This subvolume will be created but not mounted
-                  "/test" = { };
+                  "/test" = {};
                   # Subvolume for the swapfile
                   "/swap" = {
                     mountpoint = "/.swapvol";