Pull down the device during shutdown if writeback device is configured

Author: keszybz

src/generator.rs

@@ -217,6 +217,16 @@ fn handle_zram_swap(output_directory: &Path, device: &Device) -> Result<()> {
 
     handle_zram_bindings(output_directory, device, "dev-%i.swap")?;
 
+    let shutdown_conflicts = if device.writeback_dev.is_some() {
+        // We need to shut down the zram device to disconnect the writeback device.
+        // Once https://github.com/systemd/systemd/issues/35303 is resolved, we
+        // may revisit this and rely on the systemd to pull down the device stack
+        // if appropriate.
+        "Conflicts=shutdown.target\n"
+    } else {
+        ""
+    };
+
     /* dev-zramX.swap */
     write_contents(
         output_directory,
@@ -232,7 +242,7 @@ DefaultDependencies=no
 Requires=systemd-zram-setup@{zram_device}.service
 After=systemd-zram-setup@{zram_device}.service
 Before=swap.target
-
+{shutdown_conflicts}
 [Swap]
 What=/dev/{zram_device}
 Priority={swap_priority}
@@ -241,6 +251,7 @@ Options={options}
             zram_device = device.name,
             swap_priority = device.swap_priority,
             options = device.options.replace('%', "%%"),
+            shutdown_conflicts = shutdown_conflicts,
         ),
     )?;
 

tests/10-example/run.expected/units/dev-zram0.swap

@@ -9,6 +9,7 @@ DefaultDependencies=no
 [email protected]
 [email protected]
 Before=swap.target
+Conflicts=shutdown.target
 
 [Swap]
 What=/dev/zram0