diff --git a/health/filesystem/1.0/IFileSystem.hal b/health/filesystem/1.0/IFileSystem.hal
index 33ea3ff..a5e6487 100644
--- a/health/filesystem/1.0/IFileSystem.hal
+++ b/health/filesystem/1.0/IFileSystem.hal
@@ -16,18 +16,34 @@
 
 package android.hardware.health.filesystem@1.0;
 
+import IGarbageCollectCallback;
+
 /**
  * IFileSystem is an interface that provides operations on underlying storage
  * devices, including flash memory.
  */
 interface IFileSystem {
     /**
-     * Start garbage collection on the driver of storage devices. This function
-     * must be called at regular intervals when it is a good time for a
-     * longer-running cleanup tasks.
+     * Start garbage collection on the driver of storage devices.
      *
-     * @return result Execution result. See documentation for Result for
-     *     details.
+     * Garbage collection must be started at regular intervals when it is a good
+     * time for a longer-running cleanup tasks, roughly daily.
+     *
+     * When garbage collection finishes or encounters an error before the
+     * specified timeout, the implementation must call IGarbageCollect.finish
+     * immediately with appropriate result.
+     *
+     * If garbage collection does not finish within the specified timeout,
+     * the implementation must stop garbage collection, and must not call
+     * IGarbageCollect.finish.
+     *
+     * @param timeoutSeconds timeout in seconds. The implementation must
+     *     return after the timeout is reached.
+     *
+     * @param callback callback interface. Callback must be null if the client
+     *     does not need to receive any callbacks.
+     *
      */
-    garbageCollect() generates (Result result);
+    oneway garbageCollect(uint64_t timeoutSeconds,
+                          IGarbageCollectCallback callback);
 };