--- a/usr/src/uts/common/fs/zfs/sys/dsl_dataset.h	Sun May 20 02:46:39 2012 -0500
+++ b/usr/src/uts/common/fs/zfs/sys/dsl_dataset.h	Mon May 21 12:11:39 2012 -0700
@@ -20,7 +20,7 @@
  */
 /*
  * Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
- * Copyright (c) 2011 by Delphix. All rights reserved.
+ * Copyright (c) 2012 by Delphix. All rights reserved.
  * Copyright (c) 2012, Joyent, Inc. All rights reserved.
  */
 
@@ -86,7 +86,12 @@
 	uint64_t ds_creation_time;	/* seconds since 1970 */
 	uint64_t ds_creation_txg;
 	uint64_t ds_deadlist_obj;	/* DMU_OT_DEADLIST */
-	uint64_t ds_used_bytes;
+	/*
+	 * ds_referenced_bytes, ds_compressed_bytes, and ds_uncompressed_bytes
+	 * include all blocks referenced by this dataset, including those
+	 * shared with any other datasets.
+	 */
+	uint64_t ds_referenced_bytes;
 	uint64_t ds_compressed_bytes;
 	uint64_t ds_uncompressed_bytes;
 	uint64_t ds_unique_bytes;	/* only relevant to snapshots */