--- a/usr/src/uts/common/fs/zfs/dmu_objset.c	Tue Nov 11 10:53:41 2008 +0100
+++ b/usr/src/uts/common/fs/zfs/dmu_objset.c	Tue Nov 11 10:05:22 2008 -0500
@@ -1213,6 +1213,38 @@
 	return (err);
 }
 
+/* ARGSUSED */
+int
+dmu_objset_prefetch(char *name, void *arg)
+{
+	objset_t *os;
+	dsl_dataset_t *ds;
+
+	os = kmem_alloc(sizeof (objset_t), KM_SLEEP);
+	if (dsl_dataset_hold(name, os, &ds)) {
+		kmem_free(os, sizeof (objset_t));
+		return (0);
+	}
+
+	if (!BP_IS_HOLE(&ds->ds_phys->ds_bp)) {
+		uint32_t aflags = ARC_NOWAIT | ARC_PREFETCH;
+		zbookmark_t zb;
+
+		zb.zb_objset = ds->ds_object;
+		zb.zb_object = 0;
+		zb.zb_level = -1;
+		zb.zb_blkid = 0;
+
+		(void) arc_read_nolock(NULL, dsl_dataset_get_spa(ds),
+		    &ds->ds_phys->ds_bp, NULL, NULL, ZIO_PRIORITY_ASYNC_READ,
+		    ZIO_FLAG_CANFAIL | ZIO_FLAG_SPECULATIVE, &aflags, &zb);
+	}
+
+	dsl_dataset_rele(ds, os);
+	kmem_free(os, sizeof (objset_t));
+	return (0);
+}
+
 void
 dmu_objset_set_user(objset_t *os, void *user_ptr)
 {