--- Net2/vm/vm_object.c	2018/04/24 18:09:22	1.1.1.2
+++ Net2/vm/vm_object.c	2018/04/24 18:14:58	1.1.1.3
@@ -33,7 +33,8 @@
  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  * SUCH DAMAGE.
  *
- *	@(#)vm_object.c	7.4 (Berkeley) 5/7/91
+ *	from: @(#)vm_object.c	7.4 (Berkeley) 5/7/91
+ *	vm_object.c,v 1.4 1993/06/30 03:48:26 andrew Exp
  *
  *
  * Copyright (c) 1987, 1990 Carnegie-Mellon University.
@@ -248,6 +249,26 @@ void vm_object_deallocate(object)
 		 */
 
 		if (object->can_persist) {
+			register vm_page_t	p;
+
+			/*
+			 * Check for dirty pages in object
+			 * Print warning as this may signify kernel bugs
+			 * pk@cs.few.eur.nl	- 4/15/93
+			 */
+			p = (vm_page_t) queue_first(&object->memq);
+			while (!queue_end(&object->memq, (queue_entry_t) p)) {
+				VM_PAGE_CHECK(p);
+
+				if (pmap_is_modified(VM_PAGE_TO_PHYS(p)) ||
+								!p->clean) {
+
+					printf("vm_object_dealloc: persistent object %x isn't clean\n", object);
+					goto cant_persist;
+				}
+
+				p = (vm_page_t) queue_next(&p->listq);
+			}
 
 			queue_enter(&vm_object_cached_list, object,
 				vm_object_t, cached_list);
@@ -260,6 +281,7 @@ void vm_object_deallocate(object)
 			vm_object_cache_trim();
 			return;
 		}
+	cant_persist:;
 
 		/*
 		 *	Make sure no one can look us up now.