--- Net2/vm/vm_object.c	2018/04/24 18:03:57	1.1
+++ 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.
@@ -454,7 +476,11 @@ vm_object_deactivate_pages(object)
 	while (!queue_end(&object->memq, (queue_entry_t) p)) {
 		next = (vm_page_t) queue_next(&p->listq);
 		vm_page_lock_queues();
-		vm_page_deactivate(p);
+		if (!p->busy)
+			vm_page_deactivate(p);	/* optimisation from mach 3.0 -
+						 * andrew@werple.apana.org.au,
+						 * Feb '93
+						 */
 		vm_page_unlock_queues();
 		p = next;
 	}
@@ -1141,12 +1167,29 @@ void vm_object_collapse(object)
 				    }
 				    else {
 					if (pp) {
+#if 1
+					    /*
+					     *  This should never happen -- the
+					     *  parent cannot have ever had an
+					     *  external memory object, and thus
+					     *  cannot have absent pages.
+					     */
+					    panic("vm_object_collapse: bad case");
+					    /* andrew@werple.apana.org.au - from
+					       mach 3.0 VM */
+#else
 					    /* may be someone waiting for it */
 					    PAGE_WAKEUP(pp);
 					    vm_page_lock_queues();
 					    vm_page_free(pp);
 					    vm_page_unlock_queues();
+#endif
 					}
+					/*
+					 *	Parent now has no page.
+					 *	Move the backing object's page
+					 *	up.
+					 */
 					vm_page_rename(p, object, new_offset);
 				    }
 				}
@@ -1161,7 +1204,21 @@ void vm_object_collapse(object)
 			 */
 
 			object->pager = backing_object->pager;
+#if 1
+			/* Mach 3.0 code */
+			/* andrew@werple.apana.org.au, 12 Feb 1993 */
+
+			/*
+			 * If there is no pager, leave paging-offset alone.
+			 */
+			if (object->pager)
+				object->paging_offset =
+					backing_object->paging_offset +
+						backing_offset;
+#else
+			/* old VM 2.5 version */
 			object->paging_offset += backing_offset;
+#endif
 
 			backing_object->pager = NULL;
 
@@ -1260,6 +1317,18 @@ void vm_object_collapse(object)
 			vm_object_reference(object->shadow = backing_object->shadow);
 			object->shadow_offset += backing_object->shadow_offset;
 
+#if 1
+			/* Mach 3.0 code */
+			/* andrew@werple.apana.org.au, 12 Feb 1993 */
+
+			/*
+			 *      Backing object might have had a copy pointer
+			 *      to us.  If it did, clear it.
+			 */
+			 if (backing_object->copy == object)
+				backing_object->copy = NULL;
+#endif
+
 			/*	Drop the reference count on backing_object.
 			 *	Since its ref_count was at least 2, it
 			 *	will not vanish; so we don't need to call