Panic if object is deallocated too many times.

Slight change to reverse collapsing so that vm_object_deallocate doesn't
have to be called recursively.
Removed half of a previous fix - the renamed page during a collapse doesn't
need to be marked dirty because the pager backing store pointers are copied
- thus preserving the page's data. This assumes that pages without backing
store are always dirty (except perhaps for when they are first zeroed, but
this doesn't matter).
Switch order of two lines of code so that the correct pager is removed
from the hash list. The previous code bogusly passed a NULL pointer to
vm_object_remove(). The call to vm_object_remove() should be unnecessary
if named anonymous objects were being dealt with correctly. They are
currently marked as OBJ_INTERNAL, which really screws up things (such as
this).

1 files changed, 7 insertions, 5 deletions

diff --git a/sys/vm/vm_object.c b/sys/vm/vm_object.c
index 6db081a..29162f8 100644
--- a/sys/vm/vm_object.c
+++ b/sys/vm/vm_object.c
@@ -61,7 +61,7 @@
  * any improvements or extensions that they make and grant Carnegie the
  * rights to redistribute these changes.
  *
- * $Id: vm_object.c,v 1.22 1995/02/12 09:19:44 davidg Exp $
+ * $Id: vm_object.c,v 1.23 1995/02/18 06:48:33 davidg Exp $
  */
 
 /*
@@ -245,6 +245,9 @@ vm_object_deallocate(object)
 
 	while (object != NULL) {
 
+		if (object->ref_count == 0)
+			panic("vm_object_deallocate: object deallocated too many times");
+
 		/*
 		 * The cache holds a reference (uncounted) to the object; we
 		 * must lock it before removing the object.
@@ -284,8 +287,8 @@ vm_object_deallocate(object)
 						vm_object_unlock(object);
 						vm_object_cache_unlock();
 						robject->ref_count += 1;
-						vm_object_deallocate(robject);
-						return;
+						object = robject;
+						continue;
 					}
 					vm_object_cache_unlock();
 					vm_object_unlock(object);
@@ -1377,7 +1380,6 @@ vm_object_collapse(object)
 						vm_page_unlock_queues();
 					} else {
 						vm_page_rename(p, object, new_offset);
-						p->dirty = VM_PAGE_BITS_ALL;
 					}
 				}
 			}
@@ -1398,8 +1400,8 @@ vm_object_collapse(object)
 					 * shadow object.
 					 */
 					bopager = backing_object->pager;
-					backing_object->pager = NULL;
 					vm_object_remove(backing_object->pager);
+					backing_object->pager = NULL;
 					swap_pager_copy(
 					    bopager, backing_object->paging_offset,
 					    object->pager, object->paging_offset,