- Update the vm_object locking in vm_map_insert().

1 files changed, 13 insertions, 8 deletions

diff --git a/sys/vm/vm_map.c b/sys/vm/vm_map.c
index 0450ee5..fdce55c 100644
--- a/sys/vm/vm_map.c
+++ b/sys/vm/vm_map.c
@@ -811,17 +811,22 @@ vm_map_insert(vm_map_t map, vm_object_t object, vm_ooffset_t offset,
 	if (cow & MAP_DISABLE_COREDUMP)
 		protoeflags |= MAP_ENTRY_NOCOREDUMP;
 
-	if (object) {
+	if (object != NULL) {
 		/*
-		 * When object is non-NULL, it could be shared with another
-		 * process.  We have to set or clear OBJ_ONEMAPPING 
-		 * appropriately.
+		 * OBJ_ONEMAPPING must be cleared unless this mapping
+		 * is trivially proven to be the only mapping for any
+		 * of the object's pages.  (Object granularity
+		 * reference counting is insufficient to recognize
+		 * aliases with precision.) 
 		 */
-		vm_object_lock(object);
-		if ((object->ref_count > 1) || (object->shadow_count != 0)) {
+		if (object != kmem_object)
+			mtx_lock(&Giant);
+		VM_OBJECT_LOCK(object);
+		if (object->ref_count > 1 || object->shadow_count != 0)
 			vm_object_clear_flag(object, OBJ_ONEMAPPING);
-		}
-		vm_object_unlock(object);
+		VM_OBJECT_UNLOCK(object);
+		if (object != kmem_object)
+			mtx_unlock(&Giant);
 	}
 	else if ((prev_entry != &map->header) &&
 		 (prev_entry->eflags == protoeflags) &&