vm_object: restore handling of shadow_count for all type of objects
instead of only OBJ_ANON objects that are backing, as it is now. This is required for e.g. vm_meter is_object_active() detection, and should be useful in some more cases. Use refcount KPI for all objects, regardless of owning the object lock, and the fact that currently OBJ_ANON cannot change for the live object. Noted and reviewed by: markj Tested by: pho Sponsored by: The FreeBSD Foundation MFC after: 1 week Differential revision: https://reviews.freebsd.org/D33549
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77223d98b6
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@ -198,9 +198,9 @@ vm_object_zdtor(void *mem, int size, void *arg)
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KASSERT(object->resident_page_count == 0,
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("object %p resident_page_count = %d",
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object, object->resident_page_count));
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KASSERT(object->shadow_count == 0,
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KASSERT(atomic_load_int(&object->shadow_count) == 0,
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("object %p shadow_count = %d",
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object, object->shadow_count));
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object, atomic_load_int(&object->shadow_count)));
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KASSERT(object->type == OBJT_DEAD,
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("object %p has non-dead type %d",
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object, object->type));
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@ -222,7 +222,7 @@ vm_object_zinit(void *mem, int size, int flags)
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blockcount_init(&object->paging_in_progress);
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blockcount_init(&object->busy);
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object->resident_page_count = 0;
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object->shadow_count = 0;
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atomic_store_int(&object->shadow_count, 0);
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object->flags = OBJ_DEAD;
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mtx_lock(&vm_object_list_mtx);
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@ -574,9 +574,11 @@ vm_object_deallocate_anon(vm_object_t backing_object)
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/* Fetch the final shadow. */
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object = LIST_FIRST(&backing_object->shadow_head);
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KASSERT(object != NULL && backing_object->shadow_count == 1,
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KASSERT(object != NULL &&
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atomic_load_int(&backing_object->shadow_count) == 1,
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("vm_object_anon_deallocate: ref_count: %d, shadow_count: %d",
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backing_object->ref_count, backing_object->shadow_count));
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backing_object->ref_count,
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atomic_load_int(&backing_object->shadow_count)));
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KASSERT((object->flags & OBJ_ANON) != 0,
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("invalid shadow object %p", object));
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@ -660,7 +662,7 @@ vm_object_deallocate(vm_object_t object)
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*/
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if (!refcount_release(&object->ref_count)) {
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if (object->ref_count > 1 ||
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object->shadow_count == 0) {
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atomic_load_int(&object->shadow_count) == 0) {
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if ((object->flags & OBJ_ANON) != 0 &&
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object->ref_count == 1)
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vm_object_set_flag(object,
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@ -719,6 +721,14 @@ vm_object_destroy(vm_object_t object)
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uma_zfree(obj_zone, object);
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}
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static void
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vm_object_sub_shadow(vm_object_t object)
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{
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KASSERT(object->shadow_count >= 1,
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("object %p sub_shadow count zero", object));
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atomic_subtract_int(&object->shadow_count, 1);
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}
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static void
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vm_object_backing_remove_locked(vm_object_t object)
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{
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@ -731,9 +741,9 @@ vm_object_backing_remove_locked(vm_object_t object)
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KASSERT((object->flags & OBJ_COLLAPSING) == 0,
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("vm_object_backing_remove: Removing collapsing object."));
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vm_object_sub_shadow(backing_object);
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if ((object->flags & OBJ_SHADOWLIST) != 0) {
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LIST_REMOVE(object, shadow_list);
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backing_object->shadow_count--;
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object->flags &= ~OBJ_SHADOWLIST;
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}
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object->backing_object = NULL;
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@ -746,13 +756,15 @@ vm_object_backing_remove(vm_object_t object)
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VM_OBJECT_ASSERT_WLOCKED(object);
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backing_object = object->backing_object;
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if ((object->flags & OBJ_SHADOWLIST) != 0) {
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backing_object = object->backing_object;
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VM_OBJECT_WLOCK(backing_object);
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vm_object_backing_remove_locked(object);
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VM_OBJECT_WUNLOCK(backing_object);
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} else
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} else {
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object->backing_object = NULL;
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vm_object_sub_shadow(backing_object);
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}
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}
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static void
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@ -761,11 +773,11 @@ vm_object_backing_insert_locked(vm_object_t object, vm_object_t backing_object)
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VM_OBJECT_ASSERT_WLOCKED(object);
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atomic_add_int(&backing_object->shadow_count, 1);
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if ((backing_object->flags & OBJ_ANON) != 0) {
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VM_OBJECT_ASSERT_WLOCKED(backing_object);
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LIST_INSERT_HEAD(&backing_object->shadow_head, object,
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shadow_list);
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backing_object->shadow_count++;
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object->flags |= OBJ_SHADOWLIST;
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}
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object->backing_object = backing_object;
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@ -781,8 +793,10 @@ vm_object_backing_insert(vm_object_t object, vm_object_t backing_object)
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VM_OBJECT_WLOCK(backing_object);
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vm_object_backing_insert_locked(object, backing_object);
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VM_OBJECT_WUNLOCK(backing_object);
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} else
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} else {
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object->backing_object = backing_object;
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atomic_add_int(&backing_object->shadow_count, 1);
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}
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}
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/*
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@ -805,6 +819,7 @@ vm_object_backing_insert_ref(vm_object_t object, vm_object_t backing_object)
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VM_OBJECT_WUNLOCK(backing_object);
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} else {
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vm_object_reference(backing_object);
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atomic_add_int(&backing_object->shadow_count, 1);
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object->backing_object = backing_object;
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}
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}
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@ -831,6 +846,11 @@ vm_object_backing_transfer(vm_object_t object, vm_object_t backing_object)
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vm_object_backing_insert_locked(object, new_backing_object);
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VM_OBJECT_WUNLOCK(new_backing_object);
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} else {
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/*
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* shadow_count for new_backing_object is left
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* unchanged, its reference provided by backing_object
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* is replaced by object.
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*/
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object->backing_object = new_backing_object;
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backing_object->backing_object = NULL;
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}
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@ -1924,9 +1944,9 @@ vm_object_collapse(vm_object_t object)
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return;
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KASSERT(object->ref_count > 0 &&
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object->ref_count > object->shadow_count,
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object->ref_count > atomic_load_int(&object->shadow_count),
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("collapse with invalid ref %d or shadow %d count.",
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object->ref_count, object->shadow_count));
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object->ref_count, atomic_load_int(&object->shadow_count)));
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KASSERT((backing_object->flags &
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(OBJ_COLLAPSING | OBJ_DEAD)) == 0,
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("vm_object_collapse: Backing object already collapsing."));
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@ -1940,9 +1960,10 @@ vm_object_collapse(vm_object_t object)
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* all the resident pages in the entire backing object.
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*/
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if (backing_object->ref_count == 1) {
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KASSERT(backing_object->shadow_count == 1,
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KASSERT(atomic_load_int(&backing_object->shadow_count)
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== 1,
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("vm_object_collapse: shadow_count: %d",
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backing_object->shadow_count));
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atomic_load_int(&backing_object->shadow_count)));
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vm_object_pip_add(object, 1);
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vm_object_set_flag(object, OBJ_COLLAPSING);
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vm_object_pip_add(backing_object, 1);
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@ -2510,7 +2531,7 @@ bool
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vm_object_is_active(vm_object_t obj)
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{
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return (obj->ref_count > obj->shadow_count);
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return (obj->ref_count > atomic_load_int(&obj->shadow_count));
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}
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static int
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@ -2565,7 +2586,7 @@ vm_object_list_handler(struct sysctl_req *req, bool swap_only)
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kvo->kvo_size = ptoa(obj->size);
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kvo->kvo_resident = obj->resident_page_count;
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kvo->kvo_ref_count = obj->ref_count;
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kvo->kvo_shadow_count = obj->shadow_count;
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kvo->kvo_shadow_count = atomic_load_int(&obj->shadow_count);
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kvo->kvo_memattr = obj->memattr;
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kvo->kvo_active = 0;
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kvo->kvo_inactive = 0;
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@ -2779,7 +2800,7 @@ DB_SHOW_COMMAND(object, vm_object_print_static)
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object->resident_page_count, object->ref_count, object->flags,
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object->cred ? object->cred->cr_ruid : -1, (uintmax_t)object->charge);
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db_iprintf(" sref=%d, backing_object(%d)=(%p)+0x%jx\n",
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object->shadow_count,
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atomic_load_int(&object->shadow_count),
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object->backing_object ? object->backing_object->ref_count : 0,
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object->backing_object, (uintmax_t)object->backing_object_offset);
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