git: 4cf9f5d807a7 - main - vm_object: restore handling of shadow_count for all type of objects
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Date: Wed, 02 Feb 2022 10:39:34 UTC
The branch main has been updated by kib:
URL: https://cgit.FreeBSD.org/src/commit/?id=4cf9f5d807a7767a2ec6113c99bbba024d08b489
commit 4cf9f5d807a7767a2ec6113c99bbba024d08b489
Author: Konstantin Belousov <kib@FreeBSD.org>
AuthorDate: 2021-12-17 20:55:45 +0000
Commit: Konstantin Belousov <kib@FreeBSD.org>
CommitDate: 2022-02-02 09:39:51 +0000
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
---
sys/vm/vm_object.c | 57 +++++++++++++++++++++++++++++++++++++-----------------
1 file changed, 39 insertions(+), 18 deletions(-)
diff --git a/sys/vm/vm_object.c b/sys/vm/vm_object.c
index 7bc503f7afdf..94f9bed3d9b8 100644
--- a/sys/vm/vm_object.c
+++ b/sys/vm/vm_object.c
@@ -198,9 +198,9 @@ vm_object_zdtor(void *mem, int size, void *arg)
KASSERT(object->resident_page_count == 0,
("object %p resident_page_count = %d",
object, object->resident_page_count));
- KASSERT(object->shadow_count == 0,
+ KASSERT(atomic_load_int(&object->shadow_count) == 0,
("object %p shadow_count = %d",
- object, object->shadow_count));
+ object, atomic_load_int(&object->shadow_count)));
KASSERT(object->type == OBJT_DEAD,
("object %p has non-dead type %d",
object, object->type));
@@ -222,7 +222,7 @@ vm_object_zinit(void *mem, int size, int flags)
blockcount_init(&object->paging_in_progress);
blockcount_init(&object->busy);
object->resident_page_count = 0;
- object->shadow_count = 0;
+ atomic_store_int(&object->shadow_count, 0);
object->flags = OBJ_DEAD;
mtx_lock(&vm_object_list_mtx);
@@ -574,9 +574,11 @@ vm_object_deallocate_anon(vm_object_t backing_object)
/* Fetch the final shadow. */
object = LIST_FIRST(&backing_object->shadow_head);
- KASSERT(object != NULL && backing_object->shadow_count == 1,
+ KASSERT(object != NULL &&
+ atomic_load_int(&backing_object->shadow_count) == 1,
("vm_object_anon_deallocate: ref_count: %d, shadow_count: %d",
- backing_object->ref_count, backing_object->shadow_count));
+ backing_object->ref_count,
+ atomic_load_int(&backing_object->shadow_count)));
KASSERT((object->flags & OBJ_ANON) != 0,
("invalid shadow object %p", object));
@@ -660,7 +662,7 @@ vm_object_deallocate(vm_object_t object)
*/
if (!refcount_release(&object->ref_count)) {
if (object->ref_count > 1 ||
- object->shadow_count == 0) {
+ atomic_load_int(&object->shadow_count) == 0) {
if ((object->flags & OBJ_ANON) != 0 &&
object->ref_count == 1)
vm_object_set_flag(object,
@@ -719,6 +721,14 @@ vm_object_destroy(vm_object_t object)
uma_zfree(obj_zone, object);
}
+static void
+vm_object_sub_shadow(vm_object_t object)
+{
+ KASSERT(object->shadow_count >= 1,
+ ("object %p sub_shadow count zero", object));
+ atomic_subtract_int(&object->shadow_count, 1);
+}
+
static void
vm_object_backing_remove_locked(vm_object_t object)
{
@@ -731,9 +741,9 @@ vm_object_backing_remove_locked(vm_object_t object)
KASSERT((object->flags & OBJ_COLLAPSING) == 0,
("vm_object_backing_remove: Removing collapsing object."));
+ vm_object_sub_shadow(backing_object);
if ((object->flags & OBJ_SHADOWLIST) != 0) {
LIST_REMOVE(object, shadow_list);
- backing_object->shadow_count--;
object->flags &= ~OBJ_SHADOWLIST;
}
object->backing_object = NULL;
@@ -746,13 +756,15 @@ vm_object_backing_remove(vm_object_t object)
VM_OBJECT_ASSERT_WLOCKED(object);
+ backing_object = object->backing_object;
if ((object->flags & OBJ_SHADOWLIST) != 0) {
- backing_object = object->backing_object;
VM_OBJECT_WLOCK(backing_object);
vm_object_backing_remove_locked(object);
VM_OBJECT_WUNLOCK(backing_object);
- } else
+ } else {
object->backing_object = NULL;
+ vm_object_sub_shadow(backing_object);
+ }
}
static void
@@ -761,11 +773,11 @@ vm_object_backing_insert_locked(vm_object_t object, vm_object_t backing_object)
VM_OBJECT_ASSERT_WLOCKED(object);
+ atomic_add_int(&backing_object->shadow_count, 1);
if ((backing_object->flags & OBJ_ANON) != 0) {
VM_OBJECT_ASSERT_WLOCKED(backing_object);
LIST_INSERT_HEAD(&backing_object->shadow_head, object,
shadow_list);
- backing_object->shadow_count++;
object->flags |= OBJ_SHADOWLIST;
}
object->backing_object = backing_object;
@@ -781,8 +793,10 @@ vm_object_backing_insert(vm_object_t object, vm_object_t backing_object)
VM_OBJECT_WLOCK(backing_object);
vm_object_backing_insert_locked(object, backing_object);
VM_OBJECT_WUNLOCK(backing_object);
- } else
+ } else {
object->backing_object = backing_object;
+ atomic_add_int(&backing_object->shadow_count, 1);
+ }
}
/*
@@ -805,6 +819,7 @@ vm_object_backing_insert_ref(vm_object_t object, vm_object_t backing_object)
VM_OBJECT_WUNLOCK(backing_object);
} else {
vm_object_reference(backing_object);
+ atomic_add_int(&backing_object->shadow_count, 1);
object->backing_object = backing_object;
}
}
@@ -831,6 +846,11 @@ vm_object_backing_transfer(vm_object_t object, vm_object_t backing_object)
vm_object_backing_insert_locked(object, new_backing_object);
VM_OBJECT_WUNLOCK(new_backing_object);
} else {
+ /*
+ * shadow_count for new_backing_object is left
+ * unchanged, its reference provided by backing_object
+ * is replaced by object.
+ */
object->backing_object = new_backing_object;
backing_object->backing_object = NULL;
}
@@ -1924,9 +1944,9 @@ vm_object_collapse(vm_object_t object)
return;
KASSERT(object->ref_count > 0 &&
- object->ref_count > object->shadow_count,
+ object->ref_count > atomic_load_int(&object->shadow_count),
("collapse with invalid ref %d or shadow %d count.",
- object->ref_count, object->shadow_count));
+ object->ref_count, atomic_load_int(&object->shadow_count)));
KASSERT((backing_object->flags &
(OBJ_COLLAPSING | OBJ_DEAD)) == 0,
("vm_object_collapse: Backing object already collapsing."));
@@ -1940,9 +1960,10 @@ vm_object_collapse(vm_object_t object)
* all the resident pages in the entire backing object.
*/
if (backing_object->ref_count == 1) {
- KASSERT(backing_object->shadow_count == 1,
+ KASSERT(atomic_load_int(&backing_object->shadow_count)
+ == 1,
("vm_object_collapse: shadow_count: %d",
- backing_object->shadow_count));
+ atomic_load_int(&backing_object->shadow_count)));
vm_object_pip_add(object, 1);
vm_object_set_flag(object, OBJ_COLLAPSING);
vm_object_pip_add(backing_object, 1);
@@ -2510,7 +2531,7 @@ bool
vm_object_is_active(vm_object_t obj)
{
- return (obj->ref_count > obj->shadow_count);
+ return (obj->ref_count > atomic_load_int(&obj->shadow_count));
}
static int
@@ -2565,7 +2586,7 @@ vm_object_list_handler(struct sysctl_req *req, bool swap_only)
kvo->kvo_size = ptoa(obj->size);
kvo->kvo_resident = obj->resident_page_count;
kvo->kvo_ref_count = obj->ref_count;
- kvo->kvo_shadow_count = obj->shadow_count;
+ kvo->kvo_shadow_count = atomic_load_int(&obj->shadow_count);
kvo->kvo_memattr = obj->memattr;
kvo->kvo_active = 0;
kvo->kvo_inactive = 0;
@@ -2779,7 +2800,7 @@ DB_SHOW_COMMAND(object, vm_object_print_static)
object->resident_page_count, object->ref_count, object->flags,
object->cred ? object->cred->cr_ruid : -1, (uintmax_t)object->charge);
db_iprintf(" sref=%d, backing_object(%d)=(%p)+0x%jx\n",
- object->shadow_count,
+ atomic_load_int(&object->shadow_count),
object->backing_object ? object->backing_object->ref_count : 0,
object->backing_object, (uintmax_t)object->backing_object_offset);