On 6/24/2022 1:48 AM, Jason Gunthorpe wrote:
On Thu, Jun 16, 2022 at 12:59:47AM +0530, Kirti Wankhede wrote:
@@ -110,7 +110,7 @@ static struct mdev_type *add_mdev_supported_type(struct mdev_parent *parent,
type->kobj.kset = parent->mdev_types_kset;
type->parent = parent;
/* Pairs with the put in mdev_type_release() */
- mdev_get_parent(parent);
+ get_device(parent->dev);
type->type_group_id = type_group_id;
Here device reference is held and release multiple times for each mdev_type.
It should be held once from mdev_register_parent() and released from
mdev_unregister_parent().
It doesn't make any sense to put a paired references in the
register/unregister on the struct device - the caller is already
required to hold a reference until unregister completes.
then this need to be documented in the comment above.
The reason this is here is because the type->parent is used in a few
places and is put back in release:
@@ -81,7 +81,7 @@ static void mdev_type_release(struct kobject *kobj)
pr_debug("Releasing group %s\n", kobj->name);
/* Pairs with the get in add_mdev_supported_type() */
- mdev_put_parent(type->parent);
+ put_device(type->parent->dev);
kfree(type);
}
If this was a simple sysfs kobj with only a show/store we wouldn't
need to do anything as the natural kobj parentage holds a ref up to
the struct device - but this kobj is used internally, ie dependent
from mdev_device_create(), independently of the normal sysfs
life-cycle so that doesn't protect enough either.
Life span of 'type' is from mdev_register_device to
mdev_unregister_device. If device/parent is being unregistered then only
types are removed, so referencing 'type' from mdev_device_create() is
still safe. Therefore, parent device's reference should be held and
release from register-unregister call.
Thanks,
Kirti
