Re: [Qemu-devel] [PATCH v4 1/2] qom: Add can_be_deleted callback to UserCreatableClass

[Igor Mammedov <imammedo@redhat.com>]

On Fri, 27 Mar 2015 13:36:11 +0800
Lin Ma <lma@suse.com> wrote:

> If backends implement the can_be_deleted and it returns false,
> Then the qmp_object_del won't delete the given backends.
> 
> Signed-off-by: Lin Ma <lma@suse.com>
> ---
>  include/qom/object_interfaces.h | 14 ++++++++++++++
>  qmp.c                           |  5 +++++
>  qom/object_interfaces.c         | 15 +++++++++++++++
>  3 files changed, 34 insertions(+)
> 
> diff --git a/include/qom/object_interfaces.h b/include/qom/object_interfaces.h
> index b792283..012b653 100644
> --- a/include/qom/object_interfaces.h
> +++ b/include/qom/object_interfaces.h
> @@ -25,6 +25,8 @@ typedef struct UserCreatable {
>   * UserCreatableClass:
>   * @parent_class: the base class
>   * @complete: callback to be called after @obj's properties are set.
> + * @can_be_deleted: callback to be called before an object is removed
> + * to check if @obj can be removed safely.
>   *
>   * Interface is designed to work with -object/object-add/object_add
>   * commands.
> @@ -47,6 +49,7 @@ typedef struct UserCreatableClass {
>  
>      /* <public> */
>      void (*complete)(UserCreatable *uc, Error **errp);
> +    bool (*can_be_deleted)(UserCreatable *uc, Error **errp);
>  } UserCreatableClass;
>  
>  /**
> @@ -59,4 +62,15 @@ typedef struct UserCreatableClass {
>   * nothing.
>   */
>  void user_creatable_complete(Object *obj, Error **errp);
> +
> +/**
> + * user_creatable_can_be_deleted:
> + * @obj: the object whose can_be_deleted() method is called if defined
> + * @errp: if an error occurs, a pointer to an area to store the error
> + *
> + * Wrapper to call can_be_deleted() method if one of types it's inherited
> + * from implements USER_CREATABLE interface, otherwise the call does
> + * nothing.
> + */
> +bool user_creatable_can_be_deleted(Object *obj, Error **errp);
>  #endif
> diff --git a/qmp.c b/qmp.c
> index c479e77..dc61da1 100644
> --- a/qmp.c
> +++ b/qmp.c
> @@ -711,6 +711,11 @@ void qmp_object_del(const char *id, Error **errp)
>          error_setg(errp, "object id not found");
>          return;
>      }
> +
> +    if (!user_creatable_can_be_deleted(obj, errp)) {
> +        error_setg(errp, "%s is in used, can not be deleted", id);
                                ^^^ is in use || is used
> +        return;
> +    }
>      object_unparent(obj);
>  }
>  
> diff --git a/qom/object_interfaces.c b/qom/object_interfaces.c
> index 6360818..25ae6ca 100644
> --- a/qom/object_interfaces.c
> +++ b/qom/object_interfaces.c
> @@ -18,6 +18,21 @@ void user_creatable_complete(Object *obj, Error **errp)
>      }
>  }
>  
> +bool user_creatable_can_be_deleted(Object *obj, Error **errp)
> +{
> +
> +    UserCreatableClass *ucc;
> +    UserCreatable *uc =
> +        (UserCreatable *)object_dynamic_cast(obj, TYPE_USER_CREATABLE);
direc cast is wron, pls use type specific caster with QOM objects
in this case you can even drop dynamic cast since /objects holds
only TYPE_USER_CREATABLE objects and just do
  UserCreatable *uc = USER_CREATABLE(obj)
you don't check for null pointer anyway

> +
> +    ucc = USER_CREATABLE_GET_CLASS(uc);
> +    if (ucc->can_be_deleted) {
> +        return ucc->can_be_deleted(uc, errp);
> +    } else {
> +        return true;
> +    }
> +}
> +
>  static void register_types(void)
>  {
>      static const TypeInfo uc_interface_info = {