[PATCH v21 4/9] rust: rename `AlwaysRefCounted` to `RefCounted`.

[Gary Guo]

On Fri Sep 11, 2026 at 10:08 AM BST, Alice Ryhl wrote:
> On Thu, Sep 10, 2026 at 11:01 AM Andreas Hindborg <a.hindborg at kernel.org> wrote:
>>
>> From: Oliver Mangold <oliver.mangold at pm.me>
>>
>> There are types where it may both be reference counted in some cases and
>> owned in others. In such cases, obtaining `ARef<T>` from `&T` would be
>> unsound as it allows creation of `ARef<T>` copy from `&Owned<T>`.
>>
>> Therefore, we split `AlwaysRefCounted` into `RefCounted` (which `ARef<T>`
>> would require) and a marker trait to indicate that the type is always
>> reference counted (and not `Ownable`) so the `&T` -> `ARef<T>` conversion
>> is possible.
>>
>> - Rename `AlwaysRefCounted` to `RefCounted`.
>> - Add a new unsafe trait `AlwaysRefCounted`.
>> - Implement the new trait `AlwaysRefCounted` for the newly renamed
>>   `RefCounted` implementations. This leaves functionality of existing
>>   implementers of `AlwaysRefCounted` intact.
>>
>> Suggested-by: Alice Ryhl <aliceryhl at google.com>
>> Reviewed-by: Daniel Almeida <daniel.almeida at collabora.com>
>> Signed-off-by: Oliver Mangold <oliver.mangold at pm.me>
>> [ Andreas: Updated commit message and rebase on rust-next (7.2) ]
>> Acked-by: Igor Korotin <igor.korotin.linux at gmail.com>
>> Acked-by: Danilo Krummrich <dakr at kernel.org>
>> Acked-by: Viresh Kumar <viresh.kumar at linaro.org>
>> Reviewed-by: Gary Guo <gary at garyguo.net>
>> Assisted-by: LLM
>> Co-developed-by: Andreas Hindborg <a.hindborg at kernel.org>
>> Signed-off-by: Andreas Hindborg <a.hindborg at kernel.org>
>
> This has a lot of safety comments of the form "This does not implement
> Ownable, *therefore* it can implement AlwaysRefcounted". But I think
> the safety comment should instead explain that it's okay to create an
> ARef<_> from an &_ for this type. The fact that Ownable is not
> implemented is not sufficient argument.
>
> Alice

Yeah, I think for types that currently implement `AlwaysRefCounted` and does not
have a new `Ownable` form, it should keep saying that "this is always reference
counted".

Best,
Gary