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From: Andreas Hindborg <a.hindborg@kernel.org>
To: Gary Guo <gary@garyguo.net>, Oliver Mangold <oliver.mangold@pm.me>
Cc: Miguel Ojeda <ojeda@kernel.org>, Alex Gaynor <alex.gaynor@gmail.com>,
 Boqun Feng <boqun.feng@gmail.com>, =?utf-8?Q?Bj=C3=B6rn?= Roy Baron
 <bjorn3_gh@protonmail.com>, Alice
 Ryhl <aliceryhl@google.com>, Trevor Gross <tmgross@umich.edu>, Benno Lossin
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 <maarten.lankhorst@linux.intel.com>, Maxime Ripard <mripard@kernel.org>,
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 Simona Vetter <simona@ffwll.ch>, Alexander Viro <viro@zeniv.linux.org.uk>,
 Christian Brauner <brauner@kernel.org>, Jan Kara <jack@suse.cz>, Lorenzo
 Stoakes <lorenzo.stoakes@oracle.com>, "Liam R. Howlett"
 <Liam.Howlett@oracle.com>, Viresh Kumar <vireshk@kernel.org>, Nishanth
 Menon <nm@ti.com>, Stephen Boyd <sboyd@kernel.org>, Bjorn Helgaas
 <bhelgaas@google.com>, Krzysztof =?utf-8?Q?Wilczy=C5=84ski?=
 <kwilczynski@kernel.org>, Paul
 Moore <paul@paul-moore.com>, Serge Hallyn <sergeh@kernel.org>, Asahi Lina
 <lina+kernel@asahilina.net>, rust-for-linux@vger.kernel.org,
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Subject: Re: [PATCH v13 2/4] rust: `AlwaysRefCounted` is renamed to
 `RefCounted`.
In-Reply-To: <20251201160030.6956a834.gary@garyguo.net>
References: <20251117-unique-ref-v13-0-b5b243df1250@pm.me>
 <20251117-unique-ref-v13-2-b5b243df1250@pm.me>
 <20251201160030.6956a834.gary@garyguo.net>
Date: Mon, 02 Feb 2026 10:48:39 +0100
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Gary Guo <gary@garyguo.net> writes:

> On Mon, 17 Nov 2025 10:07:57 +0000
> Oliver Mangold <oliver.mangold@pm.me> wrote:
>
>> `AlwaysRefCounted` will become a marker trait to indicate that it is
>> allowed to obtain an `ARef<T>` from a `&T`, which cannot be allowed for
>> types which are also Ownable.
>
> The message needs a rationale for making the change rather than relying
> on the reader to deduce so.
>
> For example:
>
> 	There are types where it may both be referenced counted in some
> 	cases and owned in other. 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.

Thanks, I'll mix this in with the one I sent to Daniel.


Best regards,
Andreas Hindborg