linux-kernel - Re: [PATCH v14 1/9] rust: types: Add Ownable/Owned types

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Message-Id: <DG72BM2I3QKI.1SCBV7WL5B1TG@garyguo.net>
Date: Thu, 05 Feb 2026 13:29:16 +0000
From: "Gary Guo" <gary@...yguo.net>
To: "Andreas Hindborg" <a.hindborg@...nel.org>, "Miguel Ojeda"
 <ojeda@...nel.org>, "Boqun Feng" <boqun.feng@...il.com>, "Gary Guo"
 <gary@...yguo.net>, Björn Roy Baron
 <bjorn3_gh@...tonmail.com>, "Benno Lossin" <lossin@...nel.org>, "Alice
 Ryhl" <aliceryhl@...gle.com>, "Trevor Gross" <tmgross@...ch.edu>, "Danilo
 Krummrich" <dakr@...nel.org>, "Greg Kroah-Hartman"
 <gregkh@...uxfoundation.org>, "Dave Ertman" <david.m.ertman@...el.com>,
 "Ira Weiny" <ira.weiny@...el.com>, "Leon Romanovsky" <leon@...nel.org>,
 "Paul Moore" <paul@...l-moore.com>, "Serge Hallyn" <sergeh@...nel.org>,
 "Rafael J. Wysocki" <rafael@...nel.org>, "David Airlie"
 <airlied@...il.com>, "Simona Vetter" <simona@...ll.ch>, "Alexander Viro"
 <viro@...iv.linux.org.uk>, "Christian Brauner" <brauner@...nel.org>, "Jan
 Kara" <jack@...e.cz>, "Igor Korotin" <igor.korotin.linux@...il.com>,
 "Daniel Almeida" <daniel.almeida@...labora.com>, "Lorenzo Stoakes"
 <lorenzo.stoakes@...cle.com>, "Liam R. Howlett" <Liam.Howlett@...cle.com>,
 "Viresh Kumar" <vireshk@...nel.org>, "Nishanth Menon" <nm@...com>, "Stephen
 Boyd" <sboyd@...nel.org>, "Bjorn Helgaas" <bhelgaas@...gle.com>,
 Krzysztof Wilczyński <kwilczynski@...nel.org>
Cc: <linux-kernel@...r.kernel.org>, <rust-for-linux@...r.kernel.org>,
 <linux-block@...r.kernel.org>, <linux-security-module@...r.kernel.org>,
 <dri-devel@...ts.freedesktop.org>, <linux-fsdevel@...r.kernel.org>,
 <linux-mm@...ck.org>, <linux-pm@...r.kernel.org>,
 <linux-pci@...r.kernel.org>, "Asahi Lina" <lina+kernel@...hilina.net>
Subject: Re: [PATCH v14 1/9] rust: types: Add Ownable/Owned types

On Wed Feb 4, 2026 at 11:56 AM GMT, Andreas Hindborg wrote:
> From: Asahi Lina <lina+kernel@...hilina.net>
>
> By analogy to `AlwaysRefCounted` and `ARef`, an `Ownable` type is a
> (typically C FFI) type that *may* be owned by Rust, but need not be. Unlike
> `AlwaysRefCounted`, this mechanism expects the reference to be unique
> within Rust, and does not allow cloning.
>
> Conceptually, this is similar to a `KBox<T>`, except that it delegates
> resource management to the `T` instead of using a generic allocator.
>
> This change is a derived work based on work by Asahi Lina
> <lina+kernel@...hilina.net> [1] and Oliver Mangold <oliver.mangold@...me>.
>
> Link: https://lore.kernel.org/rust-for-linux/20250202-rust-page-v1-1-e3170d7fe55e@asahilina.net/ [1]
> Signed-off-by: Andreas Hindborg <a.hindborg@...nel.org>
> ---
>  rust/kernel/lib.rs       |   1 +
>  rust/kernel/owned.rs     | 196 +++++++++++++++++++++++++++++++++++++++++++++++
>  rust/kernel/sync/aref.rs |   5 ++
>  rust/kernel/types.rs     |  11 ++-
>  4 files changed, 212 insertions(+), 1 deletion(-)
>
> diff --git a/rust/kernel/lib.rs b/rust/kernel/lib.rs
> index f812cf1200428..96a3fadc3377a 100644
> --- a/rust/kernel/lib.rs
> +++ b/rust/kernel/lib.rs
> @@ -119,6 +119,7 @@
>  pub mod of;
>  #[cfg(CONFIG_PM_OPP)]
>  pub mod opp;
> +pub mod owned;
>  pub mod page;
>  #[cfg(CONFIG_PCI)]
>  pub mod pci;
> diff --git a/rust/kernel/owned.rs b/rust/kernel/owned.rs
> new file mode 100644
> index 0000000000000..fe30580331df9
> --- /dev/null
> +++ b/rust/kernel/owned.rs
> <snip>
> +
> +    /// Get a pinned mutable reference to the data owned by this `Owned<T>`.
> +    pub fn get_pin_mut(&mut self) -> Pin<&mut T> {
> +        // SAFETY: The type invariants guarantee that the object is valid, and that we can safely
> +        // return a mutable reference to it.
> +        let unpinned = unsafe { self.ptr.as_mut() };
> +
> +        // SAFETY: We never hand out unpinned mutable references to the data in
> +        // `Self`, unless the contained type is `Unpin`.
> +        unsafe { Pin::new_unchecked(unpinned) }
> +    }

Probably should be name `as_pin_mut` instead.

With name changed and SOB fixed:

Reviewed-by: Gary Guo <gary@...yguo.net>

Best,
Gary

> +}
> +
> +// SAFETY: It is safe to send an [`Owned<T>`] to another thread when the underlying `T` is [`Send`],
> +// because of the ownership invariant. Sending an [`Owned<T>`] is equivalent to sending the `T`.
> +unsafe impl<T: Ownable + Send> Send for Owned<T> {}
> +
> +// SAFETY: It is safe to send [`&Owned<T>`] to another thread when the underlying `T` is [`Sync`],
> +// because of the ownership invariant. Sending an [`&Owned<T>`] is equivalent to sending the `&T`.
> +unsafe impl<T: Ownable + Sync> Sync for Owned<T> {}
> +