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

["Gary Guo" <gary@garyguo.net>]

On Wed Feb 4, 2026 at 11:56 AM GMT, Andreas Hindborg wrote:
> From: Asahi Lina <lina+kernel@asahilina.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@asahilina.net> [1] and Oliver Mangold <oliver.mangold@pm.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@kernel.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@garyguo.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> {}
> +