Re: [PATCH v8 03/14] rust: sync: add `Arc::as_ptr`

[Benno Lossin <benno.lossin@proton.me>]

On 18.02.25 14:27, Andreas Hindborg wrote:
> Add a method to get a pointer to the data contained in an `Arc`.
> 
> Reviewed-by: Lyude Paul <lyude@redhat.com>
> Reviewed-by: Alice Ryhl <aliceryhl@google.com>
> Signed-off-by: Andreas Hindborg <a.hindborg@kernel.org>
> ---

Reviewed-by: Benno Lossin <benno.lossin@proton.me>

---
Cheers,
Benno

> 
> This is a dependency for:
> 
> rust: hrtimer: implement `HrTimerPointer` for `Arc`
> ---
>  rust/kernel/sync/arc.rs | 13 +++++++++++--
>  1 file changed, 11 insertions(+), 2 deletions(-)
> 
> diff --git a/rust/kernel/sync/arc.rs b/rust/kernel/sync/arc.rs
> index 3cefda7a43725..1dfa75714f9d6 100644
> --- a/rust/kernel/sync/arc.rs
> +++ b/rust/kernel/sync/arc.rs
> @@ -246,6 +246,15 @@ pub fn into_raw(self) -> *const T {
>          unsafe { core::ptr::addr_of!((*ptr).data) }
>      }
> 
> +    /// Return a raw pointer to the data in this arc.
> +    pub fn as_ptr(this: &Self) -> *const T {
> +        let ptr = this.ptr.as_ptr();
> +
> +        // SAFETY: As `ptr` points to a valid allocation of type `ArcInner`,
> +        // field projection to `data`is within bounds of the allocation.
> +        unsafe { core::ptr::addr_of!((*ptr).data) }
> +    }
> +
>      /// Recreates an [`Arc`] instance previously deconstructed via [`Arc::into_raw`].
>      ///
>      /// # Safety
> @@ -539,11 +548,11 @@ unsafe fn new(inner: NonNull<ArcInner<T>>) -> Self {
>      }
> 
>      /// Creates an [`ArcBorrow`] to an [`Arc`] that has previously been deconstructed with
> -    /// [`Arc::into_raw`].
> +    /// [`Arc::into_raw`] or [`Arc::as_ptr`].
>      ///
>      /// # Safety
>      ///
> -    /// * The provided pointer must originate from a call to [`Arc::into_raw`].
> +    /// * The provided pointer must originate from a call to [`Arc::into_raw`] or [`Arc::as_ptr`].
>      /// * For the duration of the lifetime annotated on this `ArcBorrow`, the reference count must
>      ///   not hit zero.
>      /// * For the duration of the lifetime annotated on this `ArcBorrow`, there must not be a
> 
> --
> 2.47.0
> 
>