linux-kernel - Re: [PATCH] rust: init: fix `Zeroable` implementation for `Option<NonNull<T>>` and `Option<KBox<T>>`

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Message-ID: <878qpj71k7.fsf@kernel.org>
Date: Wed, 05 Mar 2025 19:52:08 +0100
From: Andreas Hindborg <a.hindborg@...nel.org>
To: "Benno Lossin" <benno.lossin@...ton.me>
Cc: "Miguel Ojeda" <ojeda@...nel.org>,  "Alex Gaynor"
 <alex.gaynor@...il.com>,  "Boqun Feng" <boqun.feng@...il.com>,  "Gary Guo"
 <gary@...yguo.net>,  Björn Roy Baron
 <bjorn3_gh@...tonmail.com>,  "Alice
 Ryhl" <aliceryhl@...gle.com>,  "Trevor Gross" <tmgross@...ch.edu>,
  <stable@...r.kernel.org>,  <rust-for-linux@...r.kernel.org>,
  <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] rust: init: fix `Zeroable` implementation for
 `Option<NonNull<T>>` and `Option<KBox<T>>`

"Benno Lossin" <benno.lossin@...ton.me> writes:

> According to [1], `NonNull<T>` and `#[repr(transparent)]` wrapper types
> such as our custom `KBox<T>` have the null pointer optimization only if
> `T: Sized`. Thus remove the `Zeroable` implementation for the unsized
> case.
>
> Link: https://doc.rust-lang.org/stable/std/option/index.html#representation [1]
> Cc: stable@...r.kernel.org # v6.12+ (a custom patch will be needed for 6.6.y)
> Fixes: 38cde0bd7b67 ("rust: init: add `Zeroable` trait and `init::zeroed` function")
> Signed-off-by: Benno Lossin <benno.lossin@...ton.me>
> ---

Reviewed-by: Andreas Hindborg <a.hindborg@...nel.org>


Best regards,
Andreas Hindborg