linux-kernel - Re: [PATCH v2] rust: list: Add unsafe for container

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Message-ID: <CANiq72md+0Lerj+kqr6QiU6ySR3XjRzmuBiLjkpWWieM72wyeQ@mail.gmail.com>
Date: Tue, 18 Nov 2025 09:20:08 +0100
From: Miguel Ojeda <miguel.ojeda.sandonis@...il.com>
To: Philipp Stanner <phasta@...nel.org>
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>, 
	Benno Lossin <lossin@...nel.org>, Andreas Hindborg <a.hindborg@...nel.org>, 
	Alice Ryhl <aliceryhl@...gle.com>, Trevor Gross <tmgross@...ch.edu>, 
	Danilo Krummrich <dakr@...nel.org>, Tamir Duberstein <tamird@...il.com>, 
	Christian Schrefl <chrisi.schrefl@...il.com>, rust-for-linux@...r.kernel.org, 
	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Subject: Re: [PATCH v2] rust: list: Add unsafe for container_of

On Tue, Nov 18, 2025 at 8:29 AM Philipp Stanner <phasta@...nel.org> wrote:
>
> For unknown reasons, that problem was so far not visible and only gets
> visible once one utilizes the list implementation from within the core
> crate:

What do you mean by "unknown reasons"? The reason is known -- please
refer to my message in the other thread. It should be mentioned in the
log, including the link to the compiler issue.

Also, I assume you meant `kernel` crate, not `core`.

> Cc: stable@...r.kernel.org # v6.17+

No need to mention the kernel version if the Fixes tags implies it. In
fact, it is more confusing, since it looks like there is a version
where it should not be applied to.

> -                let container = $crate::container_of!(
> +                let container = unsafe { $crate::container_of!(
>                      links_field, $crate::list::ListLinksSelfPtr<Self, $num>, inner
> -                );
> +                ) };

Unsafe blocks require `// SAFETY: ...` comments.

Also, please double-check if this is the formatting that `rustfmt` would use.

Thanks!

Cheers,
Miguel