linux-kernel - Re: [PATCH] rust: mm: Mark VmaNew as transparent

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Message-ID: <CAH5fLgi4idH+bU-fQm-kup66+-oF2MkH5CDWp0jguHbkLHqU4Q@mail.gmail.com>
Date: Tue, 12 Aug 2025 15:36:06 +0200
From: Alice Ryhl <aliceryhl@...gle.com>
To: Baptiste Lepers <baptiste.lepers@...il.com>, Andrew Morton <akpm@...ux-foundation.org>
Cc: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>, "Liam R. Howlett" <Liam.Howlett@...cle.com>, 
	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>, 
	Trevor Gross <tmgross@...ch.edu>, Danilo Krummrich <dakr@...nel.org>, Jann Horn <jannh@...gle.com>, 
	linux-mm@...ck.org, rust-for-linux@...r.kernel.org, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] rust: mm: Mark VmaNew as transparent

On Tue, Aug 12, 2025 at 3:29 PM Baptiste Lepers
<baptiste.lepers@...il.com> wrote:
>
> Unsafe code in VmaNew's methods assumes that the type has the same
> layout as the inner `bindings::vm_area_struct`. This is not guaranteed by
> the default struct representation in Rust, but requires specifying the
> `transparent` representation.

Right. It's the case that the layout matches in practice, but we
should use repr(transparent) so that rustc guarantees it. Thanks!

> Fixes: dcb81aeab406e ("mm: rust: add VmaNew for f_ops->mmap()")
> Signed-off-by: Baptiste Lepers <baptiste.lepers@...il.com>

Andrew, can you pick this up? Thanks!

Reviewed-by: Alice Ryhl <aliceryhl@...gle.com>