linux-kernel - Re: [PATCH 1/2] rust: file: mark `LocalFile` as `repr(transparent)`

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Message-Id: <DA7WFS13MU9F.349OE3IGIDMBY@kernel.org>
Date: Wed, 28 May 2025 17:29:26 +0200
From: "Benno Lossin" <lossin@...nel.org>
To: "Pekka Ristola" <pekkarr@...tonmail.com>, "Alexander Viro"
 <viro@...iv.linux.org.uk>, "Christian Brauner" <brauner@...nel.org>,
 "Miguel Ojeda" <ojeda@...nel.org>, "Alex Gaynor" <alex.gaynor@...il.com>
Cc: "Jan Kara" <jack@...e.cz>, "Boqun Feng" <boqun.feng@...il.com>, "Gary
 Guo" <gary@...yguo.net>, Björn Roy Baron
 <bjorn3_gh@...tonmail.com>, "Andreas Hindborg" <a.hindborg@...nel.org>,
 "Alice Ryhl" <aliceryhl@...gle.com>, "Trevor Gross" <tmgross@...ch.edu>,
 "Danilo Krummrich" <dakr@...nel.org>, <linux-fsdevel@...r.kernel.org>,
 <rust-for-linux@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/2] rust: file: mark `LocalFile` as `repr(transparent)`

On Tue May 27, 2025 at 10:48 PM CEST, Pekka Ristola wrote:
> Unsafe code in `LocalFile`'s methods assumes that the type has the same
> layout as the inner `bindings::file`. This is not guaranteed by the default
> struct representation in Rust, but requires specifying the `transparent`
> representation.
>
> The `File` struct (which also wraps `bindings::file`) is already marked as
> `repr(transparent)`, so this change makes their layouts equivalent.
>
> Fixes: 851849824bb5 ("rust: file: add Rust abstraction for `struct file`")
> Closes: https://github.com/Rust-for-Linux/linux/issues/1165
> Signed-off-by: Pekka Ristola <pekkarr@...tonmail.com>

Reviewed-by: Benno Lossin <lossin@...nel.org>

---
Cheers,
Benno