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

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Message-ID: <CANiq72kgu+qKBFOUfcsF9fJkq78p+uBA6KAnpY1Uz5McT0y=SA@mail.gmail.com>
Date: Wed, 28 May 2025 12:51:55 +0200
From: Miguel Ojeda <miguel.ojeda.sandonis@...il.com>
To: Pekka Ristola <pekkarr@...tonmail.com>
Cc: Alexander Viro <viro@...iv.linux.org.uk>, Christian Brauner <brauner@...nel.org>, 
	Miguel Ojeda <ojeda@...nel.org>, Alex Gaynor <alex.gaynor@...il.com>, Jan Kara <jack@...e.cz>, 
	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>, 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 10:49 PM Pekka Ristola <pekkarr@...tonmail.com> 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>

Thanks Pekka, both patches look good to me. I will close the issue
when Christian applies them (or if I should take them, that is good
too).

Cheers,
Miguel