linux-kernel - Re: [PATCH v5 4/4] rust: samples: Add debugfs sample

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Message-Id: <D9WLTFASYNN8.CDM0HJKG6RR9@kernel.org>
Date: Thu, 15 May 2025 10:50:43 +0200
From: "Benno Lossin" <lossin@...nel.org>
To: "Matthew Maurer" <mmaurer@...gle.com>
Cc: "Danilo Krummrich" <dakr@...nel.org>, "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" <benno.lossin@...ton.me>,
 "Andreas Hindborg" <a.hindborg@...nel.org>, "Alice Ryhl"
 <aliceryhl@...gle.com>, "Trevor Gross" <tmgross@...ch.edu>, "Greg
 Kroah-Hartman" <gregkh@...uxfoundation.org>, "Rafael J. Wysocki"
 <rafael@...nel.org>, "Sami Tolvanen" <samitolvanen@...gle.com>, "Timur
 Tabi" <ttabi@...dia.com>, <linux-kernel@...r.kernel.org>,
 <rust-for-linux@...r.kernel.org>
Subject: Re: [PATCH v5 4/4] rust: samples: Add debugfs sample

On Thu May 15, 2025 at 12:08 AM CEST, Matthew Maurer wrote:
> Yes, this is also an issue when it comes to attaching data to debugfs
> if you look at the WIP patchset [1]. If we do end up deciding to try
> to do self-referential structs for users (I'd rather not, but I
> understand I don't have the deciding vote here), I'd strongly suggest
> considering self_cell [2] as a model instead of ouroboros - there are
> structural UB issues [3] with ouroboros that are unlikely to be
> resolved, and the author of ouroboros encourages use of self_cell
> instead [4]

I do not think we should add something that allows us to have
self-referential structs. I only mentioned ouroboros, because in theory
it's possible to do in Rust, but we shouldn't do it.

---
Cheers,
Benno

> [1]: https://lore.kernel.org/all/20250506-debugfs-rust-attach-v2-0-c6f88be3890a@google.com/
> [2]: https://docs.rs/self_cell/latest/self_cell/
> [3]: https://github.com/rust-lang/miri/issues/2844#issuecomment-1510577943
> [4]: https://github.com/someguynamedjosh/ouroboros/issues/88