linux-kernel - Re: [PATCH v2 2/5] rust: maple

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Message-ID: <CANiq72=ZZ7+tMi_XsRKunGAqm_v+kehFqzpEMMqm2qcTvzA9Mw@mail.gmail.com>
Date: Fri, 22 Aug 2025 13:26:27 +0200
From: Miguel Ojeda <miguel.ojeda.sandonis@...il.com>
To: Danilo Krummrich <dakr@...nel.org>
Cc: Alice Ryhl <aliceryhl@...gle.com>, Andrew Morton <akpm@...ux-foundation.org>, 
	"Liam R. Howlett" <Liam.Howlett@...cle.com>, Lorenzo Stoakes <lorenzo.stoakes@...cle.com>, 
	Miguel Ojeda <ojeda@...nel.org>, Andrew Ballance <andrewjballance@...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>, linux-kernel@...r.kernel.org, 
	maple-tree@...ts.infradead.org, rust-for-linux@...r.kernel.org, 
	linux-mm@...ck.org
Subject: Re: [PATCH v2 2/5] rust: maple_tree: add MapleTree

On Fri, Aug 22, 2025 at 1:05 PM Danilo Krummrich <dakr@...nel.org> wrote:
>
> We should probably check if we can get a clippy warning in place for this.

There is https://rust-lang.github.io/rust-clippy/master/index.html#unwrap_used,
which covers all cases.

> we could also write
>
>         assert!(tree
>             .insert(100, the_answer, GFP_KERNEL)
>             .is_err_and(|e| e.cause == InsertErrorKind::Occupied));

If we want to use the Clippy lint, i.e. go hard on avoiding all kinds
of `unwrap()`s, then that is fine.

But I wouldn't do it just for the sake of avoiding a few
`unwrap_err()`s within `assert!`s -- I don't think there is going to
be a problem of having a lot of people concluding it is OK to panic
the kernel in general just because they see an `unwrap_err()` within
an `assert!` -- the `assert!` itself could be also understood as
panicking, after all, and we really don't want to ban `assert!`s on
examples.

Now, if we do get something else out of it, like enforcing no
`unwrap()`s (still bypassable with `allow` etc. if needed) and thus
removing a class of errors, then that sounds worthier to me.

Thanks!

Cheers,
Miguel