linux-kernel - Re: [PATCH v3 03/12] rust: xarray: add `contains

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Message-ID: <CAJ-ks9nZuBJnw=AAr68Chhfa+QB=j4OQURKJrnAFJarqw4gZcw@mail.gmail.com>
Date: Wed, 11 Feb 2026 13:24:17 -0500
From: Tamir Duberstein <tamird@...il.com>
To: Andreas Hindborg <a.hindborg@...nel.org>
Cc: 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>, Alice Ryhl <aliceryhl@...gle.com>, 
	Trevor Gross <tmgross@...ch.edu>, Danilo Krummrich <dakr@...nel.org>, 
	Lorenzo Stoakes <lorenzo.stoakes@...cle.com>, "Liam R. Howlett" <Liam.Howlett@...cle.com>, 
	Vlastimil Babka <vbabka@...e.cz>, Andrew Morton <akpm@...ux-foundation.org>, 
	Christoph Lameter <cl@...two.org>, David Rientjes <rientjes@...gle.com>, 
	Roman Gushchin <roman.gushchin@...ux.dev>, Harry Yoo <harry.yoo@...cle.com>, 
	Daniel Gomez <da.gomez@...nel.org>, rust-for-linux@...r.kernel.org, 
	linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH v3 03/12] rust: xarray: add `contains_index` method

On Tue, Feb 10, 2026 at 11:31 PM Andreas Hindborg <a.hindborg@...nel.org> wrote:
>
> Tamir Duberstein <tamird@...il.com> writes:
>
> > On Mon, Feb 9, 2026 at 6:38 AM Andreas Hindborg <a.hindborg@...nel.org> wrote:
> >>
> >> Add a convenience method `contains_index` to check whether an element
> >> exists at a given index in the XArray. This method provides a more
> >> ergonomic API compared to calling `get` and checking for `Some`.
> >>
> >> Signed-off-by: Andreas Hindborg <a.hindborg@...nel.org>
> >
> > As I said in v1 I'm -1 on this change. As gregkh would say: it's hard
> > to review a new API without seeing its user.
>
> I already gave you the user inline [1] and if you wish you can also see
> it in a downstream tree [2]. Gary already explained why this is required
> with the current implementation of the borrow checker [3].

Yeah, that's fine, and the poor ergonomics are IMO a feature - I
should see the ugly `is_some()` call in your code, because it's a
useful signal that something non-obvious is going. This function hides
that, which I think is not better.

>
> Best regards,
> Andreas Hindborg
>
> [1] https://lore.kernel.org/r/87344gh2pk.fsf@t14s.mail-host-address-is-not-set
> [2] https://github.com/metaspace/linux/blob/aa43a6ecb68a785a90e167609aa57c5a0860d123/drivers/block/rnull/disk_storage.rs#L218
> [3] https://lore.kernel.org/r/DFK801ZCI1GD.34GWJ10JZBBBF@garyguo.net
>