linux-kernel - Re: [PATCH 1/4] rust: alloc: replace aligned_size() with Kmalloc::aligned

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Message-Id: <DC492K7AA12K.2K9H9SPMPI2Y8@kernel.org>
Date: Sun, 17 Aug 2025 01:44:41 +0200
From: "Danilo Krummrich" <dakr@...nel.org>
To: "Miguel Ojeda" <miguel.ojeda.sandonis@...il.com>
Cc: <lorenzo.stoakes@...cle.com>, <vbabka@...e.cz>,
 <Liam.Howlett@...cle.com>, <urezki@...il.com>, <ojeda@...nel.org>,
 <alex.gaynor@...il.com>, <boqun.feng@...il.com>, <gary@...yguo.net>,
 <bjorn3_gh@...tonmail.com>, <lossin@...nel.org>, <a.hindborg@...nel.org>,
 <aliceryhl@...gle.com>, <tmgross@...ch.edu>,
 <maarten.lankhorst@...ux.intel.com>, <mripard@...nel.org>,
 <tzimmermann@...e.de>, <airlied@...il.com>, <simona@...ll.ch>,
 <rust-for-linux@...r.kernel.org>, <dri-devel@...ts.freedesktop.org>,
 <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/4] rust: alloc: replace aligned_size() with
 Kmalloc::aligned_layout()

On Sat Aug 16, 2025 at 10:40 PM CEST, Miguel Ojeda wrote:
> On Thu, Jul 31, 2025 at 5:49 PM Danilo Krummrich <dakr@...nel.org> wrote:
>>
>> +impl Kmalloc {
>> +    /// Returns a [`Layout`] that makes [`Kmalloc`] fulfill the requested size and alignment of
>> +    /// `layout`.
>> +    pub const fn aligned_layout(layout: Layout) -> Layout {
>
> I think this `const fn` here was removed when applying to make it work
> with older compilers, right?

Yes, that's correct.

> I was fixing another `rusttest` thing and noticed while applying
> these. I had a patch to fix it, since we can actually just use the
> feature, and then I noticed it wasn't in the tree. Since I have it, I
> am attaching it for reference in case the now-stable feature is
> needed, e.g. if you want to make that `const fn` again.

I think it doesn't add much value for this to be a const function anyways, but
maybe it is more useful elsewhere? In that case, I think it also doesn't hurt
to Kmalloc::aligned_layout() const again.