linux-kernel - Re: [PATCH v2 1/2] rust: alloc: specify the minimum alignment of each allocator

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Message-ID: <aJxESG0l4-kyUHXg@google.com>
Date: Wed, 13 Aug 2025 07:52:40 +0000
From: Alice Ryhl <aliceryhl@...gle.com>
To: Danilo Krummrich <dakr@...nel.org>
Cc: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>, "Liam R. Howlett" <Liam.Howlett@...cle.com>, 
	Andrew Morton <akpm@...ux-foundation.org>, Matthew Wilcox <willy@...radead.org>, 
	Tamir Duberstein <tamird@...il.com>, Andreas Hindborg <a.hindborg@...nel.org>, 
	Miguel Ojeda <ojeda@...nel.org>, Boqun Feng <boqun.feng@...il.com>, Gary Guo <gary@...yguo.net>, 
	"Björn Roy Baron" <bjorn3_gh@...tonmail.com>, Benno Lossin <lossin@...nel.org>, 
	Trevor Gross <tmgross@...ch.edu>, linux-mm@...ck.org, rust-for-linux@...r.kernel.org, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/2] rust: alloc: specify the minimum alignment of each allocator

On Tue, Aug 12, 2025 at 07:52:35PM +0200, Danilo Krummrich wrote:
> On Mon Aug 11, 2025 at 2:31 PM CEST, Alice Ryhl wrote:
> > diff --git a/rust/kernel/alloc/allocator.rs b/rust/kernel/alloc/allocator.rs
> > index aa2dfa9dca4c309e5a9eafc7da6a8a9bd7b54b11..25fc9f9ae3b4e471a08d77130b374bd1397f7384 100644
> > --- a/rust/kernel/alloc/allocator.rs
> > +++ b/rust/kernel/alloc/allocator.rs
> > @@ -17,6 +17,8 @@
> >  use crate::bindings;
> >  use crate::pr_warn;
> >  
> > +const ARCH_KMALLOC_MINALIGN: usize = bindings::ARCH_KMALLOC_MINALIGN as usize;
> 
> I think this needs the following diff:
> 
> diff --git a/rust/bindings/bindings_helper.h b/rust/bindings/bindings_helper.h
> index 84d60635e8a9..4ad9add117ea 100644
> --- a/rust/bindings/bindings_helper.h
> +++ b/rust/bindings/bindings_helper.h
> @@ -84,6 +84,7 @@
> 
>  /* `bindgen` gets confused at certain things. */
>  const size_t RUST_CONST_HELPER_ARCH_SLAB_MINALIGN = ARCH_SLAB_MINALIGN;
> +const size_t RUST_CONST_HELPER_ARCH_KMALLOC_MINALIGN = ARCH_KMALLOC_MINALIGN;
>  const size_t RUST_CONST_HELPER_PAGE_SIZE = PAGE_SIZE;
>  const gfp_t RUST_CONST_HELPER_GFP_ATOMIC = GFP_ATOMIC;
>  const gfp_t RUST_CONST_HELPER_GFP_KERNEL = GFP_KERNEL;
> diff --git a/rust/kernel/alloc/allocator.rs b/rust/kernel/alloc/allocator.rs
> index 25fc9f9ae3b4..5003907f0240 100644
> --- a/rust/kernel/alloc/allocator.rs
> +++ b/rust/kernel/alloc/allocator.rs
> @@ -17,7 +17,7 @@
>  use crate::bindings;
>  use crate::pr_warn;
> 
> -const ARCH_KMALLOC_MINALIGN: usize = bindings::ARCH_KMALLOC_MINALIGN as usize;
> +const ARCH_KMALLOC_MINALIGN: usize = bindings::ARCH_KMALLOC_MINALIGN;
> 
>  /// The contiguous kernel allocator.
>  ///
> 
> 
> No need to resend I can fix it up when applying the patch.

Hmm. Maybe that depends on the configuration? The constant was generated
for me. Either way, happy with the suggested change.

Alice