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

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Message-ID: <aIyFjU67jPkK1BUt@google.com>
Date: Fri, 1 Aug 2025 09:14:53 +0000
From: Alice Ryhl <aliceryhl@...gle.com>
To: Danilo Krummrich <dakr@...nel.org>
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, 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 Thu, Jul 31, 2025 at 05:48:06PM +0200, Danilo Krummrich wrote:
> aligned_size() dates back to when Rust did support kmalloc() only, but
> is now used in ReallocFunc::call() and hence for all allocators.
> 
> However, the additional padding applied by aligned_size() is only
> required by the kmalloc() allocator backend.
> 
> Hence, replace aligned_size() with Kmalloc::aligned_layout() and use it
> for the affected allocators, i.e. kmalloc() and kvmalloc(), only.
> 
> While at it, make Kmalloc::aligned_layout() public, such that Rust
> abstractions, which have to call subsystem specific kmalloc() based
> allocation primitives directly, can make use of it.
> 
> Fixes: 8a799831fc63 ("rust: alloc: implement `ReallocFunc`")
> Signed-off-by: Danilo Krummrich <dakr@...nel.org>

I guess vmalloc handles alignment in a different way ... ok makes sense
to me.

Reviewed-by: Alice Ryhl <aliceryhl@...gle.com>