linux-kernel - Re: [PATCH v7 22/26] rust: alloc: implement `Cmalloc` in module allocator

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Message-ID: <ZvluwEpbkLT4LP6Q@pollux>
Date: Sun, 29 Sep 2024 17:14:08 +0200
From: Danilo Krummrich <dakr@...nel.org>
To: Gary Guo <gary@...yguo.net>
Cc: ojeda@...nel.org, alex.gaynor@...il.com, wedsonaf@...il.com,
	boqun.feng@...il.com, bjorn3_gh@...tonmail.com,
	benno.lossin@...ton.me, a.hindborg@...sung.com,
	aliceryhl@...gle.com, akpm@...ux-foundation.org,
	daniel.almeida@...labora.com, faith.ekstrand@...labora.com,
	boris.brezillon@...labora.com, lina@...hilina.net,
	mcanal@...lia.com, zhiw@...dia.com, cjia@...dia.com,
	jhubbard@...dia.com, airlied@...hat.com, ajanulgu@...hat.com,
	lyude@...hat.com, linux-kernel@...r.kernel.org,
	rust-for-linux@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH v7 22/26] rust: alloc: implement `Cmalloc` in module
 allocator_test

On Sat, Sep 28, 2024 at 08:35:52PM +0100, Gary Guo wrote:
> On Thu, 12 Sep 2024 00:52:58 +0200
> Danilo Krummrich <dakr@...nel.org> wrote:
> 
> > So far the kernel's `Box` and `Vec` types can't be used by userspace
> > test cases, since all users of those types (e.g. `CString`) use kernel
> > allocators for instantiation.
> > 
> > In order to allow userspace test cases to make use of such types as
> > well, implement the `Cmalloc` allocator within the allocator_test module
> > and type alias all kernel allocators to `Cmalloc`. The `Cmalloc`
> > allocator uses libc's realloc() function as allocator backend.
> 
> I think this needs an explaination of why it needs a complex
> implementation instead of just using aligned_alloc and free.

The reason basically is that there's no `aligned_realloc` in libc. Anyways, it's
gonna simplified by the introduction of `old_layout`.

> 
> > 
> > Signed-off-by: Danilo Krummrich <dakr@...nel.org>
> > ---
> >  rust/kernel/alloc/allocator_test.rs | 193 +++++++++++++++++++++++++++-
> >  1 file changed, 186 insertions(+), 7 deletions(-)
>