Re: [PATCH v11 0/4] support large align and nid in Rust allocators

[Danilo Krummrich <dakr@kernel.org>]

On Tue, Jul 08, 2025 at 11:58:06AM +0100, Lorenzo Stoakes wrote:
> +cc Liam
> 
> Hi guys,
> 
> We have a section in MAINTAINERS for mm rust (MEMORY MANAGEMENT - RUST), so
> it's slightly concerning to find a series (at v11!) like this that changes
> mm-related stuff and it involves files not listed there and nobody bothered
> to cc- the people listed there.

What files are you referring to? Are you referring to:

	rust/kernel/alloc.rs
	rust/kernel/alloc/*

If so, they're indeed not under the "MEMORY MANAGEMENT - RUST" entry, which
so far seems correct.

Please also note that we had "RUST [ALLOC]" before "MEMORY MANAGEMENT - RUST"
did exist.

> I can fully understand there being some process fail here meaning you
> missed it - fine if so - but let's fix it please moving forwards.

I agree that this series should have a couple more people in Cc.

Given the existing entries in the MAINTAINERS file the Rust parts seems to be
correct though.

> It's really important to me that the rust efforts in mm are collaborative -
> I really believe in your mission (well - for me it's about the compiler
> _helping_ me not shooting me in the foot :) - and have put substantial
> effort in assisting initial work there. So let's make sure we're
> collaborative in both directions please.

AFAICT, those efforts are collaborative.

Back then I sent patches to introduce vrealloc() and improve and align
kvrealloc() and krealloc() [1]; it was also mentioned that this was, besides the
other advantages, prerequisite work for the Rust allocator patch series [2].

The subsequent Rust allocator patch series [2] was also sent to Andrew and the
-mm mailing list; the previous code replaced by this series was maintained under
the "RUST" entry in the maintainers file.

With the introduction of the new Rust allocator code I took over maintainership.

So, Andrew is aware of the Rust allocator tree, please see also [3].

[1] https://lore.kernel.org/all/20240722163111.4766-1-dakr@kernel.org/
[2] https://lore.kernel.org/all/20241004154149.93856-1-dakr@kernel.org/
[3] https://lore.kernel.org/all/20250625143450.2afc473fc0e7124a5108c187@linux-foundation.org/

> We have rust/kernel/mm/ under MEMORY MANAGEMENT - RUST too, I'm not au fait
> with your approach to structuring in these folders but seems to me these
> helpers should be there? I may be unaware of some rust aspect of this
> however.

The Rust allocator module is a user of exactly three functions of mm, i.e.
krealloc(), vrealloc(), kvrealloc(), with a thin abstraction layer for those
three allocator backends. Everything else is rather Rust core infrastructure
than mm infrastructure.

> Can we please add these files to this section and in future cc people
> listed there? We're here to help!

What's your proposal regarding maintainership? Are you asking me to drop it to
"MEMORY MANAGEMENT - RUST"?

> A side-note I wonder if we also need to put specific files also in relevant
> mm sections? E.g. the slab helper should also be put under the slab section
> perhaps?

Yes, we could. But in the end all Rust helper functions are transparent
wrappers, simply forwarding a function call *without* any additional logic.
They don't really require maintainence effort, and, in the end, are just
trivial boilerplate.