Re: [RFC PATCH 0/5] Rust block device driver API and null block driver

From: Andreas Hindborg <nmi@metaspace.dk>
To: Bart Van Assche <bvanassche@acm.org>
Cc: "Philipp Stanner" <pstanner@redhat.com>,
	"Jens Axboe" <axboe@kernel.dk>, "Christoph Hellwig" <hch@lst.de>,
	"Keith Busch" <kbusch@kernel.org>,
	"Damien Le Moal" <Damien.LeMoal@wdc.com>,
	"Hannes Reinecke" <hare@suse.de>,
	"linux-block@vger.kernel.org" <linux-block@vger.kernel.org>,
	"Andreas Hindborg" <a.hindborg@samsung.com>,
	"Niklas Cassel" <Niklas.Cassel@wdc.com>,
	"Greg KH" <gregkh@linuxfoundation.org>,
	"Matthew Wilcox" <willy@infradead.org>,
	"Miguel Ojeda" <ojeda@kernel.org>,
	"Alex Gaynor" <alex.gaynor@gmail.com>,
	"Wedson Almeida Filho" <wedsonaf@gmail.com>,
	"Boqun Feng" <boqun.feng@gmail.com>,
	"Gary Guo" <gary@garyguo.net>,
	"Björn Roy Baron" <bjorn3_gh@protonmail.com>,
	"Benno Lossin" <benno.lossin@proton.me>,
	"Alice Ryhl" <aliceryhl@google.com>,
	"Chaitanya Kulkarni" <chaitanyak@nvidia.com>,
	"Luis Chamberlain" <mcgrof@kernel.org>,
	"Yexuan Yang" <1182282462@bupt.edu.cn>,
	"Sergio González Collado" <sergio.collado@gmail.com>,
	"Joel Granados" <j.granados@samsung.com>,
	"Pankaj Raghav (Samsung)" <kernel@pankajraghav.com>,
	"Daniel Gomez" <da.gomez@samsung.com>,
	"open list" <linux-kernel@vger.kernel.org>,
	"rust-for-linux@vger.kernel.org" <rust-for-linux@vger.kernel.org>,
	"lsf-pc@lists.linux-foundation.org"
	<lsf-pc@lists.linux-foundation.org>,
	"gost.dev@samsung.com" <gost.dev@samsung.com>
Subject: Re: [RFC PATCH 0/5] Rust block device driver API and null block driver
Date: Thu, 14 Mar 2024 18:43:56 +0100	[thread overview]
Message-ID: <87y1akso83.fsf@metaspace.dk> (raw)
In-Reply-To: <5f502f91-0450-454d-ae8f-36223920532e@acm.org> (Bart Van Assche's message of "Thu, 14 Mar 2024 10:03:28 -0700")

Hi Bart,

Bart Van Assche <bvanassche@acm.org> writes:
> On 3/14/24 05:14, Philipp Stanner wrote:
>> On Wed, 2024-03-13 at 11:02 -0700, Bart Van Assche wrote:

[...]

>> One of the stronger arguments behind the push for Rust is that the
>> language by design forces you to obey, because otherwise the compiler
>> will just reject building.
>
> Rust has a very significant disadvantage that memory-safe C/C++ won't
> have: supporting Rust means adding Rust bindings for all C functions
> called from Rust code. This forces everyone who wants to change an
> interface to also change the Rust bindings and hence will make it
> harder to maintain the Linux kernel in its entirety.

I think you might be missing a key point here. We actually generate Rust
bindings to the existing C kernel automatically. No hand editing
required, except for some corner cases we currently have with static
methods and certain macros. If we just wanted to call the C APIa
directly, there would be no engineering required. The main reason to
deploy Rust would also go away, we might as well stay in C.

The actual engineering effort goes into building memory safe versions of
the C APIs. This requirement will not magically go away, no matter what
memory safe language (or language extensions) your use to interface the
existing unsafe C APIs.

Best regards,
Andreas