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

[Andreas Hindborg <nmi@metaspace.dk>]

Boqun Feng <boqun.feng@gmail.com> writes:

> On Wed, Mar 13, 2024 at 11:02:23AM -0700, Bart Van Assche wrote:
>> On 3/13/24 04:05, Andreas Hindborg wrote:
>> > This is the second version of the Rust block device driver API and the Rust null
>> > block driver. The context and motivation can be seen in cover letter of the RFC
>> > v1 [1]. If more context is required, a talk about this effort was recorded at
>> > LPC [2]. I hope to be able to discuss this series at LSF this year [3].
>> 
>> Memory safety may land in C++ in the near future (see also
>> https://herbsutter.com/2024/03/). If memory-safe C++ or memory-safe C
>> would be adopted in the kernel, it would allow writing memory-safe
>> drivers without having to add complicated bindings between existing C
>
> I honestly doubt it, memory-safe is not free, basically you will still
> want unsafe part for the performance reason (or interacting with
> hardware), and provide a safe API for driver development. I don't think
> that part will be gone with a memory-safe C++. So the complication still
> exists. But I'm happy to be proved wrong ;-)

I think it is great that people are starting to realize that bringing
memory safety to other systems languages is a good idea. But from one
person blogging about it to things being ready for production is a long
journey. Language designers have to design ways to express the new
semantics, standards committees has to agree, compiler engineers have to
build and test their compilers. Probably we need a few cycles of this to
get things right. At any rate, it is going to take a while.

Second, as Boqun is saying, interfacing the unsafe C part of the kernel
with memory safe C++ is going to require the same complicated
abstraction logic as the safe Rust APIs are bringing. The complexity in
bringing Rust to the kernel is not coming from interfacing a foreign
language. It stems from the inherent difficulty in designing memory safe
wrappers around unsafe C APIs.

Best regards,
Andreas