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 <da7b815d-3da8-38e5-9b25-b9cfb6878293@acm.org>
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From:   Andreas Hindborg <nmi@metaspace.dk>
To:     Bart Van Assche <bvanassche@acm.org>
Cc:     Jens Axboe <axboe@kernel.dk>, Christoph Hellwig <hch@lst.de>,
        Keith Busch <kbusch@kernel.org>,
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        Hannes Reinecke <hare@suse.de>,
        lsf-pc@lists.linux-foundation.org, rust-for-linux@vger.kernel.org,
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        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>,
        =?utf-8?Q?Bj?= =?utf-8?Q?=C3=B6rn?= Roy Baron 
        <bjorn3_gh@protonmail.com>, Benno Lossin <benno.lossin@proton.me>,
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Subject: Re: [RFC PATCH 00/11] Rust null block driver
Date:   Thu, 04 May 2023 20:15:23 +0200
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Hi Bart,

Bart Van Assche <bvanassche@acm.org> writes:

> On 5/3/23 02:06, Andreas Hindborg wrote:
>> This is an early preview of a null block driver written in Rust.
>
> It is not clear to me why this effort was started? As far as I know the null_blk
> driver is only used by kernel developers for testing kernel changes so end users
> are not affected by bugs in this driver. Additionally, performance of this
> driver is critical since this driver is used to measure block layer performance.
> Does this mean that C is a better choice than Rust for this driver?

I take it you did not read the rest of the cover letter. Let me quote
some of it here:

> A null block driver is a good opportunity to evaluate Rust bindings for the
> block layer. It is a small and simple driver and thus should be simple to reason
> about. Further, the null block driver is not usually deployed in production
> environments. Thus, it should be fairly straight forward to review, and any
> potential issues are not going to bring down any production workloads.
>
> Being small and simple, the null block driver is a good place to introduce the
> Linux kernel storage community to Rust. This will help prepare the community for
> future Rust projects and facilitate a better maintenance process for these
> projects.
>
> The statistics presented in my previous message [1] show that the C null block
> driver has had a significant amount of memory safety related problems in the
> past. 41% of fixes merged for the C null block driver are fixes for memory
> safety issues. This makes the null block driver a good candidate for rewriting
> in Rust.

In relation to performance, it turns out that there is not much of a
difference. For memory safety bugs - I think we are better off without
them, no matter if we are user facing or not.

If it is still unclear to you why this effort was started, please do let
me know and I shall try to clarify further :)

Best regards,
Andreas