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Message-ID: <2021ea8f-a3df-46c6-8fdf-61b1df231773@proton.me>
Date: Sat, 01 Jun 2024 09:15:59 +0000
From: Benno Lossin <benno.lossin@...ton.me>
To: Andreas Hindborg <nmi@...aspace.dk>, Jens Axboe <axboe@...nel.dk>, Christoph Hellwig <hch@....de>, Keith Busch <kbusch@...nel.org>, Damien Le Moal <dlemoal@...nel.org>, Bart Van Assche <bvanassche@....org>, Hannes Reinecke <hare@...e.de>, Ming Lei <ming.lei@...hat.com>, "linux-block@...r.kernel.org" <linux-block@...r.kernel.org>
Cc: Andreas Hindborg <a.hindborg@...sung.com>, Greg KH <gregkh@...uxfoundation.org>, Matthew Wilcox <willy@...radead.org>, Miguel Ojeda <ojeda@...nel.org>, Alex Gaynor <alex.gaynor@...il.com>, Wedson Almeida Filho <wedsonaf@...il.com>, Boqun Feng <boqun.feng@...il.com>, Gary Guo <gary@...yguo.net>, Björn Roy Baron <bjorn3_gh@...tonmail.com>, Alice Ryhl <aliceryhl@...gle.com>, Chaitanya Kulkarni <chaitanyak@...dia.com>, Luis Chamberlain <mcgrof@...nel.org>, Yexuan Yang <1182282462@...t.edu.cn>, Sergio González Collado <sergio.collado@...il.com>, Joel Granados <j.granados@...sung.com>, "Pankaj Raghav (Samsung)" <kernel@...kajraghav.com>, Daniel Gomez <da.gomez@...sung.com>, Niklas Cassel <Niklas.Cassel@....com>, Philipp Stanner <pstanner@...hat.com>, Conor Dooley <conor@...nel.org>, Johannes Thumshirn <Johannes.Thumshirn@....com>, Matias Bjørling <m@...rling.me>, open list <linux-kernel@...r.kernel.org>,
"rust-for-linux@...r.kernel.org" <rust-for-linux@...r.kernel.org>, "lsf-pc@...ts.linux-foundation.org" <lsf-pc@...ts.linux-foundation.org>, "gost.dev@...sung.com" <gost.dev@...sung.com>
Subject: Re: [PATCH v3 2/3] rust: block: add rnull, Rust null_blk implementation
On 01.06.24 10:18, Andreas Hindborg wrote:
> From: Andreas Hindborg <a.hindborg@...sung.com>
>
> This patch adds an initial version of the Rust null block driver.
>
> Signed-off-by: Andreas Hindborg <a.hindborg@...sung.com>
> ---
> drivers/block/Kconfig | 9 +++++
> drivers/block/Makefile | 3 ++
> drivers/block/rnull.rs | 78 ++++++++++++++++++++++++++++++++++++++++++
> 3 files changed, 90 insertions(+)
> create mode 100644 drivers/block/rnull.rs
I left two comments below, but it already seems fine to me:
Reviewed-by: Benno Lossin <benno.lossin@...ton.me>
>
> diff --git a/drivers/block/Kconfig b/drivers/block/Kconfig
> index 5b9d4aaebb81..ed209f4f2798 100644
> --- a/drivers/block/Kconfig
> +++ b/drivers/block/Kconfig
> @@ -354,6 +354,15 @@ config VIRTIO_BLK
> This is the virtual block driver for virtio. It can be used with
> QEMU based VMMs (like KVM or Xen). Say Y or M.
>
> +config BLK_DEV_RUST_NULL
> + tristate "Rust null block driver (Experimental)"
> + depends on RUST
> + help
> + This is the Rust implementation of the null block driver. For now it
> + is only a minimal stub.
> +
> + If unsure, say N.
> +
> config BLK_DEV_RBD
> tristate "Rados block device (RBD)"
> depends on INET && BLOCK
> diff --git a/drivers/block/Makefile b/drivers/block/Makefile
> index 101612cba303..1105a2d4fdcb 100644
> --- a/drivers/block/Makefile
> +++ b/drivers/block/Makefile
> @@ -9,6 +9,9 @@
> # needed for trace events
> ccflags-y += -I$(src)
>
> +obj-$(CONFIG_BLK_DEV_RUST_NULL) += rnull_mod.o
> +rnull_mod-y := rnull.o
> +
> obj-$(CONFIG_MAC_FLOPPY) += swim3.o
> obj-$(CONFIG_BLK_DEV_SWIM) += swim_mod.o
> obj-$(CONFIG_BLK_DEV_FD) += floppy.o
> diff --git a/drivers/block/rnull.rs b/drivers/block/rnull.rs
> new file mode 100644
> index 000000000000..c69ea7e7436e
> --- /dev/null
> +++ b/drivers/block/rnull.rs
> @@ -0,0 +1,78 @@
> +// SPDX-License-Identifier: GPL-2.0
> +
> +//! This is a Rust implementation of the C null block driver.
> +//!
> +//! Supported features:
> +//!
> +//! - blk-mq interface
> +//! - direct completion
> +//! - block size 4k
> +//!
> +//! The driver is not configurable.
> +
> +use kernel::{
> + alloc::flags,
> + block::mq::{
> + self,
> + gen_disk::{self, GenDisk},
> + Operations, TagSet,
> + },
> + error::Result,
> + new_mutex, pr_info,
> + prelude::*,
> + sync::{Arc, Mutex},
> + types::ARef,
> +};
> +
> +module! {
> + type: NullBlkModule,
> + name: "rnull_mod",
> + author: "Andreas Hindborg",
> + license: "GPL v2",
> +}
> +
> +struct NullBlkModule {
> + _disk: Pin<Box<Mutex<GenDisk<NullBlkDevice, gen_disk::Added>>>>,
> +}
> +
> +impl kernel::Module for NullBlkModule {
> + fn init(_module: &'static ThisModule) -> Result<Self> {
> + pr_info!("Rust null_blk loaded\n");
> + let tagset = Arc::pin_init(TagSet::try_new(1, 256, 1), flags::GFP_KERNEL)?;
> +
> + let disk = {
> + let block_size: u16 = 4096;
> + if block_size % 512 != 0 || !(512..=4096).contains(&block_size) {
> + return Err(kernel::error::code::EINVAL);
> + }
> +
> + let mut disk = gen_disk::GenDisk::try_new(tagset)?;
> + disk.set_name(format_args!("rnullb{}", 0))?;
> + disk.set_capacity_sectors(4096 << 11);
> + disk.set_queue_logical_block_size(block_size.into());
> + disk.set_queue_physical_block_size(block_size.into());
> + disk.set_rotational(false);
> + disk.add()
> + }?;
Personally, I would prefer to put the `?` into the line above.
> +
> + let disk = Box::pin_init(new_mutex!(disk, "nullb:disk"), flags::GFP_KERNEL)?;
> +
> + Ok(Self { _disk: disk })
> + }
> +}
> +
> +struct NullBlkDevice;
> +
> +#[vtable]
> +impl Operations for NullBlkDevice {
> + #[inline(always)]
> + fn queue_rq(rq: ARef<mq::Request<Self>>, _is_last: bool) -> Result {
> + mq::Request::end_ok(rq)
> + .map_err(|_e| kernel::error::code::EIO)
> + .expect("Fatal error - expected to be able to end request");
I expected something more along the lines of: "expected to be able to
end request, since `NullBlkDevice` never takes refcounts on Requests and
as such the ARef must be unique, but `end_ok` only fails if that is not
the case". But maybe that would fit better in a comment, what do you
think?
> +
> + Ok(())
> + }
> +
> + fn commit_rqs() {}
> +}
> --
> 2.45.1
>
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