From bc5b533b91ef0b8a09fe507e23d1c6c43c1fb0f5 Mon Sep 17 00:00:00 2001
From: Andreas Hindborg <a.hindborg@samsung.com>
Date: Tue, 11 Jun 2024 13:45:50 +0200
Subject: [PATCH] rust: block: add rnull, Rust null_blk implementation
This patch adds an initial version of the Rust null block driver.
Signed-off-by: Andreas Hindborg <a.hindborg@samsung.com>
Reviewed-by: Benno Lossin <benno.lossin@proton.me>
Link: https://lore.kernel.org/r/20240611114551.228679-3-nmi@metaspace.dk
Signed-off-by: Jens Axboe <axboe@kernel.dk>
---
drivers/block/Kconfig | 9 ++++++
drivers/block/Makefile | 3 ++
drivers/block/rnull.rs | 73 ++++++++++++++++++++++++++++++++++++++++++
3 files changed, 85 insertions(+)
create mode 100644 drivers/block/rnull.rs
diff --git a/drivers/block/Kconfig b/drivers/block/Kconfig
index 5b9d4aaebb81d..ed209f4f27983 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 101612cba303a..1105a2d4fdcb0 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 0000000000000..b0227cf9ddd38
--- /dev/null
+++ b/drivers/block/rnull.rs
@@ -0,0 +1,73 @@
+// 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>>>>,
+}
+
+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::new(1, 256, 1), flags::GFP_KERNEL)?;
+
+ let disk = gen_disk::GenDiskBuilder::new()
+ .capacity_sectors(4096 << 11)
+ .logical_block_size(4096)?
+ .physical_block_size(4096)?
+ .rotational(false)
+ .build(format_args!("rnullb{}", 0), tagset)?;
+
+ 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)
+ // We take no refcounts on the request, so we expect to be able to
+ // end the request. The request reference must be unique at this
+ // point, and so `end_ok` cannot fail.
+ .expect("Fatal error - expected to be able to end request");
+
+ Ok(())
+ }
+
+ fn commit_rqs() {}
+}
--
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