[PATCH v2 2/3] rust: block: add rnull, Rust null_blk implementation

Andreas Hindborg
2024-05-21T14:02:02Z

From: Andreas Hindborg <a.hindborg@samsung.com>

This patch adds an initial version of the Rust null block driver.

Signed-off-by: Andreas Hindborg <a.hindborg@samsung.com>
---
drivers/block/Kconfig | 9 +++++
drivers/block/Makefile | 3 ++
drivers/block/rnull.rs | 86 +++++++++++++++++++++++++++++++++++++++++
rust/kernel/block/mq.rs | 4 +-
4 files changed, 101 insertions(+), 1 deletion(-)
create mode 100644 drivers/block/rnull.rs

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..1d6ab6f0f26f
--- /dev/null
+++ b/drivers/block/rnull.rs
@@ -0,0 +1,86 @@
+// 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>>>>,
+}
+
+fn add_disk(tagset: Arc<TagSet<NullBlkDevice>>) -> Result<GenDisk<NullBlkDevice, gen_disk::Added>> {
+ 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::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()
+}
+
+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 = Box::pin_init(
+ new_mutex!(add_disk(tagset)?, "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("Failed to complete request");
+
+ Ok(())
+ }
+
+ fn commit_rqs() {}
+
+ fn complete(rq: ARef<mq::Request<Self>>) {
+ mq::Request::end_ok(rq)
+ .map_err(|_e| kernel::error::code::EIO)
+ .expect("Failed to complete request")
+ }
+}
diff --git a/rust/kernel/block/mq.rs b/rust/kernel/block/mq.rs
index efbd2588791b..54e032bbdffd 100644
--- a/rust/kernel/block/mq.rs
+++ b/rust/kernel/block/mq.rs
@@ -51,6 +51,7 @@
//!
//! ```rust
//! use kernel::{
+//! alloc::flags,
//! block::mq::*,
//! new_mutex,
//! prelude::*,
@@ -77,7 +78,8 @@
//! }
//! }
//!
-//! let tagset: Arc<TagSet<MyBlkDevice>> = Arc::pin_init(TagSet::try_new(1, 256, 1))?;
+//! let tagset: Arc<TagSet<MyBlkDevice>> =
+//! Arc::pin_init(TagSet::try_new(1, 256, 1), flags::GFP_KERNEL)?;
//! let mut disk = gen_disk::try_new(tagset)?;
//! disk.set_name(format_args!("myblk"))?;
//! disk.set_capacity_sectors(4096);
--
2.44.0