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Message-Id: <20250616-rnull-up-v6-16-v1-5-a4168b8e76b2@kernel.org>
Date: Mon, 16 Jun 2025 15:23:55 +0200
From: Andreas Hindborg <a.hindborg@...nel.org>
To: Boqun Feng <boqun.feng@...il.com>, Miguel Ojeda <ojeda@...nel.org>,
Alex Gaynor <alex.gaynor@...il.com>, Gary Guo <gary@...yguo.net>,
Björn Roy Baron <bjorn3_gh@...tonmail.com>,
Benno Lossin <lossin@...nel.org>, Alice Ryhl <aliceryhl@...gle.com>,
Trevor Gross <tmgross@...ch.edu>, Danilo Krummrich <dakr@...nel.org>,
Jens Axboe <axboe@...nel.dk>
Cc: linux-block@...r.kernel.org, rust-for-linux@...r.kernel.org,
linux-kernel@...r.kernel.org, Andreas Hindborg <a.hindborg@...nel.org>
Subject: [PATCH 5/9] rnull: enable configuration via `configfs`
Allow rust null block devices to be configured and instantiated via
`configfs`.
Signed-off-by: Andreas Hindborg <a.hindborg@...nel.org>
---
drivers/block/rnull/Kconfig | 2 +-
drivers/block/rnull/configfs.rs | 220 +++++++++++++++++++++++++++++++++++++++
drivers/block/rnull/rnull.rs | 58 ++++++-----
rust/kernel/block/mq/gen_disk.rs | 2 +-
4 files changed, 253 insertions(+), 29 deletions(-)
diff --git a/drivers/block/rnull/Kconfig b/drivers/block/rnull/Kconfig
index 6dc5aff96bf4..7bc5b376c128 100644
--- a/drivers/block/rnull/Kconfig
+++ b/drivers/block/rnull/Kconfig
@@ -4,7 +4,7 @@
config BLK_DEV_RUST_NULL
tristate "Rust null block driver (Experimental)"
- depends on RUST
+ depends on RUST && CONFIGFS_FS
help
This is the Rust implementation of the null block driver. Like
the C version, the driver allows the user to create virutal block
diff --git a/drivers/block/rnull/configfs.rs b/drivers/block/rnull/configfs.rs
new file mode 100644
index 000000000000..315e04fbf14f
--- /dev/null
+++ b/drivers/block/rnull/configfs.rs
@@ -0,0 +1,220 @@
+// SPDX-License-Identifier: GPL-2.0
+
+use super::{NullBlkDevice, THIS_MODULE};
+use core::fmt::Write;
+use kernel::{
+ block::mq::gen_disk::{GenDisk, GenDiskBuilder},
+ c_str,
+ configfs::{self, AttributeOperations},
+ configfs_attrs, new_mutex,
+ page::PAGE_SIZE,
+ prelude::*,
+ str::CString,
+ sync::Mutex,
+};
+use pin_init::PinInit;
+
+pub(crate) fn subsystem() -> impl PinInit<kernel::configfs::Subsystem<Config>, Error> {
+ let item_type = configfs_attrs! {
+ container: configfs::Subsystem<Config>,
+ data: Config,
+ child: DeviceConfig,
+ attributes: [
+ features: 0,
+ ],
+ };
+
+ kernel::configfs::Subsystem::new(c_str!("rnull"), item_type, try_pin_init!(Config {}))
+}
+
+#[pin_data]
+pub(crate) struct Config {}
+
+#[vtable]
+impl AttributeOperations<0> for Config {
+ type Data = Config;
+
+ fn show(_this: &Config, page: &mut [u8; PAGE_SIZE]) -> Result<usize> {
+ let mut writer = kernel::str::BufferWriter::new(page)?;
+ writer.write_str("blocksize,size,rotational\n")?;
+ Ok(writer.pos())
+ }
+}
+
+#[vtable]
+impl configfs::GroupOperations for Config {
+ type Child = DeviceConfig;
+
+ fn make_group(
+ &self,
+ name: &CStr,
+ ) -> Result<impl PinInit<configfs::Group<DeviceConfig>, Error>> {
+ let item_type = configfs_attrs! {
+ container: configfs::Group<DeviceConfig>,
+ data: DeviceConfig,
+ attributes: [
+ // Named for compatibility with C null_blk
+ power: 0,
+ blocksize: 1,
+ rotational: 2,
+ size: 3,
+ ],
+ };
+
+ Ok(configfs::Group::new(
+ name.try_into()?,
+ item_type,
+ // TODO: cannot coerce new_mutex!() to impl PinInit<_, Error>, so put mutex inside
+ try_pin_init!( DeviceConfig {
+ data <- new_mutex!( DeviceConfigInner {
+ powered: false,
+ block_size: 4096,
+ rotational: false,
+ disk: None,
+ capacity_mib: 4096,
+ name: name.try_into()?,
+ }),
+ }),
+ ))
+ }
+}
+
+#[pin_data]
+pub(crate) struct DeviceConfig {
+ #[pin]
+ data: Mutex<DeviceConfigInner>,
+}
+
+#[pin_data]
+struct DeviceConfigInner {
+ powered: bool,
+ name: CString,
+ block_size: u32,
+ rotational: bool,
+ capacity_mib: u64,
+ disk: Option<GenDisk<NullBlkDevice>>,
+}
+
+#[vtable]
+impl configfs::AttributeOperations<0> for DeviceConfig {
+ type Data = DeviceConfig;
+
+ fn show(this: &DeviceConfig, page: &mut [u8; PAGE_SIZE]) -> Result<usize> {
+ let mut writer = kernel::str::BufferWriter::new(page)?;
+
+ if this.data.lock().powered {
+ writer.write_fmt(fmt!("1\n"))?;
+ } else {
+ writer.write_fmt(fmt!("0\n"))?;
+ }
+
+ Ok(writer.pos())
+ }
+
+ fn store(this: &DeviceConfig, page: &[u8]) -> Result {
+ let power_op: bool = core::str::from_utf8(page)?
+ .trim()
+ .parse::<u8>()
+ .map_err(|_| kernel::error::code::EINVAL)?
+ != 0;
+
+ let mut guard = this.data.lock();
+
+ if !guard.powered && power_op {
+ guard.disk = Some(NullBlkDevice::new(
+ &guard.name,
+ guard.block_size,
+ guard.rotational,
+ guard.capacity_mib,
+ )?);
+ guard.powered = true;
+ } else if guard.powered && !power_op {
+ drop(guard.disk.take());
+ guard.powered = false;
+ }
+
+ Ok(())
+ }
+}
+
+#[vtable]
+impl configfs::AttributeOperations<1> for DeviceConfig {
+ type Data = DeviceConfig;
+
+ fn show(this: &DeviceConfig, page: &mut [u8; PAGE_SIZE]) -> Result<usize> {
+ let mut writer = kernel::str::BufferWriter::new(page)?;
+ writer.write_fmt(fmt!("{}\n", this.data.lock().block_size))?;
+ Ok(writer.pos())
+ }
+
+ fn store(this: &DeviceConfig, page: &[u8]) -> Result {
+ if this.data.lock().powered {
+ return Err(EBUSY);
+ }
+
+ let text = core::str::from_utf8(page)?.trim();
+ let value = text
+ .parse::<u32>()
+ .map_err(|_| kernel::error::code::EINVAL)?;
+
+ GenDiskBuilder::validate_block_size(value)?;
+ this.data.lock().block_size = value;
+ Ok(())
+ }
+}
+
+#[vtable]
+impl configfs::AttributeOperations<2> for DeviceConfig {
+ type Data = DeviceConfig;
+
+ fn show(this: &DeviceConfig, page: &mut [u8; PAGE_SIZE]) -> Result<usize> {
+ let mut writer = kernel::str::BufferWriter::new(page)?;
+
+ if this.data.lock().rotational {
+ writer.write_fmt(fmt!("1\n"))?;
+ } else {
+ writer.write_fmt(fmt!("0\n"))?;
+ }
+
+ Ok(writer.pos())
+ }
+
+ fn store(this: &DeviceConfig, page: &[u8]) -> Result {
+ if this.data.lock().powered {
+ return Err(EBUSY);
+ }
+
+ this.data.lock().rotational = core::str::from_utf8(page)?
+ .trim()
+ .parse::<u8>()
+ .map_err(|_| kernel::error::code::EINVAL)?
+ != 0;
+
+ Ok(())
+ }
+}
+
+#[vtable]
+impl configfs::AttributeOperations<3> for DeviceConfig {
+ type Data = DeviceConfig;
+
+ fn show(this: &DeviceConfig, page: &mut [u8; PAGE_SIZE]) -> Result<usize> {
+ let mut writer = kernel::str::BufferWriter::new(page)?;
+ writer.write_fmt(fmt!("{}\n", this.data.lock().capacity_mib))?;
+ Ok(writer.pos())
+ }
+
+ fn store(this: &DeviceConfig, page: &[u8]) -> Result {
+ if this.data.lock().powered {
+ return Err(EBUSY);
+ }
+
+ let text = core::str::from_utf8(page)?.trim();
+ let value = text
+ .parse::<u64>()
+ .map_err(|_| kernel::error::code::EINVAL)?;
+
+ this.data.lock().capacity_mib = value;
+ Ok(())
+ }
+}
diff --git a/drivers/block/rnull/rnull.rs b/drivers/block/rnull/rnull.rs
index d07e76ae2c13..d09bc77861e4 100644
--- a/drivers/block/rnull/rnull.rs
+++ b/drivers/block/rnull/rnull.rs
@@ -1,28 +1,26 @@
// 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.
+
+mod configfs;
use kernel::{
alloc::flags,
- block::mq::{
+ block::{
self,
- gen_disk::{self, GenDisk},
- Operations, TagSet,
+ mq::{
+ self,
+ gen_disk::{self, GenDisk},
+ Operations, TagSet,
+ },
},
error::Result,
- new_mutex, pr_info,
+ pr_info,
prelude::*,
- sync::{Arc, Mutex},
+ sync::Arc,
types::ARef,
};
+use pin_init::PinInit;
module! {
type: NullBlkModule,
@@ -35,33 +33,39 @@
#[pin_data]
struct NullBlkModule {
#[pin]
- _disk: Mutex<GenDisk<NullBlkDevice>>,
+ configfs_subsystem: kernel::configfs::Subsystem<configfs::Config>,
}
impl kernel::InPlaceModule for NullBlkModule {
fn init(_module: &'static ThisModule) -> impl PinInit<Self, Error> {
pr_info!("Rust null_blk loaded\n");
- // Use a immediately-called closure as a stable `try` block
- let disk = /* try */ (|| {
- let tagset = Arc::pin_init(TagSet::new(1, 256, 1), flags::GFP_KERNEL)?;
-
- gen_disk::GenDiskBuilder::new()
- .capacity_sectors(4096 << 11)
- .logical_block_size(4096)?
- .physical_block_size(4096)?
- .rotational(false)
- .build(format_args!("rnullb{}", 0), tagset)
- })();
-
try_pin_init!(Self {
- _disk <- new_mutex!(disk?, "nullb:disk"),
+ configfs_subsystem <- configfs::subsystem(),
})
}
}
struct NullBlkDevice;
+impl NullBlkDevice {
+ fn new(
+ name: &CStr,
+ block_size: u32,
+ rotational: bool,
+ capacity_mib: u64,
+ ) -> Result<GenDisk<Self>> {
+ let tagset = Arc::pin_init(TagSet::new(1, 256, 1), flags::GFP_KERNEL)?;
+
+ gen_disk::GenDiskBuilder::new()
+ .capacity_sectors(capacity_mib << (20 - block::SECTOR_SHIFT))
+ .logical_block_size(block_size)?
+ .physical_block_size(block_size)?
+ .rotational(rotational)
+ .build(fmt!("{}", name.to_str()?), tagset)
+ }
+}
+
#[vtable]
impl Operations for NullBlkDevice {
#[inline(always)]
diff --git a/rust/kernel/block/mq/gen_disk.rs b/rust/kernel/block/mq/gen_disk.rs
index a04b709514ac..34f13e9b286f 100644
--- a/rust/kernel/block/mq/gen_disk.rs
+++ b/rust/kernel/block/mq/gen_disk.rs
@@ -46,7 +46,7 @@ pub fn rotational(mut self, rotational: bool) -> Self {
/// Validate block size by verifying that it is between 512 and `PAGE_SIZE`,
/// and that it is a power of two.
- fn validate_block_size(size: u32) -> Result {
+ pub fn validate_block_size(size: u32) -> Result {
if !(512..=bindings::PAGE_SIZE as u32).contains(&size) || !size.is_power_of_two() {
Err(error::code::EINVAL)
} else {
--
2.47.2
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