From 119e9db233ad0f4cbd4cfb9f9385a7bca378b37d Mon Sep 17 00:00:00 2001 From: Zeng Chi Date: Mon, 21 Sep 2026 18:24:42 +0800 Subject: KVM: Don't pre-reserve xarray entries when storing empty/NULL attributes Skip the xarray reservation loop when clearing all memory attributes, as storing NULL only erases the entry and never needs to allocate, so no reservation (and no cleanup of a failed one) is required in that case. Suggested-by: Sean Christopherson Cc: David Ballesteros Signed-off-by: Zeng Chi Link: https://patch.msgid.link/20260921102442.1232375-1-zeng_chi911@163.com [sean: split to separate patch] Signed-off-by: Sean Christopherson --- drivers/block/rnull/Kconfig | 13 ++ drivers/block/rnull/Makefile | 3 + drivers/block/rnull/configfs.rs | 261 ++++++++++++++++++++++++++++++++++++++++ drivers/block/rnull/rnull.rs | 100 +++++++++++++++ 4 files changed, 377 insertions(+) create mode 100644 drivers/block/rnull/Kconfig create mode 100644 drivers/block/rnull/Makefile create mode 100644 drivers/block/rnull/configfs.rs create mode 100644 drivers/block/rnull/rnull.rs (limited to 'drivers/block/rnull') diff --git a/drivers/block/rnull/Kconfig b/drivers/block/rnull/Kconfig new file mode 100644 index 000000000..7bc5b376c --- /dev/null +++ b/drivers/block/rnull/Kconfig @@ -0,0 +1,13 @@ +# SPDX-License-Identifier: GPL-2.0 +# +# Rust null block device driver configuration + +config BLK_DEV_RUST_NULL + tristate "Rust null block driver (Experimental)" + 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 + devices that can be configured via various configuration options. + + If unsure, say N. diff --git a/drivers/block/rnull/Makefile b/drivers/block/rnull/Makefile new file mode 100644 index 000000000..11cfa5e61 --- /dev/null +++ b/drivers/block/rnull/Makefile @@ -0,0 +1,3 @@ + +obj-$(CONFIG_BLK_DEV_RUST_NULL) += rnull_mod.o +rnull_mod-y := rnull.o diff --git a/drivers/block/rnull/configfs.rs b/drivers/block/rnull/configfs.rs new file mode 100644 index 000000000..32c10c3f4 --- /dev/null +++ b/drivers/block/rnull/configfs.rs @@ -0,0 +1,261 @@ +// SPDX-License-Identifier: GPL-2.0 + +use super::NullBlkDevice; +use kernel::{ + block::mq::gen_disk::{GenDisk, GenDiskBuilder}, + configfs::{self, AttributeOperations}, + configfs_attrs, + fmt::{self, Write as _}, + new_mutex, + page::PAGE_SIZE, + prelude::*, + str::{kstrtobool_bytes, CString}, + sync::Mutex, +}; + +pub(crate) fn subsystem() -> impl PinInit, Error> { + let item_type = configfs_attrs! { + container: configfs::Subsystem, + data: Config, + child: DeviceConfig, + attributes: [ + features: 0, + ], + }; + + kernel::configfs::Subsystem::new(c"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 { + let mut writer = kernel::str::Formatter::new(page); + writer.write_str("blocksize,size,rotational,irqmode\n")?; + Ok(writer.bytes_written()) + } +} + +#[vtable] +impl configfs::GroupOperations for Config { + type Child = DeviceConfig; + + fn make_group( + &self, + name: &CStr, + ) -> Result, Error>> { + let item_type = configfs_attrs! { + container: configfs::Group, + data: DeviceConfig, + attributes: [ + // Named for compatibility with C null_blk + power: 0, + blocksize: 1, + rotational: 2, + size: 3, + irqmode: 4, + ], + }; + + 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, + irq_mode: IRQMode::None, + name: name.try_into()?, + }), + }), + )) + } +} + +#[derive(Debug, Clone, Copy)] +pub(crate) enum IRQMode { + None, + Soft, +} + +impl TryFrom for IRQMode { + type Error = kernel::error::Error; + + fn try_from(value: u8) -> Result { + match value { + 0 => Ok(Self::None), + 1 => Ok(Self::Soft), + _ => Err(EINVAL), + } + } +} + +impl fmt::Display for IRQMode { + fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { + match self { + Self::None => f.write_str("0")?, + Self::Soft => f.write_str("1")?, + } + Ok(()) + } +} + +#[pin_data] +pub(crate) struct DeviceConfig { + #[pin] + data: Mutex, +} + +#[pin_data] +struct DeviceConfigInner { + powered: bool, + name: CString, + block_size: u32, + rotational: bool, + capacity_mib: u64, + irq_mode: IRQMode, + disk: Option>, +} + +#[vtable] +impl configfs::AttributeOperations<0> for DeviceConfig { + type Data = DeviceConfig; + + fn show(this: &DeviceConfig, page: &mut [u8; PAGE_SIZE]) -> Result { + let mut writer = kernel::str::Formatter::new(page); + + if this.data.lock().powered { + writer.write_str("1\n")?; + } else { + writer.write_str("0\n")?; + } + + Ok(writer.bytes_written()) + } + + fn store(this: &DeviceConfig, page: &[u8]) -> Result { + let power_op = kstrtobool_bytes(page)?; + 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.irq_mode, + )?); + 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 { + let mut writer = kernel::str::Formatter::new(page); + writer.write_fmt(fmt!("{}\n", this.data.lock().block_size))?; + Ok(writer.bytes_written()) + } + + 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::().map_err(|_| 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 { + let mut writer = kernel::str::Formatter::new(page); + + if this.data.lock().rotational { + writer.write_str("1\n")?; + } else { + writer.write_str("0\n")?; + } + + Ok(writer.bytes_written()) + } + + fn store(this: &DeviceConfig, page: &[u8]) -> Result { + if this.data.lock().powered { + return Err(EBUSY); + } + + this.data.lock().rotational = kstrtobool_bytes(page)?; + + Ok(()) + } +} + +#[vtable] +impl configfs::AttributeOperations<3> for DeviceConfig { + type Data = DeviceConfig; + + fn show(this: &DeviceConfig, page: &mut [u8; PAGE_SIZE]) -> Result { + let mut writer = kernel::str::Formatter::new(page); + writer.write_fmt(fmt!("{}\n", this.data.lock().capacity_mib))?; + Ok(writer.bytes_written()) + } + + 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::().map_err(|_| EINVAL)?; + + this.data.lock().capacity_mib = value; + Ok(()) + } +} + +#[vtable] +impl configfs::AttributeOperations<4> for DeviceConfig { + type Data = DeviceConfig; + + fn show(this: &DeviceConfig, page: &mut [u8; PAGE_SIZE]) -> Result { + let mut writer = kernel::str::Formatter::new(page); + writer.write_fmt(fmt!("{}\n", this.data.lock().irq_mode))?; + Ok(writer.bytes_written()) + } + + 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::().map_err(|_| EINVAL)?; + + this.data.lock().irq_mode = IRQMode::try_from(value)?; + Ok(()) + } +} diff --git a/drivers/block/rnull/rnull.rs b/drivers/block/rnull/rnull.rs new file mode 100644 index 000000000..0ca8715fe --- /dev/null +++ b/drivers/block/rnull/rnull.rs @@ -0,0 +1,100 @@ +// SPDX-License-Identifier: GPL-2.0 + +//! This is a Rust implementation of the C null block driver. + +mod configfs; + +use configfs::IRQMode; +use kernel::{ + block::{ + self, + mq::{ + self, + gen_disk::{self, GenDisk}, + Operations, TagSet, + }, + }, + prelude::*, + sync::{aref::ARef, Arc}, +}; + +module! { + type: NullBlkModule, + name: "rnull_mod", + authors: ["Andreas Hindborg"], + description: "Rust implementation of the C null block driver", + license: "GPL v2", +} + +#[pin_data] +struct NullBlkModule { + #[pin] + configfs_subsystem: kernel::configfs::Subsystem, +} + +impl kernel::InPlaceModule for NullBlkModule { + fn init(_module: &'static ThisModule) -> impl PinInit { + pr_info!("Rust null_blk loaded\n"); + + try_pin_init!(Self { + configfs_subsystem <- configfs::subsystem(), + }) + } +} + +struct NullBlkDevice; + +impl NullBlkDevice { + fn new( + name: &CStr, + block_size: u32, + rotational: bool, + capacity_mib: u64, + irq_mode: IRQMode, + ) -> Result> { + let tagset = Arc::pin_init(TagSet::new(1, 256, 1), GFP_KERNEL)?; + + let queue_data = Box::new(QueueData { irq_mode }, 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, queue_data) + } +} + +struct QueueData { + irq_mode: IRQMode, +} + +#[vtable] +impl Operations for NullBlkDevice { + type QueueData = KBox; + + #[inline(always)] + fn queue_rq(queue_data: &QueueData, rq: ARef>, _is_last: bool) -> Result { + match queue_data.irq_mode { + IRQMode::None => 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"), + IRQMode::Soft => mq::Request::complete(rq), + } + Ok(()) + } + + fn commit_rqs(_queue_data: &QueueData) {} + + fn complete(rq: ARef>) { + 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"); + } +} -- cgit v1.3.1