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Message-Id: <20250616-rnull-up-v6-16-v1-6-a4168b8e76b2@kernel.org>
Date: Mon, 16 Jun 2025 15:23:56 +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 6/9] rust: block: add `GenDisk` private data support
Allow users of the rust block device driver API to install private data in
the `GenDisk` structure.
Signed-off-by: Andreas Hindborg <a.hindborg@...nel.org>
---
drivers/block/rnull/rnull.rs | 8 ++++---
rust/kernel/block/mq.rs | 7 +++---
rust/kernel/block/mq/gen_disk.rs | 46 +++++++++++++++++++++++++++++++-------
rust/kernel/block/mq/operations.rs | 46 ++++++++++++++++++++++++++++++--------
4 files changed, 84 insertions(+), 23 deletions(-)
diff --git a/drivers/block/rnull/rnull.rs b/drivers/block/rnull/rnull.rs
index d09bc77861e4..a012c59ecb3c 100644
--- a/drivers/block/rnull/rnull.rs
+++ b/drivers/block/rnull/rnull.rs
@@ -62,14 +62,16 @@ fn new(
.logical_block_size(block_size)?
.physical_block_size(block_size)?
.rotational(rotational)
- .build(fmt!("{}", name.to_str()?), tagset)
+ .build(fmt!("{}", name.to_str()?), tagset, ())
}
}
#[vtable]
impl Operations for NullBlkDevice {
+ type QueueData = ();
+
#[inline(always)]
- fn queue_rq(rq: ARef<mq::Request<Self>>, _is_last: bool) -> Result {
+ fn queue_rq(_queue_data: (), 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
@@ -80,5 +82,5 @@ fn queue_rq(rq: ARef<mq::Request<Self>>, _is_last: bool) -> Result {
Ok(())
}
- fn commit_rqs() {}
+ fn commit_rqs(_queue_data: ()) {}
}
diff --git a/rust/kernel/block/mq.rs b/rust/kernel/block/mq.rs
index faa3ccb5a49a..34b7425fa94d 100644
--- a/rust/kernel/block/mq.rs
+++ b/rust/kernel/block/mq.rs
@@ -69,20 +69,21 @@
//!
//! #[vtable]
//! impl Operations for MyBlkDevice {
+//! type QueueData = ();
//!
-//! fn queue_rq(rq: ARef<Request<Self>>, _is_last: bool) -> Result {
+//! fn queue_rq(_queue_data: (), rq: ARef<Request<Self>>, _is_last: bool) -> Result {
//! Request::end_ok(rq);
//! Ok(())
//! }
//!
-//! fn commit_rqs() {}
+//! fn commit_rqs(_queue_data: ()) {}
//! }
//!
//! let tagset: Arc<TagSet<MyBlkDevice>> =
//! Arc::pin_init(TagSet::new(1, 256, 1), flags::GFP_KERNEL)?;
//! let mut disk = gen_disk::GenDiskBuilder::new()
//! .capacity_sectors(4096)
-//! .build(format_args!("myblk"), tagset)?;
+//! .build(format_args!("myblk"), tagset, ())?;
//!
//! # Ok::<(), kernel::error::Error>(())
//! ```
diff --git a/rust/kernel/block/mq/gen_disk.rs b/rust/kernel/block/mq/gen_disk.rs
index 34f13e9b286f..3a0fd9e47049 100644
--- a/rust/kernel/block/mq/gen_disk.rs
+++ b/rust/kernel/block/mq/gen_disk.rs
@@ -5,11 +5,18 @@
//! C header: [`include/linux/blkdev.h`](srctree/include/linux/blkdev.h)
//! C header: [`include/linux/blk_mq.h`](srctree/include/linux/blk_mq.h)
-use crate::block::mq::{Operations, TagSet};
-use crate::{bindings, error::from_err_ptr, error::Result, sync::Arc};
-use crate::{error, static_lock_class};
+use crate::{
+ bindings,
+ block::mq::{Operations, TagSet},
+ error::Result,
+ error::{self, from_err_ptr},
+ static_lock_class,
+ str::BufferWriter,
+ sync::Arc,
+ types::ForeignOwnable,
+ types::ScopeGuard,
+};
use core::fmt::{self, Write};
-use kernel::str::BufferWriter;
/// A builder for [`GenDisk`].
///
@@ -93,7 +100,14 @@ pub fn build<T: Operations>(
self,
name: fmt::Arguments<'_>,
tagset: Arc<TagSet<T>>,
+ queue_data: T::QueueData,
) -> Result<GenDisk<T>> {
+ let data = queue_data.into_foreign();
+ let recover_data = ScopeGuard::new(|| {
+ // SAFETY: T::QueueData was created by the call to `into_foreign()` above
+ unsafe { T::QueueData::from_foreign(data) };
+ });
+
// SAFETY: `bindings::queue_limits` contain only fields that are valid when zeroed.
let mut lim: bindings::queue_limits = unsafe { core::mem::zeroed() };
@@ -108,7 +122,7 @@ pub fn build<T: Operations>(
bindings::__blk_mq_alloc_disk(
tagset.raw_tag_set(),
&mut lim,
- core::ptr::null_mut(),
+ data.cast(),
static_lock_class!().as_ptr(),
)
})?;
@@ -162,8 +176,12 @@ pub fn build<T: Operations>(
},
)?;
+ recover_data.dismiss();
+
// INVARIANT: `gendisk` was initialized above.
// INVARIANT: `gendisk` was added to the VFS via `device_add_disk` above.
+ // INVARIANT: `gendisk.queue.queue_data` is set to `data` in the call to
+ // `__blk_mq_alloc_disk` above.
Ok(GenDisk {
_tagset: tagset,
gendisk,
@@ -175,9 +193,10 @@ pub fn build<T: Operations>(
///
/// # Invariants
///
-/// - `gendisk` must always point to an initialized and valid `struct gendisk`.
-/// - `gendisk` was added to the VFS through a call to
-/// `bindings::device_add_disk`.
+/// - `gendisk` must always point to an initialized and valid `struct gendisk`.
+/// - `gendisk` was added to the VFS through a call to
+/// `bindings::device_add_disk`.
+/// - `self.gendisk.queue.queuedata` is initialized by a call to `ForeignOwnable::into_foreign`.
pub struct GenDisk<T: Operations> {
_tagset: Arc<TagSet<T>>,
gendisk: *mut bindings::gendisk,
@@ -189,9 +208,20 @@ unsafe impl<T: Operations + Send> Send for GenDisk<T> {}
impl<T: Operations> Drop for GenDisk<T> {
fn drop(&mut self) {
+ // SAFETY: By type invariant of `Self`, `self.gendisk` points to a valid
+ // and initialized instance of `struct gendisk`, and, `queuedata` was
+ // initialized with the result of a call to
+ // `ForeignOwnable::into_foreign`.
+ let queue_data = unsafe { (*(*self.gendisk).queue).queuedata };
+
// SAFETY: By type invariant, `self.gendisk` points to a valid and
// initialized instance of `struct gendisk`, and it was previously added
// to the VFS.
unsafe { bindings::del_gendisk(self.gendisk) };
+
+ // SAFETY: `queue.queuedata` was created by `GenDiskBuilder::build` with
+ // a call to `ForeignOwnable::into_foreign` to create `queuedata`.
+ // `ForeignOwnable::from_foreign` is only called here.
+ let _queue_data = unsafe { T::QueueData::from_foreign(queue_data.cast()) };
}
}
diff --git a/rust/kernel/block/mq/operations.rs b/rust/kernel/block/mq/operations.rs
index 864ff379dc91..c50959d5517b 100644
--- a/rust/kernel/block/mq/operations.rs
+++ b/rust/kernel/block/mq/operations.rs
@@ -6,14 +6,15 @@
use crate::{
bindings,
- block::mq::request::RequestDataWrapper,
- block::mq::Request,
+ block::mq::{request::RequestDataWrapper, Request},
error::{from_result, Result},
prelude::*,
- types::ARef,
+ types::{ARef, ForeignOwnable},
};
use core::{marker::PhantomData, sync::atomic::AtomicU64, sync::atomic::Ordering};
+type ForeignBorrowed<'a, T> = <T as ForeignOwnable>::Borrowed<'a>;
+
/// Implement this trait to interface blk-mq as block devices.
///
/// To implement a block device driver, implement this trait as described in the
@@ -26,12 +27,20 @@
/// [module level documentation]: kernel::block::mq
#[macros::vtable]
pub trait Operations: Sized {
+ /// Data associated with the `struct request_queue` that is allocated for
+ /// the `GenDisk` associated with this `Operations` implementation.
+ type QueueData: ForeignOwnable;
+
/// Called by the kernel to queue a request with the driver. If `is_last` is
/// `false`, the driver is allowed to defer committing the request.
- fn queue_rq(rq: ARef<Request<Self>>, is_last: bool) -> Result;
+ fn queue_rq(
+ queue_data: ForeignBorrowed<'_, Self::QueueData>,
+ rq: ARef<Request<Self>>,
+ is_last: bool,
+ ) -> Result;
/// Called by the kernel to indicate that queued requests should be submitted.
- fn commit_rqs();
+ fn commit_rqs(queue_data: ForeignBorrowed<'_, Self::QueueData>);
/// Called by the kernel to poll the device for completed requests. Only
/// used for poll queues.
@@ -70,7 +79,7 @@ impl<T: Operations> OperationsVTable<T> {
/// promise to not access the request until the driver calls
/// `bindings::blk_mq_end_request` for the request.
unsafe extern "C" fn queue_rq_callback(
- _hctx: *mut bindings::blk_mq_hw_ctx,
+ hctx: *mut bindings::blk_mq_hw_ctx,
bd: *const bindings::blk_mq_queue_data,
) -> bindings::blk_status_t {
// SAFETY: `bd.rq` is valid as required by the safety requirement for
@@ -88,10 +97,20 @@ impl<T: Operations> OperationsVTable<T> {
// reference counted by `ARef` until then.
let rq = unsafe { Request::aref_from_raw((*bd).rq) };
+ // SAFETY: `hctx` is valid as required by this function.
+ let queue_data = unsafe { (*(*hctx).queue).queuedata };
+
+ // SAFETY: `queue.queuedata` was created by `GenDisk::try_new()` with a
+ // call to `ForeignOwnable::into_pointer()` to create `queuedata`.
+ // `ForeignOwnable::from_foreign()` is only called when the tagset is
+ // dropped, which happens after we are dropped.
+ let queue_data = unsafe { T::QueueData::borrow(queue_data.cast()) };
+
// SAFETY: We have exclusive access and we just set the refcount above.
unsafe { Request::start_unchecked(&rq) };
let ret = T::queue_rq(
+ queue_data,
rq,
// SAFETY: `bd` is valid as required by the safety requirement for
// this function.
@@ -110,9 +129,18 @@ impl<T: Operations> OperationsVTable<T> {
///
/// # Safety
///
- /// This function may only be called by blk-mq C infrastructure.
- unsafe extern "C" fn commit_rqs_callback(_hctx: *mut bindings::blk_mq_hw_ctx) {
- T::commit_rqs()
+ /// This function may only be called by blk-mq C infrastructure. The caller
+ /// must ensure that `hctx` is valid.
+ unsafe extern "C" fn commit_rqs_callback(hctx: *mut bindings::blk_mq_hw_ctx) {
+ // SAFETY: `hctx` is valid as required by this function.
+ let queue_data = unsafe { (*(*hctx).queue).queuedata };
+
+ // SAFETY: `queue.queuedata` was created by `GenDisk::try_new()` with a
+ // call to `ForeignOwnable::into_pointer()` to create `queuedata`.
+ // `ForeignOwnable::from_foreign()` is only called when the tagset is
+ // dropped, which happens after we are dropped.
+ let queue_data = unsafe { T::QueueData::borrow(queue_data.cast()) };
+ T::commit_rqs(queue_data)
}
/// This function is called by the C kernel. It is not currently
--
2.47.2
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