Commit 4ec05284 authored by Andreas Hindborg's avatar Andreas Hindborg Committed by Jens Axboe
Browse files

rust: block: add remote completion to `Request` 



Allow users of rust block device driver API to schedule completion of
requests via `blk_mq_complete_request_remote`.

Reviewed-by: default avatarAlice Ryhl <aliceryhl@google.com>
Reviewed-by: default avatarDaniel Almeida <daniel.almeida@collabora.com>
Signed-off-by: default avatarAndreas Hindborg <a.hindborg@kernel.org>
Link: https://lore.kernel.org/r/20250902-rnull-up-v6-16-v7-16-b5212cc89b98@kernel.org


Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent bde50e28

drivers/block/rnull/rnull.rs

+9 −0
Original line number Diff line number Diff line
@@ -82,4 +82,13 @@ fn queue_rq(_queue_data: (), rq: ARef<mq::Request<Self>>, _is_last: bool) -> Res 
    }



    fn commit_rqs(_queue_data: ()) {}



    fn complete(rq: ARef<mq::Request<Self>>) {

        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");

    }

}

rust/kernel/block/mq.rs

+6 −0
Original line number Diff line number Diff line
@@ -77,6 +77,12 @@ 
//!     }

//!

//!     fn commit_rqs(_queue_data: ()) {}

//!

//!     fn complete(rq: ARef<Request<Self>>) {

//!         Request::end_ok(rq)

//!             .map_err(|_e| kernel::error::code::EIO)

//!             .expect("Fatal error - expected to be able to end request");

//!     }

//! }

//!

//! let tagset: Arc<TagSet<MyBlkDevice>> =

rust/kernel/block/mq/operations.rs

+15 −4
Original line number Diff line number Diff line
@@ -42,6 +42,9 @@ fn queue_rq( 
    /// Called by the kernel to indicate that queued requests should be submitted.

    fn commit_rqs(queue_data: ForeignBorrowed<'_, Self::QueueData>);



    /// Called by the kernel when the request is completed.

    fn complete(rq: ARef<Request<Self>>);



    /// Called by the kernel to poll the device for completed requests. Only

    /// used for poll queues.

    fn poll() -> bool {
@@ -143,13 +146,21 @@ impl<T: Operations> OperationsVTable<T> { 
        T::commit_rqs(queue_data)

    }



    /// This function is called by the C kernel. It is not currently

    /// implemented, and there is no way to exercise this code path.

    /// This function is called by the C kernel. A pointer to this function is

    /// installed in the `blk_mq_ops` vtable for the driver.

    ///

    /// # Safety

    ///

    /// This function may only be called by blk-mq C infrastructure.

    unsafe extern "C" fn complete_callback(_rq: *mut bindings::request) {}

    /// This function may only be called by blk-mq C infrastructure. `rq` must

    /// point to a valid request that has been marked as completed. The pointee

    /// of `rq` must be valid for write for the duration of this function.

    unsafe extern "C" fn complete_callback(rq: *mut bindings::request) {

        // SAFETY: This function can only be dispatched through

        // `Request::complete`. We leaked a refcount then which we pick back up

        // now.

        let aref = unsafe { Request::aref_from_raw(rq) };

        T::complete(aref);

    }



    /// This function is called by the C kernel. A pointer to this function is

    /// installed in the `blk_mq_ops` vtable for the driver.

rust/kernel/block/mq/request.rs

+17 −0
Original line number Diff line number Diff line
@@ -135,6 +135,23 @@ pub fn end_ok(this: ARef<Self>) -> Result<(), ARef<Self>> { 
        Ok(())

    }



    /// Complete the request by scheduling `Operations::complete` for

    /// execution.

    ///

    /// The function may be scheduled locally, via SoftIRQ or remotely via IPMI.

    /// See `blk_mq_complete_request_remote` in [`blk-mq.c`] for details.

    ///

    /// [`blk-mq.c`]: srctree/block/blk-mq.c

    pub fn complete(this: ARef<Self>) {

        let ptr = ARef::into_raw(this).cast::<bindings::request>().as_ptr();

        // SAFETY: By type invariant, `self.0` is a valid `struct request`

        if !unsafe { bindings::blk_mq_complete_request_remote(ptr) } {

            // SAFETY: We released a refcount above that we can reclaim here.

            let this = unsafe { Request::aref_from_raw(ptr) };

            T::complete(this);

        }

    }



    /// Return a pointer to the [`RequestDataWrapper`] stored in the private area

    /// of the request structure.

    ///