Struct Request

pub struct Request<T>(/* private fields */);

A wrapper around a blk-mq struct request. This represents an IO request.

Implementation details

There are four states for a request that the Rust bindings care about:

1. Request is owned by block layer (refcount 0).
2. Request is owned by driver but with zero ARefs in existence (refcount 1).
3. Request is owned by driver with exactly one ARef in existence (refcount 2).
4. Request is owned by driver with more than one ARef in existence (refcount > 2).

We need to track 1 and 2 to ensure we fail tag to request conversions for requests that are not owned by the driver.

We need to track 3 and 4 to ensure that it is safe to end the request and hand back ownership to the block layer.

Note that the driver can still obtain new ARef even if there is no ARefs in existence by using tag_to_rq, hence the need to distinguish B and C.

The states are tracked through the private refcount field of RequestDataWrapper. This structure lives in the private data area of the C struct request.

Invariants

• self.0 is a valid struct request created by the C portion of the kernel.
• The private data area associated with this request must be an initialized and valid RequestDataWrapper<T>.
• self is reference counted by atomic modification of self.wrapper_ref().refcount().

Implementations

impl<T: Operations> Request<T>

pub fn end_ok(this: ARef<Self>) -> Result<(), ARef<Self>>

Notify the block layer that the request has been completed without errors.

This function will return Err if this is not the only ARef referencing the request.

pub fn complete(this: ARef<Self>)

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.

Trait Implementations

impl<T: Operations> AlwaysRefCounted for Request<T>

fn inc_ref(&self)

Increments the reference count on the object.

unsafe fn dec_ref(obj: NonNull<Self>)

Decrements the reference count on the object.

impl<T: Operations> Send for Request<T>

impl<T: Operations> Sync for Request<T>