Struct Request

pub struct Request<T: Operations>(/* 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.

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.

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>