Provided by: linux-doc-2.6.15_2.6.15-23.39_all
blk_insert_request - insert a special request in to a request queue
void blk_insert_request (request_queue_t * q, struct request * rq,
int at_head, void * data);
q request queue where request should be inserted
rq request to be inserted
insert request at head or tail of queue
data private data
Many block devices need to execute commands asynchronously, so they
don’t block the whole kernel from preemption during request execution.
This is accomplished normally by inserting aritficial requests tagged
as REQ_SPECIAL in to the corresponding request queue, and letting them
be scheduled for actual execution by the request queue.
We have the option of inserting the head or the tail of the queue.
Typically we use the tail for new ioctls and so forth. We use the head
of the queue for things like a QUEUE_FULL message from a device, or a
host that is unable to accept a particular command.