blk_queue_end_tag -- end tag operations for a request
void blk_queue_end_tag (request_queue_t * q, struct request * rq);
the request queue for the device
the request that has completed
Typically called when end_that_request_first returns 0, meaning
all transfers have been done for a request. It's important to call
this function before end_that_request_last, as that will put the
request back on the free list thus corrupting the internal tag list.
queue lock must be held.