blk_queue_unprep_rq (9) - Linux Man Pages
blk_queue_unprep_rq: set an unprepare_request function for queue
blk_queue_unprep_rq - set an unprepare_request function for queue
void blk_queue_unprep_rq(struct request_queue
*q, unprep_rq_fn *ufn);
- unprepare_request function
It's possible for a queue to register an unprepare_request callback which is invoked before the request is finally completed. The goal of the function is to deallocate any data that was allocated in the prepare_request callback.