blk_old_get_request already has it at hand, and in blk_queue_bio, which
is the fast path, it is constant.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NHannes Reinecke <hare@suse.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>