block: remove deadline __deadline manipulation helpers

No users left since the removal of the legacy request interface, we can
remove all the magic bit stealing now and make it a normal field.

But use WRITE_ONCE/READ_ONCE on the new deadline field, given that we
don't seem to have any mechanism to guarantee a new value actually
gets seen by other threads.

Reviewed-by: Hannes Reinecke <hare@suse.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
diff --git a/block/blk-mq.c b/block/blk-mq.c
index 411be60..4c82b4b 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -325,7 +325,7 @@ static struct request *blk_mq_rq_ctx_init(struct blk_mq_alloc_data *data,
 	rq->special = NULL;
 	/* tag was already set */
 	rq->extra_len = 0;
-	rq->__deadline = 0;
+	WRITE_ONCE(rq->deadline, 0);
 
 	rq->timeout = 0;
 
@@ -839,7 +839,7 @@ static bool blk_mq_req_expired(struct request *rq, unsigned long *next)
 	if (rq->rq_flags & RQF_TIMED_OUT)
 		return false;
 
-	deadline = blk_rq_deadline(rq);
+	deadline = READ_ONCE(rq->deadline);
 	if (time_after_eq(jiffies, deadline))
 		return true;