block: cache rq_flags inside blk_mq_rq_ctx_init()

Add a local variable for rq_flags, it helps to compile out some of
rq_flags reloads.
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

block/blk-mq.c

@@ -318,17 +318,23 @@ static struct request *blk_mq_rq_ctx_init(struct blk_mq_alloc_data *data,
 	struct elevator_queue *e = q->elevator;
 	struct blk_mq_tags *tags = blk_mq_tags_from_data(data);
 	struct request *rq = tags->static_rqs[tag];
+	unsigned int rq_flags = 0;
 
 	if (e) {
-		rq->rq_flags = RQF_ELV;
+		rq_flags = RQF_ELV;
 		rq->tag = BLK_MQ_NO_TAG;
 		rq->internal_tag = tag;
 	} else {
-		rq->rq_flags = 0;
 		rq->tag = tag;
 		rq->internal_tag = BLK_MQ_NO_TAG;
 	}
 
+	if (data->flags & BLK_MQ_REQ_PM)
+		rq_flags |= RQF_PM;
+	if (blk_queue_io_stat(q))
+		rq_flags |= RQF_IO_STAT;
+	rq->rq_flags = rq_flags;
+
 	if (blk_mq_need_time_stamp(rq))
 		rq->start_time_ns = ktime_get_ns();
 	else
@@ -338,10 +344,6 @@ static struct request *blk_mq_rq_ctx_init(struct blk_mq_alloc_data *data,
 	rq->mq_ctx = ctx;
 	rq->mq_hctx = hctx;
 	rq->cmd_flags = data->cmd_flags;
-	if (data->flags & BLK_MQ_REQ_PM)
-		rq->rq_flags |= RQF_PM;
-	if (blk_queue_io_stat(q))
-		rq->rq_flags |= RQF_IO_STAT;
 	rq->rq_disk = NULL;
 	rq->part = NULL;
 #ifdef CONFIG_BLK_RQ_ALLOC_TIME