blk-mq: cleanup shared tags case in blk_mq_update_nr_requests()

For shared tags case, all hctx->sched_tags/tags are the same, it doesn't
make sense to call into blk_mq_tag_update_depth() multiple times for the
same tags.

Signed-off-by: Yu Kuai <yukuai3@huawei.com>
Reviewed-by: Nilay Shroff <nilay@linux.ibm.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

Author: YuKuai-huawei

block/blk-mq-tag.c

@@ -622,13 +622,6 @@ int blk_mq_tag_update_depth(struct blk_mq_hw_ctx *hctx,
 		struct blk_mq_tag_set *set = hctx->queue->tag_set;
 		struct blk_mq_tags *new;
 
-		/*
-		 * Only the sbitmap needs resizing since we allocated the max
-		 * initially.
-		 */
-		if (blk_mq_is_shared_tags(set->flags))
-			return 0;
-
 		new = blk_mq_alloc_map_and_rqs(set, hctx->queue_num, tdepth);
 		if (!new)
 			return -ENOMEM;

block/blk-mq.c

@@ -4935,34 +4935,35 @@ int blk_mq_update_nr_requests(struct request_queue *q, unsigned int nr)
 
 	blk_mq_quiesce_queue(q);
 
-	queue_for_each_hw_ctx(q, hctx, i) {
-		if (!hctx->tags)
-			continue;
-		/*
-		 * If we're using an MQ scheduler, just update the scheduler
-		 * queue depth. This is similar to what the old code would do.
-		 */
-		if (hctx->sched_tags) {
-			ret = blk_mq_tag_update_depth(hctx, &hctx->sched_tags,
-						      nr);
-		} else {
-			ret = blk_mq_tag_update_depth(hctx, &hctx->tags, nr);
-		}
-		if (ret)
-			goto out;
-	}
-
-	q->nr_requests = nr;
-	if (q->elevator && q->elevator->type->ops.depth_updated)
-		q->elevator->type->ops.depth_updated(q);
-
 	if (blk_mq_is_shared_tags(set->flags)) {
 		if (q->elevator)
 			blk_mq_tag_update_sched_shared_tags(q);
 		else
 			blk_mq_tag_resize_shared_tags(set, nr);
+	} else {
+		queue_for_each_hw_ctx(q, hctx, i) {
+			if (!hctx->tags)
+				continue;
+			/*
+			 * If we're using an MQ scheduler, just update the
+			 * scheduler queue depth. This is similar to what the
+			 * old code would do.
+			 */
+			if (hctx->sched_tags)
+				ret = blk_mq_tag_update_depth(hctx,
+							&hctx->sched_tags, nr);
+			else
+				ret = blk_mq_tag_update_depth(hctx,
+							&hctx->tags, nr);
+			if (ret)
+				goto out;
+		}
 	}
 
+	q->nr_requests = nr;
+	if (q->elevator && q->elevator->type->ops.depth_updated)
+		q->elevator->type->ops.depth_updated(q);
+
 out:
 	blk_mq_unquiesce_queue(q);