blk-mq: check invalid nr_requests in queue_requests_store()

queue_requests_store() is the only caller of
blk_mq_update_nr_requests(), and blk_mq_update_nr_requests() is the
only caller of blk_mq_tag_update_depth(), however, they all have
checkings for nr_requests input by user.

Make code cleaner by moving all the checkings to the top function:

1) nr_requests > reserved tags;
2) if there is elevator, 4 <= nr_requests <= 2048;
3) if elevator is none, 4 <= nr_requests <= tag_set->queue_depth;

Meanwhile, case 2 is the only case tags can grow and -ENOMEM might be
returned.

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

block/blk-mq-tag.c

@@ -610,14 +610,10 @@ void blk_mq_free_tags(struct blk_mq_tag_set *set, struct blk_mq_tags *tags)
 }
 
 int blk_mq_tag_update_depth(struct blk_mq_hw_ctx *hctx,
-			    struct blk_mq_tags **tagsptr, unsigned int tdepth,
+			    struct blk_mq_tags **tagsptr, unsigned int tdepth)
-			    bool can_grow)
 {
 	struct blk_mq_tags *tags = *tagsptr;
 
-	if (tdepth <= tags->nr_reserved_tags)
-		return -EINVAL;
-
 	/*
 	 * If we are allowed to grow beyond the original size, allocate
 	 * a new set of tags before freeing the old one.
@@ -626,16 +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;
 
-		if (!can_grow)
-			return -EINVAL;
-
-		/*
-		 * We need some sort of upper limit, set it high enough that
-		 * no valid use cases should require more.
-		 */
-		if (tdepth > MAX_SCHED_RQ)
-			return -EINVAL;
-
 		/*
 		 * Only the sbitmap needs resizing since we allocated the max
 		 * initially.

block/blk-mq.c

@@ -4933,9 +4933,6 @@ int blk_mq_update_nr_requests(struct request_queue *q, unsigned int nr)
 	int ret = 0;
 	unsigned long i;
 
-	if (q->nr_requests == nr)
-		return 0;
-
 	blk_mq_quiesce_queue(q);
 
 	queue_for_each_hw_ctx(q, hctx, i) {
@@ -4947,10 +4944,9 @@ int blk_mq_update_nr_requests(struct request_queue *q, unsigned int nr)
 		 */
 		if (hctx->sched_tags) {
 			ret = blk_mq_tag_update_depth(hctx, &hctx->sched_tags,
-						      nr, true);
+						      nr);
 		} else {
-			ret = blk_mq_tag_update_depth(hctx, &hctx->tags, nr,
+			ret = blk_mq_tag_update_depth(hctx, &hctx->tags, nr);
-						      false);
 		}
 		if (ret)
 			goto out;

block/blk-mq.h

@@ -171,7 +171,7 @@ void blk_mq_put_tag(struct blk_mq_tags *tags, struct blk_mq_ctx *ctx,
 		unsigned int tag);
 void blk_mq_put_tags(struct blk_mq_tags *tags, int *tag_array, int nr_tags);
 int blk_mq_tag_update_depth(struct blk_mq_hw_ctx *hctx,
-		struct blk_mq_tags **tags, unsigned int depth, bool can_grow);
+		struct blk_mq_tags **tags, unsigned int depth);
 void blk_mq_tag_resize_shared_tags(struct blk_mq_tag_set *set,
 		unsigned int size);
 void blk_mq_tag_update_sched_shared_tags(struct request_queue *q);

block/blk-sysfs.c

@@ -75,12 +75,25 @@ queue_requests_store(struct gendisk *disk, const char *page, size_t count)
 
 	memflags = blk_mq_freeze_queue(q);
 	mutex_lock(&q->elevator_lock);
+
+	if (nr == q->nr_requests)
+		goto unlock;
+
 	if (nr < BLKDEV_MIN_RQ)
 		nr = BLKDEV_MIN_RQ;
 
+	if (nr <= q->tag_set->reserved_tags ||
+	    (q->elevator && nr > MAX_SCHED_RQ) ||
+	    (!q->elevator && nr > q->tag_set->queue_depth)) {
+		ret = -EINVAL;
+		goto unlock;
+	}
+
 	err = blk_mq_update_nr_requests(disk->queue, nr);
 	if (err)
 		ret = err;
+
+unlock:
 	mutex_unlock(&q->elevator_lock);
 	blk_mq_unfreeze_queue(q, memflags);
 	return ret;