linux-kernel - [PATCH for-6.18/block 03/10] blk-mq: check invalid nr_requests in queue_requests

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Message-Id: <20250908061533.3062917-4-yukuai1@huaweicloud.com>
Date: Mon,  8 Sep 2025 14:15:26 +0800
From: Yu Kuai <yukuai1@...weicloud.com>
To: nilay@...ux.ibm.com,
	ming.lei@...hat.com,
	axboe@...nel.dk
Cc: linux-block@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	yukuai3@...wei.com,
	yukuai1@...weicloud.com,
	yi.zhang@...wei.com,
	yangerkun@...wei.com,
	johnny.chenyi@...wei.com
Subject: [PATCH for-6.18/block 03/10] blk-mq: check invalid nr_requests in queue_requests_store()

From: Yu Kuai <yukuai3@...wei.com>

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@...wei.com>
---
 block/blk-mq-tag.c | 16 +---------------
 block/blk-mq.c     |  8 ++------
 block/blk-mq.h     |  2 +-
 block/blk-sysfs.c  | 13 +++++++++++++
 4 files changed, 17 insertions(+), 22 deletions(-)

diff --git a/block/blk-mq-tag.c b/block/blk-mq-tag.c
index 5cffa5668d0c..725210f27471 100644
--- a/block/blk-mq-tag.c
+++ b/block/blk-mq-tag.c
@@ -584,14 +584,10 @@ void blk_mq_free_tags(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,
-			    bool can_grow)
+			    struct blk_mq_tags **tagsptr, unsigned int tdepth)
 {
 	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.
@@ -600,16 +596,6 @@ 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.
diff --git a/block/blk-mq.c b/block/blk-mq.c
index 0fac0236a5dc..d7540b8e7471 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -4924,9 +4924,6 @@ 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) {
@@ -4938,10 +4935,9 @@ 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,
-						      false);
+			ret = blk_mq_tag_update_depth(hctx, &hctx->tags, nr);
 		}
 		if (ret)
 			goto out;
diff --git a/block/blk-mq.h b/block/blk-mq.h
index affb2e14b56e..2b3ade60c90b 100644
--- a/block/blk-mq.h
+++ b/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);
diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c
index 1ffa65feca4f..f99519f7a820 100644
--- a/block/blk-sysfs.c
+++ b/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;
-- 
2.39.2