Re: [PATCH 01/13] block: freeze queue when updating zone resources

[Bart Van Assche <bvanassche@acm.org>]

On 10/30/25 11:12 PM, Damien Le Moal wrote:
> Modify disk_update_zone_resources() to freeze the device queue before
> updating the number of zones, zone capacity and other zone related
> resources. The locking order resulting from the call to
> queue_limits_commit_update_frozen() is preserved, that is, the queue
> limits lock is first taken by calling queue_limits_start_update() before
> freezing the queue, and the queue is unfrozen after executing
> queue_limits_commit_update(), which replaces the call to
> queue_limits_commit_update_frozen().
> 
> This change ensures that there are no in-flights I/Os when the zone
> resources are updated due to a zone revalidation.
> 
> Fixes: 0b83c86b444a ("block: Prevent potential deadlock in blk_revalidate_disk_zones()")
> Cc: stable@vger.kernel.org
> Signed-off-by: Damien Le Moal <dlemoal@kernel.org>
> ---
>   block/blk-zoned.c | 19 ++++++++++++++-----
>   1 file changed, 14 insertions(+), 5 deletions(-)
> 
> diff --git a/block/blk-zoned.c b/block/blk-zoned.c
> index 5e2a5788dc3b..f3b371056df4 100644
> --- a/block/blk-zoned.c
> +++ b/block/blk-zoned.c
> @@ -1516,8 +1516,13 @@ static int disk_update_zone_resources(struct gendisk *disk,
>   {
>   	struct request_queue *q = disk->queue;
>   	unsigned int nr_seq_zones, nr_conv_zones;
> -	unsigned int pool_size;
> +	unsigned int pool_size, memflags;
>   	struct queue_limits lim;
> +	int ret;
> +
> +	lim = queue_limits_start_update(q);
> +
> +	memflags = blk_mq_freeze_queue(q);
>   
>   	disk->nr_zones = args->nr_zones;
>   	disk->zone_capacity = args->zone_capacity;
> @@ -1527,11 +1532,10 @@ static int disk_update_zone_resources(struct gendisk *disk,
>   	if (nr_conv_zones >= disk->nr_zones) {
>   		pr_warn("%s: Invalid number of conventional zones %u / %u\n",
>   			disk->disk_name, nr_conv_zones, disk->nr_zones);
> -		return -ENODEV;
> +		ret = -ENODEV;
> +		goto unfreeze;
>   	}
>   
> -	lim = queue_limits_start_update(q);
> -
>   	/*
>   	 * Some devices can advertize zone resource limits that are larger than
>   	 * the number of sequential zones of the zoned block device, e.g. a
> @@ -1568,7 +1572,12 @@ static int disk_update_zone_resources(struct gendisk *disk,
>   	}
>   
>   commit:
> -	return queue_limits_commit_update_frozen(q, &lim);
> +	ret = queue_limits_commit_update(q, &lim);
> +
> +unfreeze:
> +	blk_mq_unfreeze_queue(q, memflags);
> +
> +	return ret;
>   }
>   
>   static int blk_revalidate_conv_zone(struct blk_zone *zone, unsigned int idx,

Hi Damien,

disk_update_zone_resources() only has a single caller and just below the
only call of this function the following code is present:

	if (ret) {
		unsigned int memflags = blk_mq_freeze_queue(q);

		disk_free_zone_resources(disk);
		blk_mq_unfreeze_queue(q, memflags);
	}

Shouldn't this code be moved into disk_update_zone_resources() such that
error handling happens without unfreezing and refreezing the request
queue?

Thanks,

Bart.