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

Bart Van Assche
2025-10-31T17:48:23Z

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.