Re: [PATCH] block: Fix partition check for host-aware zoned block devices

[Christoph Hellwig <hch@lst.de>]

On Fri, Oct 15, 2021 at 11:07:40AM +0900, Shin'ichiro Kawasaki wrote:
> To fix the issues, call the helper function disk_has_partitions() in
> place of disk->part_tbl empty check. Since the function was removed with
> the commit a33df75c6328, reimplement it to walk through entries in the
> xarray disk->part_tbl.

Looks good,

Reviewed-by: Christoph Hellwig <hch@lst.de>

Matthew,

we talked about possiblig adding a xa_nr_entries helper a while ago.
This would be a good place for it, as we could just check
xa_nr_entries() > 1 for example.

> 
> Fixes: a33df75c6328 ("block: use an xarray for disk->part_tbl")
> Signed-off-by: Shin'ichiro Kawasaki <shinichiro.kawasaki@wdc.com>
> Cc: stable@vger.kernel.org # v5.14+
> ---
>  block/blk-settings.c | 20 +++++++++++++++++++-
>  1 file changed, 19 insertions(+), 1 deletion(-)
> 
> diff --git a/block/blk-settings.c b/block/blk-settings.c
> index a7c857ad7d10..b880c70e22e4 100644
> --- a/block/blk-settings.c
> +++ b/block/blk-settings.c
> @@ -842,6 +842,24 @@ bool blk_queue_can_use_dma_map_merging(struct request_queue *q,
>  }
>  EXPORT_SYMBOL_GPL(blk_queue_can_use_dma_map_merging);
>  
> +static bool disk_has_partitions(struct gendisk *disk)
> +{
> +	unsigned long idx;
> +	struct block_device *part;
> +	bool ret = false;
> +
> +	rcu_read_lock();
> +	xa_for_each(&disk->part_tbl, idx, part) {
> +		if (bdev_is_partition(part)) {
> +			ret = true;
> +			break;
> +		}
> +	}
> +	rcu_read_unlock();
> +
> +	return ret;
> +}
> +
>  /**
>   * blk_queue_set_zoned - configure a disk queue zoned model.
>   * @disk:	the gendisk of the queue to configure
> @@ -876,7 +894,7 @@ void blk_queue_set_zoned(struct gendisk *disk, enum blk_zoned_model model)
>  		 * we do nothing special as far as the block layer is concerned.
>  		 */
>  		if (!IS_ENABLED(CONFIG_BLK_DEV_ZONED) ||
> -		    !xa_empty(&disk->part_tbl))
> +		    disk_has_partitions(disk))
>  			model = BLK_ZONED_NONE;
>  		break;
>  	case BLK_ZONED_NONE:
> -- 
> 2.31.1
---end quoted text---