[dm-devel] [for-4.16 PATCH v3 1/3] block: only bdi_unregister() in del_gendisk() if !GENHD_FL_HIDDEN

[Hannes Reinecke]

On 01/11/2018 03:12 AM, Mike Snitzer wrote:
> device_add_disk() will only call bdi_register_owner() if
> !GENHD_FL_HIDDEN, so it follows that del_gendisk() should only call
> bdi_unregister() if !GENHD_FL_HIDDEN.
> 
> Found with code inspection.  bdi_unregister() won't do any harm if
> bdi_register_owner() wasn't used but best to avoid the unnecessary
> call to bdi_unregister().
> 
> Fixes: 8ddcd65325 ("block: introduce GENHD_FL_HIDDEN")
> Signed-off-by: Mike Snitzer <snitzer at redhat.com>
> ---
>  block/genhd.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/block/genhd.c b/block/genhd.c
> index 96a66f671720..00620e01e043 100644
> --- a/block/genhd.c
> +++ b/block/genhd.c
> @@ -725,7 +725,8 @@ void del_gendisk(struct gendisk *disk)
>  		 * Unregister bdi before releasing device numbers (as they can
>  		 * get reused and we'd get clashes in sysfs).
>  		 */
> -		bdi_unregister(disk->queue->backing_dev_info);
> +		if (!(disk->flags & GENHD_FL_HIDDEN))
> +			bdi_unregister(disk->queue->backing_dev_info);
>  		blk_unregister_queue(disk);
>  	} else {
>  		WARN_ON(1);
> 
Reviewed-by: Hannes Reinecke <hare at suse.com>

Cheers,

Hannes
-- 
Dr. Hannes Reinecke		   Teamlead Storage & Networking
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