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

Ming Lei
2018-01-11T02:48:20Z

On Wed, Jan 10, 2018 at 09:12:54PM -0500, 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@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);
> --
> 2.15.0
>

Reviewed-by: Ming Lei <ming.lei@redhat.com>

--
Ming