[dm-devel] [PATCH 7/8] dm: delay registering the gendisk

[Mike Snitzer]

On Sun, Jul 25 2021 at  1:54P -0400,
Christoph Hellwig <hch at lst.de> wrote:

> device mapper is currently the only outlier that tries to call
> register_disk after add_disk, leading to fairly inconsistent state
> of these block layer data structures.  Instead change device-mapper
> to just register the gendisk later now that the holder mechanism
> can cope with that.
> 
> Note that this introduces a user visible change: the dm kobject is
> now only visible after the initial table has been loaded.
> 
> Signed-off-by: Christoph Hellwig <hch at lst.de>

Reviewed-by: Mike Snitzer <snitzer at redhat.com>

Jens, feel free to pick this series up once you're comfortable with it.

Thanks,
Mike


> ---
>  drivers/md/dm-rq.c |  1 -
>  drivers/md/dm.c    | 23 +++++++++++------------
>  2 files changed, 11 insertions(+), 13 deletions(-)
> 
> diff --git a/drivers/md/dm-rq.c b/drivers/md/dm-rq.c
> index 0dbd48cbdff9..5b95eea517d1 100644
> --- a/drivers/md/dm-rq.c
> +++ b/drivers/md/dm-rq.c
> @@ -559,7 +559,6 @@ int dm_mq_init_request_queue(struct mapped_device *md, struct dm_table *t)
>  	err = blk_mq_init_allocated_queue(md->tag_set, md->queue);
>  	if (err)
>  		goto out_tag_set;
> -	elevator_init_mq(md->queue);
>  	return 0;
>  
>  out_tag_set:
> diff --git a/drivers/md/dm.c b/drivers/md/dm.c
> index f003bd5b93ce..7981b7287628 100644
> --- a/drivers/md/dm.c
> +++ b/drivers/md/dm.c
> @@ -1693,7 +1693,10 @@ static void cleanup_mapped_device(struct mapped_device *md)
>  		spin_lock(&_minor_lock);
>  		md->disk->private_data = NULL;
>  		spin_unlock(&_minor_lock);
> -		del_gendisk(md->disk);
> +		if (dm_get_md_type(md) != DM_TYPE_NONE) {
> +			dm_sysfs_exit(md);
> +			del_gendisk(md->disk);
> +		}
>  		dm_queue_destroy_keyslot_manager(md->queue);
>  		blk_cleanup_disk(md->disk);
>  	}
> @@ -1788,7 +1791,6 @@ static struct mapped_device *alloc_dev(int minor)
>  			goto bad;
>  	}
>  
> -	add_disk_no_queue_reg(md->disk);
>  	format_dev_t(md->name, MKDEV(_major, minor));
>  
>  	md->wq = alloc_workqueue("kdmflush", WQ_MEM_RECLAIM, 0);
> @@ -1989,19 +1991,12 @@ static struct dm_table *__unbind(struct mapped_device *md)
>   */
>  int dm_create(int minor, struct mapped_device **result)
>  {
> -	int r;
>  	struct mapped_device *md;
>  
>  	md = alloc_dev(minor);
>  	if (!md)
>  		return -ENXIO;
>  
> -	r = dm_sysfs_init(md);
> -	if (r) {
> -		free_dev(md);
> -		return r;
> -	}
> -
>  	*result = md;
>  	return 0;
>  }
> @@ -2081,10 +2076,15 @@ int dm_setup_md_queue(struct mapped_device *md, struct dm_table *t)
>  	r = dm_table_set_restrictions(t, md->queue, &limits);
>  	if (r)
>  		return r;
> -	md->type = type;
>  
> -	blk_register_queue(md->disk);
> +	add_disk(md->disk);
>  
> +	r = dm_sysfs_init(md);
> +	if (r) {
> +		del_gendisk(md->disk);
> +		return r;
> +	}
> +	md->type = type;
>  	return 0;
>  }
>  
> @@ -2190,7 +2190,6 @@ static void __dm_destroy(struct mapped_device *md, bool wait)
>  		DMWARN("%s: Forcibly removing mapped_device still in use! (%d users)",
>  		       dm_device_name(md), atomic_read(&md->holders));
>  
> -	dm_sysfs_exit(md);
>  	dm_table_destroy(__unbind(md));
>  	free_dev(md);
>  }
> -- 
> 2.30.2
>