[PATCH] nvme: Create 'slaves' and 'holders' entries

[hch@lst.de (Christoph Hellwig)]

On Thu, Nov 09, 2017@05:57:06PM +0100, Hannes Reinecke wrote:
> When creating nvme multipath devices we should populate the
> 'slaves' and 'holders' directorys properly to aid userspace
> topology detection.
> 
> Patch is relative to hch's nvme-mpath branch

Hmm, what does this buy you given the hidden gendisk does not 
actually have a block device?  I'm not really opposed, but I also
don't see a use case for it.

If Jens is fine with this I'll add it after splitting it into block
and nvme parts, and merge the multipath patches for tomorrows nvme pull
request.

Can you give a formal ACK or should I take the implicit one from the
last comment?

> 
> Signed-off-by: Hannes Reinecke <hare at suse.com>
> ---
>  block/genhd.c            | 14 +++++++-------
>  drivers/nvme/host/core.c | 26 ++++++++++++++++++++++++++
>  2 files changed, 33 insertions(+), 7 deletions(-)
> 
> diff --git a/block/genhd.c b/block/genhd.c
> index 835e907..3de1671 100644
> --- a/block/genhd.c
> +++ b/block/genhd.c
> @@ -585,14 +585,14 @@ static void register_disk(struct device *parent, struct gendisk *disk)
>  	 */
>  	pm_runtime_set_memalloc_noio(ddev, true);
>  
> +	disk->part0.holder_dir = kobject_create_and_add("holders", &ddev->kobj);
> +	disk->slave_dir = kobject_create_and_add("slaves", &ddev->kobj);
> +
>  	if (disk->flags & GENHD_FL_HIDDEN) {
>  		dev_set_uevent_suppress(ddev, 0);
>  		return;
>  	}
>  
> -	disk->part0.holder_dir = kobject_create_and_add("holders", &ddev->kobj);
> -	disk->slave_dir = kobject_create_and_add("slaves", &ddev->kobj);
> -
>  	/* No minors to use for partitions */
>  	if (!disk_part_scan_enabled(disk))
>  		goto exit;
> @@ -728,11 +728,11 @@ void del_gendisk(struct gendisk *disk)
>  		WARN_ON(1);
>  	}
>  
> -	if (!(disk->flags & GENHD_FL_HIDDEN)) {
> +	if (!(disk->flags & GENHD_FL_HIDDEN))
>  		blk_unregister_region(disk_devt(disk), disk->minors);
> -		kobject_put(disk->part0.holder_dir);
> -		kobject_put(disk->slave_dir);
> -	}
> +
> +	kobject_put(disk->part0.holder_dir);
> +	kobject_put(disk->slave_dir);
>  
>  	part_stat_set_all(&disk->part0, 0);
>  	disk->part0.stamp = 0;
> diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
> index 9209b8b..6e9effa 100644
> --- a/drivers/nvme/host/core.c
> +++ b/drivers/nvme/host/core.c
> @@ -2756,6 +2756,22 @@ static void nvme_alloc_ns(struct nvme_ctrl *ctrl, unsigned nsid)
>  
>  	if (new)
>  		nvme_mpath_add_disk(ns->head);
> +
> +	if (ns->head->disk) {
> +		struct kobject *slave_disk_kobj, *holder_disk_kobj;
> +
> +		slave_disk_kobj = &disk_to_dev(ns->disk)->kobj;
> +		if (sysfs_create_link(ns->head->disk->slave_dir,
> +				      slave_disk_kobj,
> +				      kobject_name(slave_disk_kobj)))
> +			return;
> +		holder_disk_kobj = &disk_to_dev(ns->head->disk)->kobj;
> +		if (sysfs_create_link(ns->disk->part0.holder_dir,
> +				      holder_disk_kobj,
> +				      kobject_name(holder_disk_kobj)))
> +			sysfs_remove_link(ns->head->disk->slave_dir,
> +					  kobject_name(slave_disk_kobj));
> +	}
>  	return;
>   out_unlink_ns:
>  	mutex_lock(&ctrl->subsys->lock);
> @@ -2779,6 +2795,16 @@ static void nvme_ns_remove(struct nvme_ns *ns)
>  	if (ns->disk && ns->disk->flags & GENHD_FL_UP) {
>  		if (blk_get_integrity(ns->disk))
>  			blk_integrity_unregister(ns->disk);
> +		if (head->disk) {
> +			struct kobject *holder_disk_kobj =
> +				&disk_to_dev(head->disk)->kobj;
> +			struct kobject *slave_disk_kobj =
> +				&disk_to_dev(ns->disk)->kobj;
> +			sysfs_remove_link(ns->disk->part0.holder_dir,
> +					  kobject_name(holder_disk_kobj));
> +			sysfs_remove_link(ns->head->disk->slave_dir,
> +					  kobject_name(slave_disk_kobj));
> +		}
>  		sysfs_remove_group(&disk_to_dev(ns->disk)->kobj,
>  					&nvme_ns_id_attr_group);
>  		if (ns->ndev)
> -- 
> 1.8.5.6
---end quoted text---