[PATCH] nvme: add namespace paths links

[Christoph Hellwig]

On Fri, Apr 01, 2022 at 11:28:55AM +0200, Hannes Reinecke wrote:
> It is really annoying to always have to loop through the entire
> /sys/block directory just to find the namespace path links for
> a single namespace in libnvme/nvme-cli.
> So provide links to the namespace paths for efficient lookup.

I think having some form of links would be useful.  Quite a while ago
Thadeu looked into adding some form of relationship for lsblk and
friends.  Maybe it would be good to sync up and make sure whatever
links we are adding would be useful for all users?

> 
> Signed-off-by: Hannes Reinecke <hare at suse.de>
> ---
>  drivers/nvme/host/core.c      | 3 +++
>  drivers/nvme/host/multipath.c | 8 ++++++++
>  2 files changed, 11 insertions(+)
> 
> diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
> index f204c6f78b5b..df4d89aa061f 100644
> --- a/drivers/nvme/host/core.c
> +++ b/drivers/nvme/host/core.c
> @@ -4054,6 +4054,9 @@ static void nvme_ns_remove(struct nvme_ns *ns)
>  
>  	if (!nvme_ns_head_multipath(ns->head))
>  		nvme_cdev_del(&ns->cdev, &ns->cdev_device);
> +	else
> +		sysfs_remove_link(&disk_to_dev(ns->head->disk)->kobj,
> +				  ns->disk->disk_name);
>  	del_gendisk(ns->disk);
>  	blk_cleanup_queue(ns->queue);
>  
> diff --git a/drivers/nvme/host/multipath.c b/drivers/nvme/host/multipath.c
> index 7fc58e1f6b09..dc9a4018f90d 100644
> --- a/drivers/nvme/host/multipath.c
> +++ b/drivers/nvme/host/multipath.c
> @@ -801,6 +801,8 @@ static int nvme_lookup_ana_group_desc(struct nvme_ctrl *ctrl,
>  
>  void nvme_mpath_add_disk(struct nvme_ns *ns, struct nvme_id_ns *id)
>  {
> +	int ret;
> +
>  	if (nvme_ctrl_use_ana(ns->ctrl)) {
>  		struct nvme_ana_group_desc desc = {
>  			.grpid = id->anagrpid,
> @@ -831,6 +833,12 @@ void nvme_mpath_add_disk(struct nvme_ns *ns, struct nvme_id_ns *id)
>  	if (blk_queue_is_zoned(ns->queue) && ns->head->disk)
>  		ns->head->disk->queue->nr_zones = ns->queue->nr_zones;
>  #endif
> +	ret = sysfs_create_link(&disk_to_dev(ns->head->disk)->kobj,
> +				&disk_to_dev(ns->disk)->kobj,
> +				ns->disk->disk_name);
> +	if (ret)
> +		dev_warn(ns->ctrl->device,
> +			 "failed to create namespace path link\n");
>  }
>  
>  void nvme_mpath_shutdown_disk(struct nvme_ns_head *head)
> -- 
> 2.29.2
---end quoted text---