[PATCH] nvme: add namespace paths links

[Sagi Grimberg]

> 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.
> 
> Signed-off-by: Hannes Reinecke <hare at suse.de>
> ---
>   drivers/nvme/host/core.c      |  3 +++
>   drivers/nvme/host/multipath.c | 10 ++++++++++
>   2 files changed, 13 insertions(+)
> 
> diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
> index 37b6fa746662..88933838e067 100644
> --- a/drivers/nvme/host/core.c
> +++ b/drivers/nvme/host/core.c
> @@ -3681,6 +3681,9 @@ 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);
>   
>   	down_write(&ns->ctrl->namespaces_rwsem);
> diff --git a/drivers/nvme/host/multipath.c b/drivers/nvme/host/multipath.c
> index 0a88d7bdc5e3..9dd0be645dad 100644
> --- a/drivers/nvme/host/multipath.c
> +++ b/drivers/nvme/host/multipath.c
> @@ -875,6 +875,16 @@ void nvme_mpath_add_disk(struct nvme_ns *ns, __le32 anagrpid)
>   	if (blk_queue_is_zoned(ns->queue) && ns->head->disk)
>   		ns->head->disk->nr_zones = ns->disk->nr_zones;
>   #endif
> +	if (ns->head->disk) {

Why are the two conditions not identical?

> +		int ret;
> +
> +		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)

What will these links be used for?