[PATCH] nvme: add namespace paths links

[Hannes Reinecke]

On 9/12/23 13:43, Sagi Grimberg 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.
>>
>> 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?
> 
Which two?

>> +        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?

Mapping for nvme-cli, as explained in the description.
Clearly it doesn't do it _now_, but once the patch is in we can
simplify nvme-cli to take advantage of it.

Cheers,

Hannes