[PATCH] nvme: add namespace paths links

[Hannes Reinecke]

On 9/12/23 14:55, 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?
> 
> ns->head->disk and nvme_ns_head_multipath()
> 
How can we have one without the other? I thought that both are mutually 
dependent .. but yeah, we should be using 'nvme_ns_head_multipath()' here.

>>
>>>> +        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.
> 
> you mean for nvme list -v ?
> 
> Don't really mind having it, but would want to hear from others as
> well.

Ok.

Cheers,

Hannes