linux-kernel - Re: [PATCH v2 13/18] libnvdimm: Export the target_node attribute for regions and namespaces

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Message-ID: <87zhgth61l.fsf@linux.ibm.com>
Date:   Mon, 18 Nov 2019 15:15:10 +0530
From:   "Aneesh Kumar K.V" <aneesh.kumar@...ux.ibm.com>
To:     Dan Williams <dan.j.williams@...el.com>, linux-nvdimm@...ts.01.org
Cc:     peterz@...radead.org, vishal.l.verma@...el.com,
        dave.hansen@...ux.intel.com, hch@....de,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        linux-acpi@...r.kernel.org
Subject: Re: [PATCH v2 13/18] libnvdimm: Export the target_node attribute for regions and namespaces

Dan Williams <dan.j.williams@...el.com> writes:

> Aneesh points out that some platforms may have "local" attached
> persistent memory and "remote" persistent memory that map to the same
> "online" node, or persistent memory devices with different performance
> properties. In this case 'numa_node' is identical for the two instances,
> but 'target_node' is differentiated so platform firmware can communicate
> distinct performance properties per range. Expose 'target_node' by
> default to allow for disambiguation of devices that share the same
> numa_map_to_online_node() result.
>

Reviewed-by: Aneesh Kumar K.V <aneesh.kumar@...ux.ibm.com>

> Reported-by: "Aneesh Kumar K.V" <aneesh.kumar@...ux.ibm.com>
> Signed-off-by: Dan Williams <dan.j.williams@...el.com>
> ---
>  drivers/nvdimm/bus.c |   29 +++++++++++++++++++++++++++++
>  1 file changed, 29 insertions(+)
>
> diff --git a/drivers/nvdimm/bus.c b/drivers/nvdimm/bus.c
> index 1d330d46d036..f76d709426f7 100644
> --- a/drivers/nvdimm/bus.c
> +++ b/drivers/nvdimm/bus.c
> @@ -685,17 +685,46 @@ static ssize_t numa_node_show(struct device *dev,
>  }
>  static DEVICE_ATTR_RO(numa_node);
>  
> +static int nvdimm_dev_to_target_node(struct device *dev)
> +{
> +	struct device *parent = dev->parent;
> +	struct nd_region *nd_region = NULL;
> +
> +	if (is_nd_region(dev))
> +		nd_region = to_nd_region(dev);
> +	else if (parent && is_nd_region(parent))
> +		nd_region = to_nd_region(parent);
> +
> +	if (!nd_region)
> +		return NUMA_NO_NODE;
> +	return nd_region->target_node;
> +}
> +
> +static ssize_t target_node_show(struct device *dev,
> +		struct device_attribute *attr, char *buf)
> +{
> +	return sprintf(buf, "%d\n", nvdimm_dev_to_target_node(dev));
> +}
> +static DEVICE_ATTR_RO(target_node);
> +
>  static struct attribute *nd_numa_attributes[] = {
>  	&dev_attr_numa_node.attr,
> +	&dev_attr_target_node.attr,
>  	NULL,
>  };
>  
>  static umode_t nd_numa_attr_visible(struct kobject *kobj, struct attribute *a,
>  		int n)
>  {
> +	struct device *dev = container_of(kobj, typeof(*dev), kobj);
> +
>  	if (!IS_ENABLED(CONFIG_NUMA))
>  		return 0;
>  
> +	if (a == &dev_attr_target_node.attr &&
> +			nvdimm_dev_to_target_node(dev) == NUMA_NO_NODE)
> +		return 0;
> +
>  	return a->mode;
>  }
>