It is confusing that device-dax instances publish a 'target_node'
attribute, but not a 'numa_node'. The 'numa_node' information is
available elsewhere in the sysfs device hierarchy, but it is not obvious
and not reliable from one device-dax instance-type (e.g. child devices
of nvdimm namespaces) to the next (e.g. 'hmem' devices defined by EFI
Specific Purpose Memory and the ACPI HMAT).

Cc: Ira Weiny <[email protected]>
Cc: Vishal Verma <[email protected]>
Signed-off-by: Dan Williams <[email protected]>
---
 drivers/dax/bus.c |   10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/drivers/dax/bus.c b/drivers/dax/bus.c
index ce6d648d7670..0879b9663eb7 100644
--- a/drivers/dax/bus.c
+++ b/drivers/dax/bus.c
@@ -322,6 +322,13 @@ static ssize_t modalias_show(struct device *dev, struct 
device_attribute *attr,
 }
 static DEVICE_ATTR_RO(modalias);
 
+static ssize_t numa_node_show(struct device *dev,
+               struct device_attribute *attr, char *buf)
+{
+       return sprintf(buf, "%d\n", dev_to_node(dev));
+}
+static DEVICE_ATTR_RO(numa_node);
+
 static umode_t dev_dax_visible(struct kobject *kobj, struct attribute *a, int 
n)
 {
        struct device *dev = container_of(kobj, struct device, kobj);
@@ -329,6 +336,8 @@ static umode_t dev_dax_visible(struct kobject *kobj, struct 
attribute *a, int n)
 
        if (a == &dev_attr_target_node.attr && dev_dax_target_node(dev_dax) < 0)
                return 0;
+       if (a == &dev_attr_numa_node.attr && !IS_ENABLED(CONFIG_NUMA))
+               return 0;
        return a->mode;
 }
 
@@ -337,6 +346,7 @@ static struct attribute *dev_dax_attributes[] = {
        &dev_attr_size.attr,
        &dev_attr_target_node.attr,
        &dev_attr_resource.attr,
+       &dev_attr_numa_node.attr,
        NULL,
 };
 
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