[PATCH v3 4/5] mm: add numa node symlink for cpu devices in sysfs

[Alex Chiang <achiang@hp.com>]

You can discover which CPUs belong to a NUMA node by examining
/sys/devices/system/node/node#/

However, it's not convenient to go in the other direction, when looking at
/sys/devices/system/cpu/cpu#/

Yes, you can muck about in sysfs, but adding these symlinks makes
life a lot more convenient.

Acked-by: David Rientjes <rientjes@google.com>
Signed-off-by: Alex Chiang <achiang@hp.com>
---

 drivers/base/node.c |   11 ++++++++++-
 1 files changed, 10 insertions(+), 1 deletions(-)

diff --git a/drivers/base/node.c b/drivers/base/node.c
index ffda067..24fa962 100644
--- a/drivers/base/node.c
+++ b/drivers/base/node.c
@@ -227,6 +227,7 @@ struct node node_devices[MAX_NUMNODES];
  */
 int register_cpu_under_node(unsigned int cpu, unsigned int nid)
 {
+	int ret;
 	struct sys_device *obj;
 
 	if (!node_online(nid))
@@ -236,9 +237,15 @@ int register_cpu_under_node(unsigned int cpu, unsigned int nid)
 	if (!obj)
 		return 0;
 
-	return sysfs_create_link(&node_devices[nid].sysdev.kobj,
+	ret = sysfs_create_link(&node_devices[nid].sysdev.kobj,
 				&obj->kobj,
 				kobject_name(&obj->kobj));
+	if (ret)
+		return ret;
+
+	return sysfs_create_link(&obj->kobj,
+				 &node_devices[nid].sysdev.kobj,
+				 kobject_name(&node_devices[nid].sysdev.kobj));
 }
 
 int unregister_cpu_under_node(unsigned int cpu, unsigned int nid)
@@ -254,6 +261,8 @@ int unregister_cpu_under_node(unsigned int cpu, unsigned int nid)
 
 	sysfs_remove_link(&node_devices[nid].sysdev.kobj,
 			  kobject_name(&obj->kobj));
+	sysfs_remove_link(&obj->kobj,
+			  kobject_name(&node_devices[nid].sysdev.kobj));
 
 	return 0;
 }

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