mm: add numa node symlink for cpu devices in sysfs

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.

Signed-off-by: Alex Chiang <achiang@hp.com>
Acked-by: David Rientjes <rientjes@google.com>
Cc: Gary Hade <garyhade@us.ibm.com>
Cc: Badari Pulavarty <pbadari@us.ibm.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: David Rientjes <rientjes@google.com>
Cc: Greg KH <greg@kroah.com>
Cc: Randy Dunlap <randy.dunlap@oracle.com>
Cc: David Rientjes <rientjes@google.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/drivers/base/node.c b/drivers/base/node.c
index 9b9acc3..4141411 100644 (file)
--- a/drivers/base/node.c
+++ b/drivers/base/node.c
@@ -271,6 +271,7 @@ 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))
@@ -280,9 +281,15 @@ 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)
@@ -298,6 +305,8 @@ 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;
 }