FAILED: patch "[PATCH] powerpc/sysfs: Fix reference leak of cpu device_nodes present" failed to apply to 4.9-stable tree

The patch below does not apply to the 4.9-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From: Tyrel Datwyler <[email protected]>
Date: Mon, 17 Apr 2017 20:24:39 -0400
Subject: [PATCH] powerpc/sysfs: Fix reference leak of cpu device_nodes present
at boot

For CPUs present at boot each logical CPU acquires a reference to the associated device node of the core. This happens in register_cpu() which is called by topology_init(). The result of this is that we end up with a reference held by each thread of the core. However, these references are never freed if the CPU core is DLPAR removed.

This patch fixes the reference leaks by acquiring and releasing the references in the CPU hotplug callbacks un/register_cpu_online(). With this patch symmetric reference counting is observed with both CPUs present at boot, and those DLPAR added after boot.

index c1fb255a60d6..949957b97ead 100644
@@ -710,6 +710,10 @@ static int register_cpu_online(unsigned int cpu)
 	struct device_attribute *attrs, *pmc_attrs;
 	int i, nattrs;
 
+	/* For cpus present at boot a reference was already grabbed in register_cpu() */
+	if (!s->of_node)
+		s->of_node = of_get_cpu_node(cpu, NULL);
+
 #ifdef CONFIG_PPC64
 	if (cpu_has_feature(CPU_FTR_SMT))
 		device_create_file(s, &dev_attr_smt_snooze_delay);

@@ -864,6 +868,8 @@ static int unregister_cpu_online(unsigned int cpu)
 	}
 #endif
 	cacheinfo_cpu_offline(cpu);
+	of_node_put(s->of_node);
+	s->of_node = NULL;
 #endif /* CONFIG_HOTPLUG_CPU */
 	return 0;
 }