cpu/hotplug: move to use bus_get_dev_root()

JIRA: https://issues.redhat.com/browse/RHEL-1023

commit db281d5
Author: Greg Kroah-Hartman <[email protected]>
Date:   Mon Mar 13 19:28:49 2023 +0100

Direct access to the struct bus_type dev_root pointer is going away soon
so replace that with a call to bus_get_dev_root() instead, which is what
it is there for.

Cc: Thomas Gleixner <[email protected]>
Cc: Valentin Schneider <[email protected]>
Cc: Phil Auld <[email protected]>
Cc: Steven Price <[email protected]>
Cc: Juri Lelli <[email protected]>
Cc: Greg Kroah-Hartman <[email protected]>
Cc: Vincent Donnefort <[email protected]>
Cc: Kuppuswamy Sathyanarayanan <[email protected]>
Cc: "Jason A. Donenfeld" <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Greg Kroah-Hartman <[email protected]>
Signed-off-by: Mark Langsdorf <[email protected]>

Author: mlangsdorf

kernel/cpu.c

@@ -2521,22 +2521,33 @@ static const struct attribute_group cpuhp_smt_attr_group = {
 
 static int __init cpu_smt_sysfs_init(void)
 {
-	return sysfs_create_group(&cpu_subsys.dev_root->kobj,
-				  &cpuhp_smt_attr_group);
+	struct device *dev_root;
+	int ret = -ENODEV;
+
+	dev_root = bus_get_dev_root(&cpu_subsys);
+	if (dev_root) {
+		ret = sysfs_create_group(&dev_root->kobj, &cpuhp_smt_attr_group);
+		put_device(dev_root);
+	}
+	return ret;
 }
 
 static int __init cpuhp_sysfs_init(void)
 {
+	struct device *dev_root;
 	int cpu, ret;
 
 	ret = cpu_smt_sysfs_init();
 	if (ret)
 		return ret;
 
-	ret = sysfs_create_group(&cpu_subsys.dev_root->kobj,
-				 &cpuhp_cpu_root_attr_group);
-	if (ret)
-		return ret;
+	dev_root = bus_get_dev_root(&cpu_subsys);
+	if (dev_root) {
+		ret = sysfs_create_group(&dev_root->kobj, &cpuhp_cpu_root_attr_group);
+		put_device(dev_root);
+		if (ret)
+			return ret;
+	}
 
 	for_each_possible_cpu(cpu) {
 		struct device *dev = get_cpu_device(cpu);