driver core: bus: convert bus_create/remove_file to be constant

bus_create_file() and bus_remove_file() can be made to take a constant
bus pointer, as it should not be modifying anything in the bus
structure.  Make this change and move the functions to use the internal
subsys_get/put() logic as well, to prevent the use of the back-pointer
in struct bus_type.

Cc: "Rafael J. Wysocki" <rafael@kernel.org>
Link: https://lore.kernel.org/r/20230208111330.439504-5-gregkh@linuxfoundation.orgSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/base/bus.c

@@ -175,24 +175,30 @@ static const struct sysfs_ops bus_sysfs_ops = {
 	.store	= bus_attr_store,
 };
 
-int bus_create_file(struct bus_type *bus, struct bus_attribute *attr)
+int bus_create_file(const struct bus_type *bus, struct bus_attribute *attr)
 {
+	struct subsys_private *sp = bus_to_subsys(bus);
 	int error;
-	if (bus_get(bus)) {
-		error = sysfs_create_file(&bus->p->subsys.kobj, &attr->attr);
-		bus_put(bus);
-	} else
-		error = -EINVAL;
+
+	if (!sp)
+		return -EINVAL;
+
+	error = sysfs_create_file(&sp->subsys.kobj, &attr->attr);
+
+	subsys_put(sp);
 	return error;
 }
 EXPORT_SYMBOL_GPL(bus_create_file);
 
-void bus_remove_file(struct bus_type *bus, struct bus_attribute *attr)
+void bus_remove_file(const struct bus_type *bus, struct bus_attribute *attr)
 {
-	if (bus_get(bus)) {
-		sysfs_remove_file(&bus->p->subsys.kobj, &attr->attr);
-		bus_put(bus);
-	}
+	struct subsys_private *sp = bus_to_subsys(bus);
+
+	if (!sp)
+		return;
+
+	sysfs_remove_file(&sp->subsys.kobj, &attr->attr);
+	subsys_put(sp);
 }
 EXPORT_SYMBOL_GPL(bus_remove_file);
 

include/linux/device/bus.h

@@ -135,9 +135,8 @@ struct bus_attribute {
 #define BUS_ATTR_WO(_name) \
 	struct bus_attribute bus_attr_##_name = __ATTR_WO(_name)
 
-extern int __must_check bus_create_file(struct bus_type *,
-					struct bus_attribute *);
-extern void bus_remove_file(struct bus_type *, struct bus_attribute *);
+int __must_check bus_create_file(const struct bus_type *bus, struct bus_attribute *attr);
+void bus_remove_file(const struct bus_type *bus, struct bus_attribute *attr);
 
 /* Generic device matching functions that all busses can use to match with */
 int device_match_name(struct device *dev, const void *name);