mcb: Implement bus->dev.release callback

The mcb_bus structure previously was released in mcb_release_bus. This lead to
the following warning on module unload:

------------[ cut here ]------------
WARNING: CPU: 1 PID: 2032 at drivers/base/core.c:251 device_release+0x73/0x90
Device 'mcb:0' does not have a release() function, it is broken and must be fixed.
Modules linked in: men_z135_uart mcb_pci(-) mcb
CPU: 1 PID: 2032 Comm: rmmod Not tainted 4.6.0-rc4+ #3
Hardware name: N/A N/A/COMe-mBTi10, BIOS MVV1R921 X64 10/14/2015
 00000286 00000286 c0117de4 c12d6f16 c0117e2c c18be0d3 c0117dfc c104f6e1
 000000fb f5ccbe08 f5ccbe00 f5c64600 c0117e18 c104f728 00000009 00000000
 c0117e10 c18db674 c0117e2c c0117e3c c13ce5c3 c18be0d3 000000fb c18db674
Call Trace:
 [<c12d6f16>] dump_stack+0x47/0x61
 [<c104f6e1>] __warn+0xc1/0xe0
 [<c104f728>] warn_slowpath_fmt+0x28/0x30
 [<c13ce5c3>] device_release+0x73/0x90
 [<c12d92e4>] kobject_release+0x34/0x80
 [<c12d929d>] ? kobject_del+0x2d/0x40
 [<c12d9205>] kobject_put+0x25/0x50
 [<c13ce77f>] put_device+0xf/0x20
 [<c13d114b>] klist_devices_put+0xb/0x10
 [<c1752673>] klist_next+0x73/0xf0
 [<c13d1140>] ? unbind_store+0x100/0x100
 [<f8a23370>] ? mcb_bus_add_devices+0x30/0x30 [mcb]
 [<c13d0a81>] bus_for_each_dev+0x51/0x80
 [<f8a23319>] mcb_release_bus+0x19/0x40 [mcb]
 [<f8a23370>] ? mcb_bus_add_devices+0x30/0x30 [mcb]
 [<f8a2b033>] mcb_pci_remove+0x13/0x20 [mcb_pci]
 [<c130d358>] pci_device_remove+0x28/0xb0
 [<c13d201b>] __device_release_driver+0x7b/0x110
 [<c13d2847>] driver_detach+0x87/0x90
 [<c13d1b9b>] bus_remove_driver+0x3b/0x80
 [<c13d2ed0>] driver_unregister+0x20/0x50
 [<c130be53>] pci_unregister_driver+0x13/0x60
 [<f8a2b1f4>] mcb_pci_driver_exit+0xd/0xf [mcb_pci]
 [<c10be588>] SyS_delete_module+0x138/0x200
 [<c1159208>] ? ____fput+0x8/0x10
 [<c1068054>] ? task_work_run+0x74/0x90
 [<c1001879>] do_fast_syscall_32+0x69/0x120
 [<c1757597>] sysenter_past_esp+0x40/0x6a
---[ end trace 1ed34c2aa3019875 ]---

Release a mcb_bus' memory on the device's release callback, to avoid above
warning.

Signed-off-by: Johannes Thumshirn <jthumshirn@suse.de>
Reported-by: Andreas Werner <andreas.werner@men.de>
Tested-by: Andreas Werner <andreas.werner@men.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/mcb/mcb-core.c

@@ -83,8 +83,8 @@ static int mcb_remove(struct device *dev)
 
 static void mcb_shutdown(struct device *dev)
 {
+	struct mcb_driver *mdrv = to_mcb_driver(dev->driver);
 	struct mcb_device *mdev = to_mcb_device(dev);
-	struct mcb_driver *mdrv = mdev->driver;
 
 	if (mdrv && mdrv->shutdown)
 		mdrv->shutdown(mdev);
@@ -214,6 +214,7 @@ int mcb_device_register(struct mcb_bus *bus, struct mcb_device *dev)
 	int device_id;
 
 	device_initialize(&dev->dev);
+	mcb_bus_get(bus);
 	dev->dev.bus = &mcb_bus_type;
 	dev->dev.parent = bus->dev.parent;
 	dev->dev.release = mcb_release_dev;
@@ -237,6 +238,15 @@ out:
 }
 EXPORT_SYMBOL_GPL(mcb_device_register);
 
+static void mcb_free_bus(struct device *dev)
+{
+	struct mcb_bus *bus = to_mcb_bus(dev);
+
+	put_device(bus->carrier);
+	ida_simple_remove(&mcb_ida, bus->bus_nr);
+	kfree(bus);
+}
+
 /**
  * mcb_alloc_bus() - Allocate a new @mcb_bus
  *
@@ -259,12 +269,13 @@ struct mcb_bus *mcb_alloc_bus(struct device *carrier)
 	}
 
 	bus->bus_nr = bus_nr;
-	bus->carrier = carrier;
+	bus->carrier = get_device(carrier);
 
 	device_initialize(&bus->dev);
 	bus->dev.parent = carrier;
 	bus->dev.bus = &mcb_bus_type;
 	bus->dev.type = &mcb_carrier_device_type;
+	bus->dev.release = &mcb_free_bus;
 
 	dev_set_name(&bus->dev, "mcb:%d", bus_nr);
 	rc = device_add(&bus->dev);
@@ -273,6 +284,7 @@ struct mcb_bus *mcb_alloc_bus(struct device *carrier)
 
 	return bus;
 err_free:
+	put_device(carrier);
 	kfree(bus);
 	return ERR_PTR(rc);
 }
@@ -297,10 +309,6 @@ static void mcb_devices_unregister(struct mcb_bus *bus)
 void mcb_release_bus(struct mcb_bus *bus)
 {
 	mcb_devices_unregister(bus);
-
-	ida_simple_remove(&mcb_ida, bus->bus_nr);
-
-	kfree(bus);
 }
 EXPORT_SYMBOL_GPL(mcb_release_bus);