xen-blkback: allow module to be cleanly unloaded

Add a module_exit() to perform the necessary clean-up.
Signed-off-by: Paul Durrant <pdurrant@amazon.com>
Reviewed-by: "Roger Pau Monné" <roger.pau@citrix.com>
Reviewed-by: Juergen Gross <jgross@suse.com>
Signed-off-by: Juergen Gross <jgross@suse.com>

drivers/block/xen-blkback/blkback.c

@@ -1504,5 +1504,13 @@ static int __init xen_blkif_init(void)
 
 module_init(xen_blkif_init);
 
+static void __exit xen_blkif_fini(void)
+{
+	xen_blkif_xenbus_fini();
+	xen_blkif_interface_fini();
+}
+
+module_exit(xen_blkif_fini);
+
 MODULE_LICENSE("Dual BSD/GPL");
 MODULE_ALIAS("xen-backend:vbd");

drivers/block/xen-blkback/common.h

@@ -375,9 +375,12 @@ struct phys_req {
 	struct block_device	*bdev;
 	blkif_sector_t		sector_number;
 };
+
 int xen_blkif_interface_init(void);
+void xen_blkif_interface_fini(void);
 
 int xen_blkif_xenbus_init(void);
+void xen_blkif_xenbus_fini(void);
 
 irqreturn_t xen_blkif_be_int(int irq, void *dev_id);
 int xen_blkif_schedule(void *arg);

drivers/block/xen-blkback/xenbus.c

@@ -333,6 +333,12 @@ int __init xen_blkif_interface_init(void)
 	return 0;
 }
 
+void xen_blkif_interface_fini(void)
+{
+	kmem_cache_destroy(xen_blkif_cachep);
+	xen_blkif_cachep = NULL;
+}
+
 /*
  *  sysfs interface for VBD I/O requests
  */
@@ -1122,3 +1128,8 @@ int xen_blkif_xenbus_init(void)
 {
 	return xenbus_register_backend(&xen_blkbk_driver);
 }
+
+void xen_blkif_xenbus_fini(void)
+{
+	xenbus_unregister_driver(&xen_blkbk_driver);
+}