[PATCH RFC 20/39] xen-blkback: module_exit support

[Joao Martins <joao.m.martins@xxxxxxxxxx>]

Implement module_exit to allow users to do module unload of blkback.
We prevent users from module unload whenever there are still interfaces
allocated, in other words, do module_get on xen_blkif_alloc() and
module_put on xen_blkif_free().

Signed-off-by: Joao Martins <joao.m.martins@xxxxxxxxxx>
---
 drivers/block/xen-blkback/blkback.c |  8 ++++++++
 drivers/block/xen-blkback/common.h  |  2 ++
 drivers/block/xen-blkback/xenbus.c  | 14 ++++++++++++++
 3 files changed, 24 insertions(+)

diff --git a/drivers/block/xen-blkback/blkback.c b/drivers/block/xen-blkback/blkback.c
index fd1e19f1a49f..d51d88be88e1 100644
--- a/drivers/block/xen-blkback/blkback.c
+++ b/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_exit(void)
+{
+	xen_blkif_interface_exit();
+	xen_blkif_xenbus_exit();
+}
+
+module_exit(xen_blkif_exit);
+
 MODULE_LICENSE("Dual BSD/GPL");
 MODULE_ALIAS("xen-backend:vbd");
diff --git a/drivers/block/xen-blkback/common.h b/drivers/block/xen-blkback/common.h
index 1d3002d773f7..3415c558e115 100644
--- a/drivers/block/xen-blkback/common.h
+++ b/drivers/block/xen-blkback/common.h
@@ -376,8 +376,10 @@ struct phys_req {
 	blkif_sector_t		sector_number;
 };
 int xen_blkif_interface_init(void);
+void xen_blkif_interface_exit(void);
 
 int xen_blkif_xenbus_init(void);
+void xen_blkif_xenbus_exit(void);
 
 irqreturn_t xen_blkif_be_int(int irq, void *dev_id);
 int xen_blkif_schedule(void *arg);
diff --git a/drivers/block/xen-blkback/xenbus.c b/drivers/block/xen-blkback/xenbus.c
index a4bc74e72c39..424e2efebe85 100644
--- a/drivers/block/xen-blkback/xenbus.c
+++ b/drivers/block/xen-blkback/xenbus.c
@@ -181,6 +181,8 @@ static struct xen_blkif *xen_blkif_alloc(domid_t domid)
 	init_completion(&blkif->drain_complete);
 	INIT_WORK(&blkif->free_work, xen_blkif_deferred_free);
 
+	__module_get(THIS_MODULE);
+
 	return blkif;
 }
 
@@ -328,6 +330,8 @@ static void xen_blkif_free(struct xen_blkif *blkif)
 
 	/* Make sure everything is drained before shutting down */
 	kmem_cache_free(xen_blkif_cachep, blkif);
+
+	module_put(THIS_MODULE);
 }
 
 int __init xen_blkif_interface_init(void)
@@ -341,6 +345,11 @@ int __init xen_blkif_interface_init(void)
 	return 0;
 }
 
+void xen_blkif_interface_exit(void)
+{
+	kmem_cache_destroy(xen_blkif_cachep);
+}
+
 /*
  *  sysfs interface for VBD I/O requests
  */
@@ -1115,3 +1124,8 @@ int xen_blkif_xenbus_init(void)
 {
 	return xenbus_register_backend(&xen_blkbk_driver);
 }
+
+void xen_blkif_xenbus_exit(void)
+{
+	xenbus_unregister_driver(&xen_blkbk_driver);
+}
-- 
2.11.0