linux-kernel - [PATCH] xen-blkback: allow module to be cleanly unloaded

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Message-ID: <20191129113131.1954-1-pdurrant@amazon.com>
Date:   Fri, 29 Nov 2019 11:31:31 +0000
From:   Paul Durrant <pdurrant@...zon.com>
To:     <xen-devel@...ts.xenproject.org>, <linux-block@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>
CC:     Paul Durrant <pdurrant@...zon.com>,
        Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
        Roger Pau Monné <roger.pau@...rix.com>,
        Jens Axboe <axboe@...nel.dk>
Subject: [PATCH] xen-blkback: allow module to be cleanly unloaded

Add a module_exit() to perform the necessary clean-up. Also add
__module_get() and module_put() calls into xen_blkif_alloc() and
xen_blkif_free() respectively to make sure an in-use module cannot be
unloaded.

Signed-off-by: Paul Durrant <pdurrant@...zon.com>
---
Cc: Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
Cc: "Roger Pau Monné" <roger.pau@...rix.com>
Cc: Jens Axboe <axboe@...nel.dk>
---
 drivers/block/xen-blkback/blkback.c |  8 ++++++++
 drivers/block/xen-blkback/common.h  |  3 +++
 drivers/block/xen-blkback/xenbus.c  | 15 +++++++++++++++
 3 files changed, 26 insertions(+)

diff --git a/drivers/block/xen-blkback/blkback.c b/drivers/block/xen-blkback/blkback.c
index fd1e19f1a49f..e562a7e20c3c 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_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");
diff --git a/drivers/block/xen-blkback/common.h b/drivers/block/xen-blkback/common.h
index 1d3002d773f7..49132b0adbbe 100644
--- a/drivers/block/xen-blkback/common.h
+++ b/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);
diff --git a/drivers/block/xen-blkback/xenbus.c b/drivers/block/xen-blkback/xenbus.c
index b90dbcd99c03..f948584fcf66 100644
--- a/drivers/block/xen-blkback/xenbus.c
+++ b/drivers/block/xen-blkback/xenbus.c
@@ -173,6 +173,8 @@ 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;
 }
 
@@ -320,6 +322,8 @@ 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)
@@ -333,6 +337,12 @@ 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 +1132,8 @@ 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);
+}
-- 
2.20.1