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 <[email protected]>
---
Cc: Konrad Rzeszutek Wilk <[email protected]>
Cc: "Roger Pau Monné" <[email protected]>
Cc: Jens Axboe <[email protected]>
---
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
On 29.11.2019 12:31, Paul Durrant wrote:
> --- 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);
> }
I realize there are various example of this in the tree, but
isn't this a flawed approach? __module_get() (nor even
try_module_get()) will prevent an unload attempt ahead of it
getting invoked, while execution is already in this module's
.text section. I think the xenbus driver should do this
before calling ->probe(), in case of its failure, and after
a successful call to ->remove().
Jan
> -----Original Message-----
> From: Jan Beulich <[email protected]>
> Sent: 29 November 2019 11:56
> To: Durrant, Paul <[email protected]>
> Cc: [email protected]; [email protected]; linux-
> [email protected]; Roger Pau Monné <[email protected]>; Jens Axboe
> <[email protected]>; Konrad Rzeszutek Wilk <[email protected]>
> Subject: Re: [PATCH] xen-blkback: allow module to be cleanly unloaded
>
> On 29.11.2019 12:31, Paul Durrant wrote:
> > --- 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);
> > }
>
> I realize there are various example of this in the tree, but
> isn't this a flawed approach? __module_get() (nor even
> try_module_get()) will prevent an unload attempt ahead of it
> getting invoked, while execution is already in this module's
> .text section.
Good point. That does appear to be a race.
> I think the xenbus driver should do this
> before calling ->probe(), in case of its failure, and after
> a successful call to ->remove().
>
That does sound better. I'll see if I can pick up other occurrences (certainly netback) and fix.
Paul