* [PATCH v3 1/2] xen/xenbus: reference count registered modules
2019-12-02 11:41 [PATCH v3 0/2] allow xen-blkback to be cleanly unloaded Paul Durrant
@ 2019-12-02 11:41 ` Paul Durrant
2019-12-03 9:47 ` Jan Beulich
2019-12-04 10:36 ` Jürgen Groß
2019-12-02 11:41 ` [PATCH v3 2/2] xen-blkback: allow module to be cleanly unloaded Paul Durrant
1 sibling, 2 replies; 6+ messages in thread
From: Paul Durrant @ 2019-12-02 11:41 UTC (permalink / raw)
To: linux-block, linux-kernel, xen-devel
Cc: Paul Durrant, Jan Beulich, Boris Ostrovsky, Juergen Gross,
Stefano Stabellini
To prevent a PV driver module being removed whilst attached to its other
end, and hence xenbus calling into potentially invalid text, take a
reference on the module before calling the probe() method (dropping it if
unsuccessful) and drop the reference after returning from the remove()
method.
Suggested-by: Jan Beulich <jbeulich@suse.com>
Signed-off-by: Paul Durrant <pdurrant@amazon.com>
---
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: Juergen Gross <jgross@suse.com>
Cc: Stefano Stabellini <sstabellini@kernel.org>
v2:
- New in v2
v3:
- Use try_module_get() rather than __module)get() and handle failure
- Not added Juergen's R-b because of the change
---
drivers/xen/xenbus/xenbus_probe.c | 13 ++++++++++++-
1 file changed, 12 insertions(+), 1 deletion(-)
diff --git a/drivers/xen/xenbus/xenbus_probe.c b/drivers/xen/xenbus/xenbus_probe.c
index 5b471889d723..4461f4583476 100644
--- a/drivers/xen/xenbus/xenbus_probe.c
+++ b/drivers/xen/xenbus/xenbus_probe.c
@@ -232,9 +232,16 @@ int xenbus_dev_probe(struct device *_dev)
return err;
}
+ if (!try_module_get(drv->driver.owner)) {
+ dev_warn(&dev->dev, "failed to acquire module reference on '%s'.\n",
+ drv->driver.name);
+ err = -ESRCH;
+ goto fail;
+ }
+
err = drv->probe(dev, id);
if (err)
- goto fail;
+ goto fail_put;
err = watch_otherend(dev);
if (err) {
@@ -244,6 +251,8 @@ int xenbus_dev_probe(struct device *_dev)
}
return 0;
+fail_put:
+ module_put(drv->driver.owner);
fail:
xenbus_dev_error(dev, err, "xenbus_dev_probe on %s", dev->nodename);
xenbus_switch_state(dev, XenbusStateClosed);
@@ -263,6 +272,8 @@ int xenbus_dev_remove(struct device *_dev)
if (drv->remove)
drv->remove(dev);
+ module_put(drv->driver.owner);
+
free_otherend_details(dev);
xenbus_switch_state(dev, XenbusStateClosed);
--
2.20.1
^ permalink raw reply related [flat|nested] 6+ messages in thread* [PATCH v3 2/2] xen-blkback: allow module to be cleanly unloaded
2019-12-02 11:41 [PATCH v3 0/2] allow xen-blkback to be cleanly unloaded Paul Durrant
2019-12-02 11:41 ` [PATCH v3 1/2] xen/xenbus: reference count registered modules Paul Durrant
@ 2019-12-02 11:41 ` Paul Durrant
2019-12-04 10:36 ` Jürgen Groß
1 sibling, 1 reply; 6+ messages in thread
From: Paul Durrant @ 2019-12-02 11:41 UTC (permalink / raw)
To: linux-block, linux-kernel, xen-devel
Cc: Paul Durrant, Roger Pau Monné,
Juergen Gross, Konrad Rzeszutek Wilk, Jens Axboe
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>
---
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Paul Durrant <pdurrant@amazon.com>
---
drivers/block/xen-blkback/blkback.c | 8 ++++++++
drivers/block/xen-blkback/common.h | 3 +++
drivers/block/xen-blkback/xenbus.c | 11 +++++++++++
3 files changed, 22 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..e8c5c54e1d26 100644
--- a/drivers/block/xen-blkback/xenbus.c
+++ b/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);
+}
--
2.20.1
^ permalink raw reply related [flat|nested] 6+ messages in thread