Paul Durrant (2):
xen/xenbus: reference count registered modules
block/xen-blkback: allow module to be cleanly unloaded
drivers/block/xen-blkback/blkback.c | 8 ++++++++
drivers/block/xen-blkback/common.h | 3 +++
drivers/block/xen-blkback/xenbus.c | 11 +++++++++++
drivers/xen/xenbus/xenbus_probe.c | 8 +++++++-
4 files changed, 29 insertions(+), 1 deletion(-)
--
2.20.1
Add a module_exit() to perform the necessary clean-up.
Signed-off-by: Paul Durrant <[email protected]>
---
Cc: Konrad Rzeszutek Wilk <[email protected]>
Cc: "Roger Pau Monné" <[email protected]>
Cc: Jens Axboe <[email protected]>
v2:
- Drop the addition of ad-hoc reference counting as this is now done
centrally in xenbus
---
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
To prevent a module being removed whilst attached to a frontend, 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.
NOTE: This allows the ad-hoc reference counting in xen-netback to be
removed. This will be done in a subsequent patch.
Suggested-by: Jan Beulich <[email protected]>
Signed-off-by: Paul Durrant <[email protected]>
---
Cc: Boris Ostrovsky <[email protected]>
Cc: Juergen Gross <[email protected]>
Cc: Stefano Stabellini <[email protected]>
v2:
- New in v2
---
drivers/xen/xenbus/xenbus_probe.c | 8 +++++++-
1 file changed, 7 insertions(+), 1 deletion(-)
diff --git a/drivers/xen/xenbus/xenbus_probe.c b/drivers/xen/xenbus/xenbus_probe.c
index 5b471889d723..5a4947690500 100644
--- a/drivers/xen/xenbus/xenbus_probe.c
+++ b/drivers/xen/xenbus/xenbus_probe.c
@@ -232,9 +232,11 @@ int xenbus_dev_probe(struct device *_dev)
return err;
}
+ __module_get(drv->driver.owner);
+
err = drv->probe(dev, id);
if (err)
- goto fail;
+ goto fail_put;
err = watch_otherend(dev);
if (err) {
@@ -244,6 +246,8 @@ 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 +267,8 @@ 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
> -----Original Message-----
> From: Roger Pau Monn? <[email protected]>
> Sent: 29 November 2019 15:00
> To: Durrant, Paul <[email protected]>
> Cc: [email protected]; [email protected]; xen-
> [email protected]; Konrad Rzeszutek Wilk
> <[email protected]>; Jens Axboe <[email protected]>
> Subject: Re: [PATCH v2 2/2] block/xen-blkback: allow module to be cleanly
> unloaded
>
> On Fri, Nov 29, 2019 at 01:43:06PM +0000, Paul Durrant wrote:
> > Add a module_exit() to perform the necessary clean-up.
> >
> > Signed-off-by: Paul Durrant <[email protected]>
>
> LGTM:
>
> Reviewed-by: Roger Pau Monn? <[email protected]>
>
Thanks.
> AFAICT we should make sure this is not committed before patch 1, or
> else you could unload a blkback module that's still in use?
>
Yes, that's correct.
Paul
On Fri, Nov 29, 2019 at 01:43:06PM +0000, Paul Durrant wrote:
> Add a module_exit() to perform the necessary clean-up.
>
> Signed-off-by: Paul Durrant <[email protected]>
LGTM:
Reviewed-by: Roger Pau Monn? <[email protected]>
AFAICT we should make sure this is not committed before patch 1, or
else you could unload a blkback module that's still in use?
Thanks, Roger.
On Fri, Nov 29, 2019 at 03:02:37PM +0000, Durrant, Paul wrote:
> > -----Original Message-----
> > From: Roger Pau Monn? <[email protected]>
> > Sent: 29 November 2019 15:00
> > To: Durrant, Paul <[email protected]>
> > Cc: [email protected]; [email protected]; xen-
> > [email protected]; Konrad Rzeszutek Wilk
> > <[email protected]>; Jens Axboe <[email protected]>
> > Subject: Re: [PATCH v2 2/2] block/xen-blkback: allow module to be cleanly
> > unloaded
> >
> > On Fri, Nov 29, 2019 at 01:43:06PM +0000, Paul Durrant wrote:
> > > Add a module_exit() to perform the necessary clean-up.
> > >
> > > Signed-off-by: Paul Durrant <[email protected]>
> >
> > LGTM:
> >
> > Reviewed-by: Roger Pau Monn? <[email protected]>
> >
>
> Thanks.
>
> > AFAICT we should make sure this is not committed before patch 1, or
> > else you could unload a blkback module that's still in use?
> >
>
> Yes, that's correct.
Given this is a very small change, and not really block related I
think it would be better for both patches to be committed from the Xen
tree, if Jens, Juergen and Boris agree.
Thanks, Roger.
On 29.11.19 16:07, Roger Pau Monné wrote:
> On Fri, Nov 29, 2019 at 03:02:37PM +0000, Durrant, Paul wrote:
>>> -----Original Message-----
>>> From: Roger Pau Monné <[email protected]>
>>> Sent: 29 November 2019 15:00
>>> To: Durrant, Paul <[email protected]>
>>> Cc: [email protected]; [email protected]; xen-
>>> [email protected]; Konrad Rzeszutek Wilk
>>> <[email protected]>; Jens Axboe <[email protected]>
>>> Subject: Re: [PATCH v2 2/2] block/xen-blkback: allow module to be cleanly
>>> unloaded
>>>
>>> On Fri, Nov 29, 2019 at 01:43:06PM +0000, Paul Durrant wrote:
>>>> Add a module_exit() to perform the necessary clean-up.
>>>>
>>>> Signed-off-by: Paul Durrant <[email protected]>
>>>
>>> LGTM:
>>>
>>> Reviewed-by: Roger Pau Monné <[email protected]>
>>>
>>
>> Thanks.
>>
>>> AFAICT we should make sure this is not committed before patch 1, or
>>> else you could unload a blkback module that's still in use?
>>>
>>
>> Yes, that's correct.
>
> Given this is a very small change, and not really block related I
> think it would be better for both patches to be committed from the Xen
> tree, if Jens, Juergen and Boris agree.
I'm fine with that.
And:
Reviewed-by: Juergen Gross <[email protected]>
Juergen
On 29.11.19 14:43, Paul Durrant wrote:
> To prevent a module being removed whilst attached to a frontend, 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.
>
> NOTE: This allows the ad-hoc reference counting in xen-netback to be
> removed. This will be done in a subsequent patch.
>
> Suggested-by: Jan Beulich <[email protected]>
> Signed-off-by: Paul Durrant <[email protected]>
Reviewed-by: Juergen Gross <[email protected]>
Juergen
On 29.11.2019 14:43, Paul Durrant wrote:
> To prevent a module being removed whilst attached to a frontend, and
Why only frontend?
> 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.
>
> NOTE: This allows the ad-hoc reference counting in xen-netback to be
> removed. This will be done in a subsequent patch.
>
> Suggested-by: Jan Beulich <[email protected]>
> Signed-off-by: Paul Durrant <[email protected]>
>
> --- a/drivers/xen/xenbus/xenbus_probe.c
> +++ b/drivers/xen/xenbus/xenbus_probe.c
> @@ -232,9 +232,11 @@ int xenbus_dev_probe(struct device *_dev)
> return err;
> }
>
> + __module_get(drv->driver.owner);
I guess you really want try_module_get() and deal with it returning
false.
Jan
> -----Original Message-----
> From: Jan Beulich <[email protected]>
> Sent: 29 November 2019 16:01
> To: Durrant, Paul <[email protected]>
> Cc: [email protected]; [email protected]; linux-
> [email protected]; Stefano Stabellini <[email protected]>; Boris
> Ostrovsky <[email protected]>; Juergen Gross <[email protected]>
> Subject: Re: [PATCH v2 1/2] xen/xenbus: reference count registered modules
>
> On 29.11.2019 14:43, Paul Durrant wrote:
> > To prevent a module being removed whilst attached to a frontend, and
>
> Why only frontend?
>
True. Originally this was only intended for backends, but I guess this should now be 'otherend' or some equivalent form of words.
> > 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.
> >
> > NOTE: This allows the ad-hoc reference counting in xen-netback to be
> > removed. This will be done in a subsequent patch.
> >
> > Suggested-by: Jan Beulich <[email protected]>
> > Signed-off-by: Paul Durrant <[email protected]>
> >
> > --- a/drivers/xen/xenbus/xenbus_probe.c
> > +++ b/drivers/xen/xenbus/xenbus_probe.c
> > @@ -232,9 +232,11 @@ int xenbus_dev_probe(struct device *_dev)
> > return err;
> > }
> >
> > + __module_get(drv->driver.owner);
>
> I guess you really want try_module_get() and deal with it returning
> false.
>
Perhaps, yes.
Paul
> Jan