[PATCH] virtio: release virtio index when fail to device_register

weiping zhang
Fri, 01 Dec 2017 17:30:13 -0000

2017-12-02 0:55 GMT+08:00 weiping zhang <zwp10758 at
gmail.com>:
> On Wed, Nov 29, 2017 at 10:50:44AM +0100, Cornelia Huck wrote:
>> On Wed, 29 Nov 2017 09:23:01 +0800
>> weiping zhang <zwp10758 at gmail.com> wrote:
>>
>> > index can be reused by other virtio device.
>> >
>> > Signed-off-by: weiping zhang <zhangweiping at
didichuxing.com>
>>
>> Reviewed-by: Cornelia Huck <cohuck at redhat.com>
>>
>> > ---
>> >  drivers/virtio/virtio.c | 2 ++
>> >  1 file changed, 2 insertions(+)
>> >
>> > diff --git a/drivers/virtio/virtio.c b/drivers/virtio/virtio.c
>> > index 48230a5..bf7ff39 100644
>> > --- a/drivers/virtio/virtio.c
>> > +++ b/drivers/virtio/virtio.c
>> > @@ -333,6 +333,8 @@ int register_virtio_device(struct
virtio_device *dev)
>> >     /* device_register() causes the bus infrastructure to look for
a
>> >      * matching driver. */
>> >     err = device_register(&dev->dev);
>> > +   if (err)
>> > +           ida_simple_remove(&virtio_index_ida,
dev->index);
>> >  out:
>> >     if (err)
>> >             virtio_add_status(dev, VIRTIO_CONFIG_S_FAILED);
>>
>> I think your patch is correct (giving up the index if we failed to
>> register), but this made me look at our error handling if a virtio
>> device failed to register.
>>
>> We hold an extra reference to the struct device, even after a failed
>> register, and it is the responsibility of the caller to give up that
>> reference once no longer needed. As callers toregister_virtio_device()
>> embed the struct virtio_device, it needs to be their responsibility.
>> Looking at the existing callers,
>>
>> - ccw does a put_device
>> - pci, mmio and remoteproc do nothing, causing a leak
>> - vop does a free on the embedding structure, which is a big no-no
>>
>> Thoughts?
> Sorry to relay late and thanks for your review.
> Do you mean the "extra reference to the struct device" caused by
the
> following code?
>
> err = device_register(&dev->dev);
>         device_add(dev)
>                 get_device(dev)
> If I'm understand right, I think there is no extra reference if we fail
> virtio_register_device, because if device_register we don't get a
> reference.

I go through these callers,  virtio_mmio_probe should do more cleanup.
I'll sent a patch fix that.

> --
> Thanks
> weiping