Re: [PATCH v7 8/8] dmaengine: idxd: fix cdev setup and free device lifetime issues

[Dave Jiang <dave.jiang@intel.com>]

On 3/22/2021 4:38 PM, Dan Williams wrote:
> On Mon, Mar 22, 2021 at 4:32 PM Dave Jiang <dave.jiang@intel.com> wrote:
>> The char device setup and cleanup has device lifetime issues regarding when
>> parts are initialized and cleaned up. The initialization of struct device is
>> done incorrectly. device_initialize() needs to be called on the 'struct
>> device' and then additional changes can be added. The ->release() function
>> needs to be setup via device_type before dev_set_name() to allow proper
>> cleanup. The change re-parents the cdev under the wq->conf_dev to get
>> natural reference inheritance. No known dependency on the old device path exists.
>>
>> Reported-by: Jason Gunthorpe <jgg@nvidia.com>
>> Fixes: 42d279f9137a ("dmaengine: idxd: add char driver to expose submission portal to userland")
>> Signed-off-by: Dave Jiang <dave.jiang@intel.com>
>> Reviewed-by: Dan Williams <dan.j.williams@intel.com>
> [..]
>> diff --git a/drivers/dma/idxd/sysfs.c b/drivers/dma/idxd/sysfs.c
>> index 03079ff54889..8a08988ea9d1 100644
>> --- a/drivers/dma/idxd/sysfs.c
>> +++ b/drivers/dma/idxd/sysfs.c
>> @@ -1174,8 +1174,14 @@ static ssize_t wq_cdev_minor_show(struct device *dev,
>>                                    struct device_attribute *attr, char *buf)
>>   {
>>          struct idxd_wq *wq = container_of(dev, struct idxd_wq, conf_dev);
>> +       int minor = -1;
>>
>> -       return sprintf(buf, "%d\n", wq->idxd_cdev.minor);
>> +       mutex_lock(&wq->wq_lock);
>> +       if (wq->idxd_cdev)
>> +               minor = wq->idxd_cdev->minor;
>> +       mutex_unlock(&wq->wq_lock);
>> +
>> +       return sprintf(buf, "%d\n", minor);
> As I mentioned, let's not emit a negative value here. ...not that
> userspace should be using this awkward recreation of the existing core
> 'dev' attribute anyway.
>
> if (minor == -1)
>      return -ENXIO;
> return sprintf(buf, "%d\n", minor);
Ok I'll update. This will go away when we convert to UACCE based driver.