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 5:02 PM, Jason Gunthorpe wrote:
> On Mon, Mar 22, 2021 at 04:44:24PM -0700, Dave Jiang wrote:
>> 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
>>>> +++ 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.
> Also ensure all new syfs callbacks are using sysfs_emit()
>
Thanks Jason! I have posted a patch that fixes all the instances [1]. 
But I can fix it locally here as well.


[1]: 
https://lore.kernel.org/dmaengine/161495936863.573579.5804720281778882171.stgit@djiang5-desk3.ch.intel.com/