On Mon, 11 Oct 2021 16:33:45 +0200
Cornelia Huck <cohuck@xxxxxxxxxx> wrote:
> On Mon, Oct 11 2021, Pierre Morel <pmorel@xxxxxxxxxxxxx> wrote:
>
> > On 10/11/21 1:59 PM, Halil Pasic wrote:
> >> diff --git a/drivers/s390/cio/device_ops.c b/drivers/s390/cio/device_ops.c
> >> index 0fe7b2f2e7f5..c533d1dadc6b 100644
> >> --- a/drivers/s390/cio/device_ops.c
> >> +++ b/drivers/s390/cio/device_ops.c
> >> @@ -825,13 +825,23 @@ EXPORT_SYMBOL_GPL(ccw_device_get_chid);
> >> */
> >> void *ccw_device_dma_zalloc(struct ccw_device *cdev, size_t size)
> >> {
> >> - return cio_gp_dma_zalloc(cdev->private->dma_pool, &cdev->dev, size);
> >> + void *addr;
> >> +
> >> + if (!get_device(&cdev->dev))
> >> + return NULL;
> >> + addr = cio_gp_dma_zalloc(cdev->private->dma_pool, &cdev->dev, size);
> >> + if (IS_ERR_OR_NULL(addr))
> >
> > I can be wrong but it seems that only dma_alloc_coherent() used in
> > cio_gp_dma_zalloc() report an error but the error is ignored and used as
> > a valid pointer.
>
> Hm, I thought dma_alloc_coherent() returned either NULL or a valid
> address?
Yes, that is what is documented.
>
> >
> > So shouldn't we modify this function and just test for a NULL address here?
>
> If I read cio_gp_dma_zalloc() correctly, we either get NULL or a valid
> address, so yes.
>
I don't think the extra care will hurt us too badly. I prefer to keep
the IS_ERR_OR_NULL() check because it needs less domain specific
knowledge to be understood, and because it is more robust.
Regards,
Halil
