On Wed, 2024-06-26 at 14:48 +0200, Gerd Bayer wrote:
> Hi Ma Ke,
>
> On Wed, 2024-06-26 at 16:12 +0800, Ma Ke wrote:
> > As the possible failure of the dma_set_max_seg_size(), we should
> > better check the return value of the dma_set_max_seg_size().
>
> I think formally you're correct. dma_set_max_seg_size() could return an
> error if dev->dma_parms was not present.
>
> However, since ISM devices are PCI attached (and will remain PCI
> attached I believe) we can take the existance of dev->dma_parms for
> granted since pci_device_add() (in drivers/pci/probe.c) will make that
> point to the pci_dev's dma_parms for every PCI device.
>
> So I'm not sure how important this fix is.
I agree this doesn't look like an issue we're likely to encounter. That
said if for some reason dma_set_max_seg_size() or common PCI code is
changed and it starts failing it's good to have it handled.
This line has also only been dma_set_max_seg_size() since commit
b0da3498c587 ("PCI: Remove pci_set_dma_max_seg_size()"). Since this
patch won't apply for anything older I would prefer to cite that as the
fixed commit.
>
> > Fixes: 684b89bc39ce ("s390/ism: add device driver for internal shared
> > memory")
> > Signed-off-by: Ma Ke <make24@xxxxxxxxxxx>
> > ---
> > drivers/s390/net/ism_drv.c | 4 +++-
> > 1 file changed, 3 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/s390/net/ism_drv.c b/drivers/s390/net/ism_drv.c
> > index e36e3ea165d3..9ddd093a0368 100644
> > --- a/drivers/s390/net/ism_drv.c
> > +++ b/drivers/s390/net/ism_drv.c
> > @@ -620,7 +620,9 @@ static int ism_probe(struct pci_dev *pdev, const
> > struct pci_device_id *id)
> > goto err_resource;
^ see here
> >
> > dma_set_seg_boundary(&pdev->dev, SZ_1M - 1);
> > - dma_set_max_seg_size(&pdev->dev, SZ_1M);
> > + ret = dma_set_max_seg_size(&pdev->dev, SZ_1M);
> > + if (ret)
> > + return ret;
Simply returning here would leak the resources. Just like the error
condition I marked above this would need to be goto err_resource.
> > pci_set_master(pdev);
> >
> > ret = ism_dev_init(ism);
>
> BTW, I've dropped ubraun@xxxxxxxxxxxxx and sebott@xxxxxxxxxxxxx as
> their emails won't work any longer, anyhow. Instead I've added Niklas
> Schnelle, Wenjia Zhang and Stefan Raspl.
>
> Thanks, Gerd
>
