Re: [PATCH v4 8/8] iommu/vt-d: Misc macro clean up for SVM

From: Joe Perches
Date: Mon Dec 02 2019 - 13:23:03 EST


On Mon, 2019-12-02 at 10:15 -0800, Jacob Pan wrote:
> On Thu, 21 Nov 2019 13:37:10 -0800
> Joe Perches <joe@xxxxxxxxxxx> wrote:
>
> > On Thu, 2019-11-21 at 13:26 -0800, Jacob Pan wrote:
> > > Use combined macros for_each_svm_dev() to simplify SVM device
> > > iteration and error checking.
> > []
> > > diff --git a/drivers/iommu/intel-svm.c b/drivers/iommu/intel-svm.c
> > []
> > > +#define for_each_svm_dev(sdev, svm, d) \
> > > + list_for_each_entry((sdev), &(svm)->devs, list) \
> > > + if ((d) != (sdev)->dev) {} else
> > > +
> > > int intel_svm_bind_mm(struct device *dev, int *pasid, int flags,
> > > struct svm_dev_ops *ops) {
> > > struct intel_iommu *iommu = intel_svm_device_to_iommu(dev);
> > > @@ -274,15 +278,13 @@ int intel_svm_bind_mm(struct device *dev, int
> > > *pasid, int flags, struct svm_dev_ goto out;
> > > }
> > >
> > > - list_for_each_entry(sdev, &svm->devs,
> > > list) {
> > > - if (dev == sdev->dev) {
> > > - if (sdev->ops != ops) {
> > > - ret = -EBUSY;
> > > - goto out;
> > > - }
> > > - sdev->users++;
> > > - goto success;
> > > + for_each_svm_dev(sdev, svm, dev) {
> > > + if (sdev->ops != ops) {
> > > + ret = -EBUSY;
> > > + goto out;
> > > }
> > > + sdev->users++;
> > > + goto success;
> > > }
> >
> > I think this does not read better as this is now a
> > for_each loop that exits the loop on the first match.
> >
> I think one of the benefits is reduced indentation. What do you
> recommend?

Making the code intelligible for a reader.

At least add a comment describing why there is only
a single possible match.

Given the for_each name, it's odd code that only the
first match has an action.