Re: [RFC v1 7/8] mshv: implement in-kernel device framework

From: Matthew Wilcox
Date: Fri Jul 09 2021 - 11:33:01 EST


On Fri, Jul 09, 2021 at 01:50:13PM +0000, Wei Liu wrote:
> On Fri, Jul 09, 2021 at 02:02:04PM +0100, Matthew Wilcox wrote:
> > On Fri, Jul 09, 2021 at 11:43:38AM +0000, Wei Liu wrote:
> > > +static long
> > > +mshv_partition_ioctl_create_device(struct mshv_partition *partition,
> > > + void __user *user_args)
> > > +{
> > [...]
> > > + mshv_partition_get(partition);
> > > + r = anon_inode_getfd(ops->name, &mshv_device_fops, dev, O_RDWR | O_CLOEXEC);
> > > + if (r < 0) {
> > > + mshv_partition_put_no_destroy(partition);
> > > + list_del(&dev->partition_node);
> > > + ops->destroy(dev);
> > > + goto out;
> > > + }
> > > +
> > > + cd->fd = r;
> > > + r = 0;
> >
> > Why return the fd in memory instead of returning the fd as the return
> > value from the ioctl?
> >
> > > + if (copy_to_user(user_args, &tmp, sizeof(tmp))) {
> > > + r = -EFAULT;
> > > + goto out;
> > > + }
> >
> > ... this could then disappear.
>
> Thanks for your comment, Matthew.
>
> This is intentionally because I didn't want to deviate from KVM's API.
> The fewer differences the better.

Then don't define your own structure. Use theirs.