Re: [PATCH v5] Drivers: hv: vmbus: Expose monitor data only when monitor pages are used

From: Kimberly Brown
Date: Mon Mar 11 2019 - 20:05:17 EST


On Sat, Mar 09, 2019 at 08:21:35AM +0100, Greg KH wrote:
> On Fri, Mar 08, 2019 at 05:46:11PM -0500, Kimberly Brown wrote:
> > static struct kobj_type vmbus_chan_ktype = {
> > .sysfs_ops = &vmbus_chan_sysfs_ops,
> > .release = vmbus_chan_release,
> > - .default_attrs = vmbus_chan_attrs,
>
> As discussed on IRC, a kobj_type needs to get an attribute group one of
> these days, not just a attribute list :)
>
> So thanks for persisting with this, sorry for the earlier review
> comments, you were totally right about this, nice work.
>
> Minor review comments below:
>
> > };
> >
> > /*
> > @@ -1571,11 +1624,34 @@ int vmbus_add_channel_kobj(struct hv_device *dev, struct vmbus_channel *channel)
> > if (ret)
> > return ret;
> >
> > + ret = sysfs_create_group(kobj, &vmbus_chan_group);
> > + channel->sysfs_group_ready = !ret;
>
> Why do you need this flag?
>

I added this flag to prevent sysfs_remove_group() from being called if
sysfs_create_group() or the earlier call to kobject_init_and_add()
failed. However, it looks like that would just lead to WARN() being
called, which seems appropriate. I'll remove this flag.


> > +
> > + if (ret) {
> > + /*
> > + * If an error is returned to the calling functions, those
> > + * functions will call kobject_put() on the channel kobject,
> > + * which will cleanup the empty channel directory created by
> > + * kobject_init_and_add().
>
> Why is this comment needed?
>

Another reviewer asked why the empty directory created by
kobject_init_and_add() isn't removed here when sysfs_create_group()
fails. We decided that a comment would help clear up any future
confusion.


> > + */
> > + pr_err("Unable to set up channel sysfs files\n");
>
> dev_err() to show who had the problem with the files?
>

Yes, good point. I'll change this.


> > + return ret;
> > + }
> > +
> > kobject_uevent(kobj, KOBJ_ADD);
> >
> > return 0;
> > }
> >
> > +/*
> > + * vmbus_remove_channel_attr_group - remove the channel's attribute group
> > + */
> > +void vmbus_remove_channel_attr_group(struct vmbus_channel *channel)
> > +{
> > + if (channel->sysfs_group_ready)
> > + sysfs_remove_group(&channel->kobj, &vmbus_chan_group);
>
> You should be able to just always remove these, no need for a flag to
> say you have created them or not, right?
>
> thanks,
>
> greg k-h