netdev - Re: [RFC PATCH v4 01/25] virtual-bus: Implementation of Virtual Bus

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Date:   Fri, 14 Feb 2020 15:43:41 -0500
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Jason Gunthorpe <jgg@...pe.ca>
Cc:     Jeff Kirsher <jeffrey.t.kirsher@...el.com>, davem@...emloft.net,
        Dave Ertman <david.m.ertman@...el.com>, netdev@...r.kernel.org,
        linux-rdma@...r.kernel.org, nhorman@...hat.com,
        sassmann@...hat.com, parav@...lanox.com, galpress@...zon.com,
        selvin.xavier@...adcom.com, sriharsha.basavapatna@...adcom.com,
        benve@...co.com, bharat@...lsio.com, xavier.huwei@...wei.com,
        yishaih@...lanox.com, leonro@...lanox.com, mkalderon@...vell.com,
        aditr@...are.com, Kiran Patil <kiran.patil@...el.com>,
        Andrew Bowers <andrewx.bowers@...el.com>
Subject: Re: [RFC PATCH v4 01/25] virtual-bus: Implementation of Virtual Bus

On Fri, Feb 14, 2020 at 04:34:55PM -0400, Jason Gunthorpe wrote:
> On Fri, Feb 14, 2020 at 09:02:40AM -0800, Greg KH wrote:
> > > +/**
> > > + * virtbus_dev_register - add a virtual bus device
> > > + * @vdev: virtual bus device to add
> > > + */
> > > +int virtbus_dev_register(struct virtbus_device *vdev)
> > > +{
> > > +	int ret;
> > > +
> > > +	if (!vdev->release) {
> > > +		dev_err(&vdev->dev, "virtbus_device .release callback NULL\n");
> > 
> > "virtbus_device MUST have a .release callback that does something!\n" 
> > 
> > > +		return -EINVAL;
> > > +	}
> > > +
> > > +	device_initialize(&vdev->dev);
> > > +
> > > +	vdev->dev.bus = &virtual_bus_type;
> > > +	vdev->dev.release = virtbus_dev_release;
> > > +	/* All device IDs are automatically allocated */
> > > +	ret = ida_simple_get(&virtbus_dev_ida, 0, 0, GFP_KERNEL);
> > > +	if (ret < 0) {
> > > +		dev_err(&vdev->dev, "get IDA idx for virtbus device failed!\n");
> > > +		put_device(&vdev->dev);
> > 
> > If you allocate the number before device_initialize(), no need to call
> > put_device().  Just a minor thing, no big deal.
> 
> If *_regster does put_device on error then it must always do
> put_device on any error, for instance the above return -EINVAL with
> no put_device leaks memory.

That's why I said to move the ida_simple_get() call to before
device_initialize() is called.  Once device_initialize() is called, you
HAVE to call put_device().

Just trying to make code smaller :)

greg k-h