Re: [PATCH v5 2/3] vfio: Export the device set open count

[Alex Williamson <alex.williamson@redhat.com>]

On Tue, 8 Nov 2022 20:48:08 -0400
Jason Gunthorpe <jgg@ziepe.ca> wrote:

> On Sat, Nov 05, 2022 at 03:44:57PM -0700, Anthony DeRossi wrote:
> > The open count of a device set is the sum of the open counts of all
> > devices in the set. Drivers can use this value to determine whether
> > shared resources are in use without tracking them manually or accessing
> > the private open_count in vfio_device.
> > 
> > Signed-off-by: Anthony DeRossi <ajderossi@gmail.com>
> > ---
> >  drivers/vfio/vfio_main.c | 11 +++++++++++
> >  include/linux/vfio.h     |  1 +
> >  2 files changed, 12 insertions(+)  
> 
> >  
> > +unsigned int vfio_device_set_open_count(struct vfio_device_set *dev_set)
> > +{
> > +	struct vfio_device *cur;
> > +	unsigned int open_count = 0;  
> 
> I'd probably just make this a bool
> 
> 'vfio_device_set_last_close()'
> 
> And roll in the < 1 logic too
> 
> Nothing will ever need to know the number of fds open across the set.

'last_close' presumes the caller though, which seems bad form.  It's
possible there are use cases for this in a 'first_open' scenario too.
Something along the lines of 'singleton_open', but that's a horrible
name, so we might as well just provide the count since we already have
it.  Thanks,

Alex

> But this is fine as written
> 
> Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
> 
> Jason
>