Re: [PATCH V2 for-next 7/7] IB/core: Change completion channel to use the reworked objects schema

[Jason Gunthorpe <jgunthorpe-ePGOBjL8dl3ta4EC/59zMFaTQe2KTcn/@public.gmane.org>]

On Wed, Mar 29, 2017 at 09:21:09PM +0300, Matan Barak wrote:
> On Wed, Mar 29, 2017 at 5:53 PM, Jason Gunthorpe
> <jgunthorpe-ePGOBjL8dl3ta4EC/59zMFaTQe2KTcn/@public.gmane.org> wrote:
> > On Sun, Mar 19, 2017 at 05:59:05PM +0200, Matan Barak wrote:
> >> +static struct ib_uverbs_completion_event_file *
> >> +ib_uverbs_lookup_comp_file(int fd, struct ib_ucontext *context)
> >> +{
> >> +     struct ib_uobject *uobj = uobj_get_read(uobj_get_type(comp_channel),
> >> +                                             fd, context);
> >> +     struct ib_uobject_file *uobj_file;
> >> +
> >> +     if (IS_ERR(uobj))
> >> +             return (void *)uobj;
> >> +
> >> +     uobj_file = container_of(uobj, struct ib_uobject_file, uobj);
> >> +
> >> +     uverbs_uobject_get(&uobj_file->uobj);
> >> +     uobj_put_read(uobj);
> >
> > That looks odd, isn't uobj == uobj_file->uobj ?
> 
> Yeah, they're essentially the same. The uverbs_uobject_get is intended
> to increase the reference count
> on the returned object. The uobj_put_read is paired with uobj_get_read
> (first line of this function).
> We could change them both to uobj.

I'm confused why you would ever write

uverbs_uobject_get(uobj);
uobj_put_read(uobj);

Maybe drop both lines and just add a comment that the ref from
uobj_get_read moves from the stack to XX

Jason
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