Re: [PATCH v2] mm: cma: support sysfs

[John Hubbard]

On 2/9/21 11:12 PM, Minchan Kim wrote:
...
> > > Agreed. How about this for the warning part?
> > >
> > > +
> > > +/*
> > > + * note: kobj_type should provide a release function to free dynamically
> > > + * allocated object since kobject is responsible for controlling lifespan
> > > + * of the object. However, cma_area is static object so technially, it
> > > + * doesn't need release function. It's very exceptional case so pleaes
> > > + * do not follow this model.
> > > + */
> > >   static struct kobj_type cma_ktype = {
> > >          .sysfs_ops = &kobj_sysfs_ops,
> > >          .default_groups = cma_groups
> > > +       .release = NULL, /* do not follow. See above */
> > >   };
> >
> > No, please no.  Just do it the correct way, what is the objection to
> > creating a few dynamic kobjects from the heap?  How many of these are
> > you going to have that it will somehow be "wasteful"?
> >
> > Please do it properly.
>
> Oh, I misunderstood your word "don't provide a release function for the
> kobject" so thought you agreed on John. If you didn't, we are stuck again:
> IIUC, the objection from John was the cma_stat lifetime should be on parent
> object, which is reasonable and make code simple.
> Frankly speaking, I don't have strong opinion about either approach.
> John?

We should do it as Greg requests, now that it's quite clear that he's insisting
on this. Not a big deal.

I just am not especially happy about the inability to do natural, efficient
things here, such as use a statically allocated set of things with sysfs. And
I remain convinced that the above is not "improper"; it's a reasonable
step, given the limitations of the current sysfs design. I just wanted to say
that out loud, as my proposal sinks to the bottom of the trench here. haha :)


thanks,
--
John Hubbard
NVIDIA