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

John Hubbard
2021-02-10T07:17:08Z

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