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From: John Hubbard <jhubbard@nvidia.com>
To: Minchan Kim <minchan@kernel.org>, Greg KH <gregkh@linuxfoundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>,
	linux-mm <linux-mm@kvack.org>,
	LKML <linux-kernel@vger.kernel.org>, <surenb@google.com>,
	<joaodias@google.com>, <willy@infradead.org>
Subject: Re: [PATCH v2] mm: cma: support sysfs
Date: Tue, 9 Feb 2021 23:16:07 -0800	[thread overview]
Message-ID: <e7ea55b9-a5f6-0daf-843b-e25d8c70e980@nvidia.com> (raw)
In-Reply-To: <YCOHRAAijtCbN+pr@google.com>

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


  reply	other threads:[~2021-02-10  7:16 UTC|newest]

Thread overview: 20+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-02-08 18:01 [PATCH v2] mm: cma: support sysfs Minchan Kim
2021-02-08 21:34 ` John Hubbard
2021-02-08 23:36   ` Minchan Kim
2021-02-09  1:57     ` John Hubbard
2021-02-09  4:19       ` Minchan Kim
2021-02-09  5:18         ` John Hubbard
2021-02-09  5:27           ` John Hubbard
2021-02-09  6:13       ` Greg KH
2021-02-09  6:27         ` John Hubbard
2021-02-09  6:34           ` John Hubbard
2021-02-09  6:56             ` Greg KH
2021-02-09 15:55               ` Minchan Kim
2021-02-09 17:49                 ` Greg KH
2021-02-09 20:11                   ` John Hubbard
2021-02-09 21:13                     ` Minchan Kim
2021-02-10  6:43                       ` Greg KH
2021-02-10  7:12                         ` Minchan Kim
2021-02-10  7:16                           ` John Hubbard [this message]
2021-02-10  7:26                             ` Greg KH
2021-02-10  7:50                               ` John Hubbard

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