linux-kernel - Re: [PATCH v2] mm: cma: support sysfs

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Message-ID: <3cf67381-9b5a-56ee-2a8f-047955c84128@nvidia.com>
Date:   Mon, 8 Feb 2021 21:18:52 -0800
From:   John Hubbard <jhubbard@...dia.com>
To:     Minchan Kim <minchan@...nel.org>
CC:     Andrew Morton <akpm@...ux-foundation.org>,
        linux-mm <linux-mm@...ck.org>,
        LKML <linux-kernel@...r.kernel.org>,
        <gregkh@...uxfoundation.org>, <surenb@...gle.com>,
        <joaodias@...gle.com>, <willy@...radead.org>
Subject: Re: [PATCH v2] mm: cma: support sysfs

On 2/8/21 8:19 PM, Minchan Kim wrote:
> On Mon, Feb 08, 2021 at 05:57:17PM -0800, John Hubbard wrote:
>> On 2/8/21 3:36 PM, Minchan Kim wrote:
>> ...
>>>>>     	char name[CMA_MAX_NAME];
>>>>> +#ifdef CONFIG_CMA_SYSFS
>>>>> +	struct cma_stat	*stat;
>>>>
>>>> This should not be a pointer. By making it a pointer, you've added a bunch of pointless
>>>> extra code to the implementation.
>>>
>>> Originally, I went with the object lifetime with struct cma as you
>>> suggested to make code simple. However, Greg KH wanted to have
>>> release for kobj_type since it is consistent with other kboject
>>> handling.
>>
>> Are you talking about the kobj in your new struct cma_stat? That seems
>> like circular logic if so. I'm guessing Greg just wanted kobj methods
>> to be used *if* you are dealing with kobjects. That's a narrower point.
>>
>> I can't imagine that he would have insisted on having additional
>> allocations just so that kobj freeing methods could be used. :)
> 
> I have no objection if Greg agree static kobject is okay in this
> case. Greg?
> 

What I meant is, no kobject at all in the struct cma_stat member
variable. The lifetime of the cma_stat member is the same as the
containing struct, so no point in putting a kobject into it.

thanks,
-- 
John Hubbard
NVIDIA