linux-kernel - Re: [PATCH 2/2]suppress "Device nodeX does not have a release() function" warning

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Message-ID: <CAHGf_=obXYBGg9HK6d7AyAe7rjM_NyE6icr69aH-DNOp4tB+VA@mail.gmail.com>
Date:	Wed, 17 Oct 2012 04:50:40 -0400
From:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
To:	Wen Congyang <wency@...fujitsu.com>
Cc:	Yasuaki Ishimatsu <isimatu.yasuaki@...fujitsu.com>,
	linux-mm@...ck.org, linux-kernel@...r.kernel.org,
	rientjes@...gle.com, liuj97@...il.com, minchan.kim@...il.com,
	akpm@...ux-foundation.org
Subject: Re: [PATCH 2/2]suppress "Device nodeX does not have a release()
 function" warning

On Wed, Oct 17, 2012 at 2:24 AM, Wen Congyang <wency@...fujitsu.com> wrote:
> At 10/12/2012 06:33 AM, KOSAKI Motohiro Wrote:
>> On Thu, Oct 11, 2012 at 1:26 AM, Yasuaki Ishimatsu
>> <isimatu.yasuaki@...fujitsu.com> wrote:
>>> When calling unregister_node(), the function shows following message at
>>> device_release().
>>>
>>> "Device 'node2' does not have a release() function, it is broken and must
>>> be fixed."
>>>
>>> The reason is node's device struct does not have a release() function.
>>>
>>> So the patch registers node_device_release() to the device's release()
>>> function for suppressing the warning message. Additionally, the patch adds
>>> memset() to initialize a node struct into register_node(). Because the node
>>> struct is part of node_devices[] array and it cannot be freed by
>>> node_device_release(). So if system reuses the node struct, it has a garbage.
>>>
>>> CC: David Rientjes <rientjes@...gle.com>
>>> CC: Jiang Liu <liuj97@...il.com>
>>> Cc: Minchan Kim <minchan.kim@...il.com>
>>> CC: Andrew Morton <akpm@...ux-foundation.org>
>>> CC: KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
>>> Signed-off-by: Yasuaki Ishimatsu <isimatu.yasuaki@...fujitsu.com>
>>> Signed-off-by: Wen Congyang <wency@...fujitsu.com>
>>> ---
>>>  drivers/base/node.c |   11 +++++++++++
>>>  1 file changed, 11 insertions(+)
>>>
>>> Index: linux-3.6/drivers/base/node.c
>>> ===================================================================
>>> --- linux-3.6.orig/drivers/base/node.c  2012-10-11 10:04:02.149758748 +0900
>>> +++ linux-3.6/drivers/base/node.c       2012-10-11 10:20:34.111806931 +0900
>>> @@ -252,6 +252,14 @@ static inline void hugetlb_register_node
>>>  static inline void hugetlb_unregister_node(struct node *node) {}
>>>  #endif
>>>
>>> +static void node_device_release(struct device *dev)
>>> +{
>>> +#if defined(CONFIG_MEMORY_HOTPLUG_SPARSE) && defined(CONFIG_HUGETLBFS)
>>> +       struct node *node_dev = to_node(dev);
>>> +
>>> +       flush_work(&node_dev->node_work);
>>> +#endif
>>> +}
>>
>> The patch description don't explain why this flush_work() is needed.
>
> If the node is onlined after it is offlined, we will clear the memory,
> so we should flush_work() before node_dev is set to 0.

So then, it is irrelevant from warning supressness. You should make an
another patch.
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