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

[Wen Congyang <wency@cn.fujitsu.com>]

At 10/12/2012 06:33 AM, KOSAKI Motohiro Wrote:
> On Thu, Oct 11, 2012 at 1:26 AM, Yasuaki Ishimatsu
> <isimatu.yasuaki@jp.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@google.com>
>> CC: Jiang Liu <liuj97@gmail.com>
>> Cc: Minchan Kim <minchan.kim@gmail.com>
>> CC: Andrew Morton <akpm@linux-foundation.org>
>> CC: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
>> Signed-off-by: Yasuaki Ishimatsu <isimatu.yasuaki@jp.fujitsu.com>
>> Signed-off-by: Wen Congyang <wency@cn.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.

Thanks
Wen Congyang

> 
> 
>>  /*
>>   * register_node - Setup a sysfs device for a node.
>> @@ -263,8 +271,11 @@ int register_node(struct node *node, int
>>  {
>>         int error;
>>
>> +       memset(node, 0, sizeof(*node));
>> +
> 
> You should add a comment why we need initialize a node here. A lot
> of developers don't have hotplug knowledge.
>