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From: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Date: Thu, 11 Oct 2012 18:33:23 -0400
Message-ID: <CAHGf_=rvdU+TymYZSXvx1bz4xdp43bqnyjRMGEoiBizC5rP0sQ@mail.gmail.com>
Subject: Re: [PATCH 2/2]suppress "Device nodeX does not have a release()
 function" warning
To: Yasuaki Ishimatsu <isimatu.yasuaki@jp.fujitsu.com>
Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, rientjes@google.com,
        liuj97@gmail.com, minchan.kim@gmail.com, akpm@linux-foundation.org,
        wency@cn.fujitsu.com
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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.


>  /*
>   * 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.
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