From mboxrd@z Thu Jan  1 00:00:00 1970
From: Jaegeuk Hanse <jaegeuk.hanse@gmail.com>
Date: Tue, 20 Nov 2012 06:22:28 +0000
Subject: Re: [PATCH v3 06/12] memory-hotplug: unregister memory section on SPARSEMEM_VMEMMAP
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References: <1351763083-7905-1-git-send-email-wency@cn.fujitsu.com> <1351763083-7905-7-git-send-email-wency@cn.fujitsu.com>
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To: Wen Congyang <wency@cn.fujitsu.com>
Cc: x86@kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-acpi@vger.kernel.org, linux-s390@vger.kernel.org, linux-sh@vger.kernel.org, linux-ia64@vger.kernel.org, cmetcalf@tilera.com, sparclinux@vger.kernel.org, David Rientjes <rientjes@google.com>, Jiang Liu <liuj97@gmail.com>, Len Brown <len.brown@intel.com>, benh@kernel.crashing.org, paulus@samba.org, Christoph Lameter <cl@linux.com>, Minchan Kim <minchan.kim@gmail.com>, Andrew Morton <akpm@linux-foundation.org>, KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>, Yasuaki Ishimatsu <isimatu.yasuaki@jp.fujitsu.com>, Jianguo Wu <wujianguo@huawei.com>

On 11/01/2012 05:44 PM, Wen Congyang wrote:
> From: Yasuaki Ishimatsu <isimatu.yasuaki@jp.fujitsu.com>
>
> Currently __remove_section for SPARSEMEM_VMEMMAP does nothing. But even if
> we use SPARSEMEM_VMEMMAP, we can unregister the memory_section.
>
> So the patch add unregister_memory_section() into __remove_section().

Hi Yasuaki,

In order to review this patch, I should dig sparse memory codes in 
advance. But I have some confuse of codes. Why need encode/decode mem 
map instead of set mem_map to ms->section_mem_map directly?

Regards,
Jaegeuk

>
> CC: David Rientjes <rientjes@google.com>
> CC: Jiang Liu <liuj97@gmail.com>
> CC: Len Brown <len.brown@intel.com>
> CC: Christoph Lameter <cl@linux.com>
> Cc: Minchan Kim <minchan.kim@gmail.com>
> CC: Andrew Morton <akpm@linux-foundation.org>
> CC: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
> CC: Wen Congyang <wency@cn.fujitsu.com>
> Signed-off-by: Yasuaki Ishimatsu <isimatu.yasuaki@jp.fujitsu.com>
> ---
>   mm/memory_hotplug.c | 13 ++++++++-----
>   1 file changed, 8 insertions(+), 5 deletions(-)
>
> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
> index ca07433..66a79a7 100644
> --- a/mm/memory_hotplug.c
> +++ b/mm/memory_hotplug.c
> @@ -286,11 +286,14 @@ static int __meminit __add_section(int nid, struct zone *zone,
>   #ifdef CONFIG_SPARSEMEM_VMEMMAP
>   static int __remove_section(struct zone *zone, struct mem_section *ms)
>   {
> -	/*
> -	 * XXX: Freeing memmap with vmemmap is not implement yet.
> -	 *      This should be removed later.
> -	 */
> -	return -EBUSY;
> +	int ret = -EINVAL;
> +
> +	if (!valid_section(ms))
> +		return ret;
> +
> +	ret = unregister_memory_section(ms);
> +
> +	return ret;
>   }
>   #else
>   static int __remove_section(struct zone *zone, struct mem_section *ms)