Re: [PATCH v3 06/12] memory-hotplug: unregister memory section on SPARSEMEM_VMEMMAP

Wen Congyang
2012-11-20T06:49:22Z

At 11/20/2012 02:22 PM, Jaegeuk Hanse Wrote:
> 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?

The memmap is aligned, and the low bits are zero. We store some information
in these bits. So we need to encode/decode memmap here.

Thanks
Wen Congyang

>
> 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)
>
>