Messages in this thread | | | Date | Tue, 20 Nov 2012 19:03:30 +0800 | From | Jaegeuk Hanse <> | Subject | Re: [PATCH v3 06/12] memory-hotplug: unregister memory section on SPARSEMEM_VMEMMAP |
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On 11/20/2012 05:37 PM, Wen Congyang wrote: > At 11/20/2012 02:58 PM, Jaegeuk Hanse Wrote: >> On 11/20/2012 02:55 PM, Wen Congyang wrote: >>> 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. >> Hi Congyang, >> >> Thanks for you reponse. But I mean why return (unsigned long)(mem_map - >> (section_nr_to_pfn(pnum))); in function sparse_encode_mem_map, and then >> return ((struct page *)coded_mem_map) + section_nr_to_pfn(pnum); in >> funtion sparse_decode_mem_map instead of just store mem_map in >> ms->section_mep_map directly. > I don't know why. I try to find the reason, but I don't find any > place to use the pfn stored in the mem_map except in the decode > function. Maybe the designer doesn't want us to access the mem_map > directly.
It seems that mem_map is per node, but pfn is real pfn. you can check __page_to_pfn.
> > Thanks > Wen Congyang > >> Regards, >> Jaegeuk >> >>> 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) >>
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