[RFC,v9,05/21] memory-hotplug: check whether memory is present or not

From: Yasuaki Ishimatsu <isimatu.yasuaki@jp.fujitsu.com>

If system supports memory hot-remove, online_pages() may online removed pages.
So online_pages() need to check whether onlining pages are present or not.

CC: David Rientjes <rientjes@google.com>
CC: Jiang Liu <liuj97@gmail.com>
CC: Len Brown <len.brown@intel.com>
CC: Benjamin Herrenschmidt <benh@kernel.crashing.org>
CC: Paul Mackerras <paulus@samba.org>
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>
---
 include/linux/mmzone.h |   19 +++++++++++++++++++
 mm/memory_hotplug.c    |   13 +++++++++++++
 2 files changed, 32 insertions(+), 0 deletions(-)

Hi, ishimatsu

At 09/05/2012 05:25 PM, wency@cn.fujitsu.com Wrote:
> From: Yasuaki Ishimatsu <isimatu.yasuaki@jp.fujitsu.com>
> 
> If system supports memory hot-remove, online_pages() may online removed pages.
> So online_pages() need to check whether onlining pages are present or not.

Because we use memory_block_change_state() to hotremoving memory, I think
this patch can be removed. What do you think?

Thanks
Wen Congyang

> 
> CC: David Rientjes <rientjes@google.com>
> CC: Jiang Liu <liuj97@gmail.com>
> CC: Len Brown <len.brown@intel.com>
> CC: Benjamin Herrenschmidt <benh@kernel.crashing.org>
> CC: Paul Mackerras <paulus@samba.org>
> 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>
> ---
>  include/linux/mmzone.h |   19 +++++++++++++++++++
>  mm/memory_hotplug.c    |   13 +++++++++++++
>  2 files changed, 32 insertions(+), 0 deletions(-)
> 
> diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
> index 2daa54f..ac3ae30 100644
> --- a/include/linux/mmzone.h
> +++ b/include/linux/mmzone.h
> @@ -1180,6 +1180,25 @@ void sparse_init(void);
>  #define sparse_index_init(_sec, _nid)  do {} while (0)
>  #endif /* CONFIG_SPARSEMEM */
>  
> +#ifdef CONFIG_SPARSEMEM
> +static inline int pfns_present(unsigned long pfn, unsigned long nr_pages)
> +{
> +	int i;
> +	for (i = 0; i < nr_pages; i++) {
> +		if (pfn_present(pfn + i))
> +			continue;
> +		else
> +			return -EINVAL;
> +	}
> +	return 0;
> +}
> +#else
> +static inline int pfns_present(unsigned long pfn, unsigned long nr_pages)
> +{
> +	return 0;
> +}
> +#endif /* CONFIG_SPARSEMEM*/
> +
>  #ifdef CONFIG_NODES_SPAN_OTHER_NODES
>  bool early_pfn_in_nid(unsigned long pfn, int nid);
>  #else
> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
> index 49f7747..299747d 100644
> --- a/mm/memory_hotplug.c
> +++ b/mm/memory_hotplug.c
> @@ -467,6 +467,19 @@ int __ref online_pages(unsigned long pfn, unsigned long nr_pages)
>  	struct memory_notify arg;
>  
>  	lock_memory_hotplug();
> +	/*
> +	 * If system supports memory hot-remove, the memory may have been
> +	 * removed. So we check whether the memory has been removed or not.
> +	 *
> +	 * Note: When CONFIG_SPARSEMEM is defined, pfns_present() become
> +	 *       effective. If CONFIG_SPARSEMEM is not defined, pfns_present()
> +	 *       always returns 0.
> +	 */
> +	ret = pfns_present(pfn, nr_pages);
> +	if (ret) {
> +		unlock_memory_hotplug();
> +		return ret;
> +	}
>  	arg.start_pfn = pfn;
>  	arg.nr_pages = nr_pages;
>  	arg.status_change_nid = -1;

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Hi Wen,

2012/09/11 11:15, Wen Congyang wrote:
> Hi, ishimatsu
>
> At 09/05/2012 05:25 PM, wency@cn.fujitsu.com Wrote:
>> From: Yasuaki Ishimatsu <isimatu.yasuaki@jp.fujitsu.com>
>>
>> If system supports memory hot-remove, online_pages() may online removed pages.
>> So online_pages() need to check whether onlining pages are present or not.
>
> Because we use memory_block_change_state() to hotremoving memory, I think
> this patch can be removed. What do you think?

Pleae teach me detals a little more. If we use memory_block_change_state(),
does the conflict never occur? Why?

Thansk,
Yasuaki Ishimatsu

> Thanks
> Wen Congyang
>
>>
>> CC: David Rientjes <rientjes@google.com>
>> CC: Jiang Liu <liuj97@gmail.com>
>> CC: Len Brown <len.brown@intel.com>
>> CC: Benjamin Herrenschmidt <benh@kernel.crashing.org>
>> CC: Paul Mackerras <paulus@samba.org>
>> 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>
>> ---
>>   include/linux/mmzone.h |   19 +++++++++++++++++++
>>   mm/memory_hotplug.c    |   13 +++++++++++++
>>   2 files changed, 32 insertions(+), 0 deletions(-)
>>
>> diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
>> index 2daa54f..ac3ae30 100644
>> --- a/include/linux/mmzone.h
>> +++ b/include/linux/mmzone.h
>> @@ -1180,6 +1180,25 @@ void sparse_init(void);
>>   #define sparse_index_init(_sec, _nid)  do {} while (0)
>>   #endif /* CONFIG_SPARSEMEM */
>>
>> +#ifdef CONFIG_SPARSEMEM
>> +static inline int pfns_present(unsigned long pfn, unsigned long nr_pages)
>> +{
>> +	int i;
>> +	for (i = 0; i < nr_pages; i++) {
>> +		if (pfn_present(pfn + i))
>> +			continue;
>> +		else
>> +			return -EINVAL;
>> +	}
>> +	return 0;
>> +}
>> +#else
>> +static inline int pfns_present(unsigned long pfn, unsigned long nr_pages)
>> +{
>> +	return 0;
>> +}
>> +#endif /* CONFIG_SPARSEMEM*/
>> +
>>   #ifdef CONFIG_NODES_SPAN_OTHER_NODES
>>   bool early_pfn_in_nid(unsigned long pfn, int nid);
>>   #else
>> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
>> index 49f7747..299747d 100644
>> --- a/mm/memory_hotplug.c
>> +++ b/mm/memory_hotplug.c
>> @@ -467,6 +467,19 @@ int __ref online_pages(unsigned long pfn, unsigned long nr_pages)
>>   	struct memory_notify arg;
>>
>>   	lock_memory_hotplug();
>> +	/*
>> +	 * If system supports memory hot-remove, the memory may have been
>> +	 * removed. So we check whether the memory has been removed or not.
>> +	 *
>> +	 * Note: When CONFIG_SPARSEMEM is defined, pfns_present() become
>> +	 *       effective. If CONFIG_SPARSEMEM is not defined, pfns_present()
>> +	 *       always returns 0.
>> +	 */
>> +	ret = pfns_present(pfn, nr_pages);
>> +	if (ret) {
>> +		unlock_memory_hotplug();
>> +		return ret;
>> +	}
>>   	arg.start_pfn = pfn;
>>   	arg.nr_pages = nr_pages;
>>   	arg.status_change_nid = -1;
>


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At 09/11/2012 10:24 AM, Yasuaki Ishimatsu Wrote:
> Hi Wen,
> 
> 2012/09/11 11:15, Wen Congyang wrote:
>> Hi, ishimatsu
>>
>> At 09/05/2012 05:25 PM, wency@cn.fujitsu.com Wrote:
>>> From: Yasuaki Ishimatsu <isimatu.yasuaki@jp.fujitsu.com>
>>>
>>> If system supports memory hot-remove, online_pages() may online
>>> removed pages.
>>> So online_pages() need to check whether onlining pages are present or
>>> not.
>>
>> Because we use memory_block_change_state() to hotremoving memory, I think
>> this patch can be removed. What do you think?
> 
> Pleae teach me detals a little more. If we use memory_block_change_state(),
> does the conflict never occur? Why?

I misunderstand sth, please ignore it.

Wen Congyang

> 
> Thansk,
> Yasuaki Ishimatsu
> 
>> Thanks
>> Wen Congyang
>>
>>>
>>> CC: David Rientjes <rientjes@google.com>
>>> CC: Jiang Liu <liuj97@gmail.com>
>>> CC: Len Brown <len.brown@intel.com>
>>> CC: Benjamin Herrenschmidt <benh@kernel.crashing.org>
>>> CC: Paul Mackerras <paulus@samba.org>
>>> 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>
>>> ---
>>>   include/linux/mmzone.h |   19 +++++++++++++++++++
>>>   mm/memory_hotplug.c    |   13 +++++++++++++
>>>   2 files changed, 32 insertions(+), 0 deletions(-)
>>>
>>> diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
>>> index 2daa54f..ac3ae30 100644
>>> --- a/include/linux/mmzone.h
>>> +++ b/include/linux/mmzone.h
>>> @@ -1180,6 +1180,25 @@ void sparse_init(void);
>>>   #define sparse_index_init(_sec, _nid)  do {} while (0)
>>>   #endif /* CONFIG_SPARSEMEM */
>>>
>>> +#ifdef CONFIG_SPARSEMEM
>>> +static inline int pfns_present(unsigned long pfn, unsigned long
>>> nr_pages)
>>> +{
>>> +    int i;
>>> +    for (i = 0; i < nr_pages; i++) {
>>> +        if (pfn_present(pfn + i))
>>> +            continue;
>>> +        else
>>> +            return -EINVAL;
>>> +    }
>>> +    return 0;
>>> +}
>>> +#else
>>> +static inline int pfns_present(unsigned long pfn, unsigned long
>>> nr_pages)
>>> +{
>>> +    return 0;
>>> +}
>>> +#endif /* CONFIG_SPARSEMEM*/
>>> +
>>>   #ifdef CONFIG_NODES_SPAN_OTHER_NODES
>>>   bool early_pfn_in_nid(unsigned long pfn, int nid);
>>>   #else
>>> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
>>> index 49f7747..299747d 100644
>>> --- a/mm/memory_hotplug.c
>>> +++ b/mm/memory_hotplug.c
>>> @@ -467,6 +467,19 @@ int __ref online_pages(unsigned long pfn,
>>> unsigned long nr_pages)
>>>       struct memory_notify arg;
>>>
>>>       lock_memory_hotplug();
>>> +    /*
>>> +     * If system supports memory hot-remove, the memory may have been
>>> +     * removed. So we check whether the memory has been removed or not.
>>> +     *
>>> +     * Note: When CONFIG_SPARSEMEM is defined, pfns_present() become
>>> +     *       effective. If CONFIG_SPARSEMEM is not defined,
>>> pfns_present()
>>> +     *       always returns 0.
>>> +     */
>>> +    ret = pfns_present(pfn, nr_pages);
>>> +    if (ret) {
>>> +        unlock_memory_hotplug();
>>> +        return ret;
>>> +    }
>>>       arg.start_pfn = pfn;
>>>       arg.nr_pages = nr_pages;
>>>       arg.status_change_nid = -1;
>>
> 
> 
> 

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On 09/11/2012 10:24 AM, Yasuaki Ishimatsu wrote:
> Hi Wen,
>
> 2012/09/11 11:15, Wen Congyang wrote:
>> Hi, ishimatsu
>>
>> At 09/05/2012 05:25 PM, wency@cn.fujitsu.com Wrote:
>>> From: Yasuaki Ishimatsu <isimatu.yasuaki@jp.fujitsu.com>
>>>
>>> If system supports memory hot-remove, online_pages() may online 
>>> removed pages.
>>> So online_pages() need to check whether onlining pages are present 
>>> or not.
>>
>> Because we use memory_block_change_state() to hotremoving memory, I 
>> think
>> this patch can be removed. What do you think?
>
> Pleae teach me detals a little more. If we use 
> memory_block_change_state(),
> does the conflict never occur? Why?

since memory hot-add or hot-remove is based on memblock, if check in 
memory_block_change_state()
can guarantee conflict never occur?

>
> Thansk,
> Yasuaki Ishimatsu
>
>> Thanks
>> Wen Congyang
>>
>>>
>>> CC: David Rientjes <rientjes@google.com>
>>> CC: Jiang Liu <liuj97@gmail.com>
>>> CC: Len Brown <len.brown@intel.com>
>>> CC: Benjamin Herrenschmidt <benh@kernel.crashing.org>
>>> CC: Paul Mackerras <paulus@samba.org>
>>> 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>
>>> ---
>>>   include/linux/mmzone.h |   19 +++++++++++++++++++
>>>   mm/memory_hotplug.c    |   13 +++++++++++++
>>>   2 files changed, 32 insertions(+), 0 deletions(-)
>>>
>>> diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
>>> index 2daa54f..ac3ae30 100644
>>> --- a/include/linux/mmzone.h
>>> +++ b/include/linux/mmzone.h
>>> @@ -1180,6 +1180,25 @@ void sparse_init(void);
>>>   #define sparse_index_init(_sec, _nid)  do {} while (0)
>>>   #endif /* CONFIG_SPARSEMEM */
>>>
>>> +#ifdef CONFIG_SPARSEMEM
>>> +static inline int pfns_present(unsigned long pfn, unsigned long 
>>> nr_pages)
>>> +{
>>> +    int i;
>>> +    for (i = 0; i < nr_pages; i++) {
>>> +        if (pfn_present(pfn + i))
>>> +            continue;
>>> +        else
>>> +            return -EINVAL;
>>> +    }
>>> +    return 0;
>>> +}
>>> +#else
>>> +static inline int pfns_present(unsigned long pfn, unsigned long 
>>> nr_pages)
>>> +{
>>> +    return 0;
>>> +}
>>> +#endif /* CONFIG_SPARSEMEM*/
>>> +
>>>   #ifdef CONFIG_NODES_SPAN_OTHER_NODES
>>>   bool early_pfn_in_nid(unsigned long pfn, int nid);
>>>   #else
>>> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
>>> index 49f7747..299747d 100644
>>> --- a/mm/memory_hotplug.c
>>> +++ b/mm/memory_hotplug.c
>>> @@ -467,6 +467,19 @@ int __ref online_pages(unsigned long pfn, 
>>> unsigned long nr_pages)
>>>       struct memory_notify arg;
>>>
>>>       lock_memory_hotplug();
>>> +    /*
>>> +     * If system supports memory hot-remove, the memory may have been
>>> +     * removed. So we check whether the memory has been removed or 
>>> not.
>>> +     *
>>> +     * Note: When CONFIG_SPARSEMEM is defined, pfns_present() become
>>> +     *       effective. If CONFIG_SPARSEMEM is not defined, 
>>> pfns_present()
>>> +     *       always returns 0.
>>> +     */
>>> +    ret = pfns_present(pfn, nr_pages);
>>> +    if (ret) {
>>> +        unlock_memory_hotplug();
>>> +        return ret;
>>> +    }
>>>       arg.start_pfn = pfn;
>>>       arg.nr_pages = nr_pages;
>>>       arg.status_change_nid = -1;
>>
>
>
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