Patchwork [5/10] memory-hotplug : memory-hotplug: check page type in get_page_bootmem

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Submitter Yasuaki Ishimatsu
Date Oct. 5, 2012, 2:32 a.m.
Message ID <506E46B6.3060502@jp.fujitsu.com>
Download mbox | patch
Permalink /patch/189398/
State Not Applicable
Headers show

Comments

Yasuaki Ishimatsu - Oct. 5, 2012, 2:32 a.m.
The function get_page_bootmem() may be called more than one time to the same
page. There is no need to set page's type, private if the function is not
the first time called to the page.

Note: the patch is just optimization and does not fix any problem.

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 |   15 +++++++++++----
 1 file changed, 11 insertions(+), 4 deletions(-)
KOSAKI Motohiro - Oct. 12, 2012, 7:28 p.m.
On Thu, Oct 4, 2012 at 10:32 PM, Yasuaki Ishimatsu
<isimatu.yasuaki@jp.fujitsu.com> wrote:
> The function get_page_bootmem() may be called more than one time to the same
> page. There is no need to set page's type, private if the function is not
> the first time called to the page.
>
> Note: the patch is just optimization and does not fix any problem.
>
> 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 |   15 +++++++++++----
>  1 file changed, 11 insertions(+), 4 deletions(-)
>
> Index: linux-3.6/mm/memory_hotplug.c
> ===================================================================
> --- linux-3.6.orig/mm/memory_hotplug.c  2012-10-04 18:29:58.284676075 +0900
> +++ linux-3.6/mm/memory_hotplug.c       2012-10-04 18:30:03.454680542 +0900
> @@ -95,10 +95,17 @@ static void release_memory_resource(stru
>  static void get_page_bootmem(unsigned long info,  struct page *page,
>                              unsigned long type)
>  {
> -       page->lru.next = (struct list_head *) type;
> -       SetPagePrivate(page);
> -       set_page_private(page, info);
> -       atomic_inc(&page->_count);
> +       unsigned long page_type;
> +
> +       page_type = (unsigned long)page->lru.next;

If I understand correctly, page->lru.next might be uninitialized yet.

Moreover, I have no seen any good effect in this patch. I don't understand
why we need to increase code complexity.



> +       if (page_type < MEMORY_HOTPLUG_MIN_BOOTMEM_TYPE ||
> +           page_type > MEMORY_HOTPLUG_MAX_BOOTMEM_TYPE){
> +               page->lru.next = (struct list_head *)type;
> +               SetPagePrivate(page);
> +               set_page_private(page, info);
> +               atomic_inc(&page->_count);
> +       } else
> +               atomic_inc(&page->_count);
>  }
>
>  /* reference to __meminit __free_pages_bootmem is valid
>
> --
> To unsubscribe, send a message with 'unsubscribe linux-mm' in
> the body to majordomo@kvack.org.  For more info on Linux MM,
> see: http://www.linux-mm.org/ .
> Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
Yasuaki Ishimatsu - Oct. 19, 2012, 12:49 a.m.
Hi Kosaki,

Sorry for late reply.

2012/10/13 4:28, KOSAKI Motohiro wrote:
> On Thu, Oct 4, 2012 at 10:32 PM, Yasuaki Ishimatsu
> <isimatu.yasuaki@jp.fujitsu.com> wrote:
>> The function get_page_bootmem() may be called more than one time to the same
>> page. There is no need to set page's type, private if the function is not
>> the first time called to the page.
>>
>> Note: the patch is just optimization and does not fix any problem.
>>
>> 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 |   15 +++++++++++----
>>   1 file changed, 11 insertions(+), 4 deletions(-)
>>
>> Index: linux-3.6/mm/memory_hotplug.c
>> ===================================================================
>> --- linux-3.6.orig/mm/memory_hotplug.c  2012-10-04 18:29:58.284676075 +0900
>> +++ linux-3.6/mm/memory_hotplug.c       2012-10-04 18:30:03.454680542 +0900
>> @@ -95,10 +95,17 @@ static void release_memory_resource(stru
>>   static void get_page_bootmem(unsigned long info,  struct page *page,
>>                               unsigned long type)
>>   {
>> -       page->lru.next = (struct list_head *) type;
>> -       SetPagePrivate(page);
>> -       set_page_private(page, info);
>> -       atomic_inc(&page->_count);
>> +       unsigned long page_type;
>> +
>> +       page_type = (unsigned long)page->lru.next;
>
> If I understand correctly, page->lru.next might be uninitialized yet.

Ah yes. I was misunderstanding...

Hi Wen,

When you update the physical hot remove patch-set, please drop the patch.

Thanks,
Yasuaki Ishimatsu  
  
> Moreover, I have no seen any good effect in this patch. I don't understand
> why we need to increase code complexity.
>
>
>
>> +       if (page_type < MEMORY_HOTPLUG_MIN_BOOTMEM_TYPE ||
>> +           page_type > MEMORY_HOTPLUG_MAX_BOOTMEM_TYPE){
>> +               page->lru.next = (struct list_head *)type;
>> +               SetPagePrivate(page);
>> +               set_page_private(page, info);
>> +               atomic_inc(&page->_count);
>> +       } else
>> +               atomic_inc(&page->_count);
>>   }
>>
>>   /* reference to __meminit __free_pages_bootmem is valid
>>
>> --
>> To unsubscribe, send a message with 'unsubscribe linux-mm' in
>> the body to majordomo@kvack.org.  For more info on Linux MM,
>> see: http://www.linux-mm.org/ .
>> Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
> --
> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
> Please read the FAQ at  http://www.tux.org/lkml/
>
Wen Congyang - Oct. 19, 2012, 1:55 a.m.
At 10/19/2012 08:49 AM, Yasuaki Ishimatsu Wrote:
> Hi Kosaki,
> 
> Sorry for late reply.
> 
> 2012/10/13 4:28, KOSAKI Motohiro wrote:
>> On Thu, Oct 4, 2012 at 10:32 PM, Yasuaki Ishimatsu
>> <isimatu.yasuaki@jp.fujitsu.com> wrote:
>>> The function get_page_bootmem() may be called more than one time to
>>> the same
>>> page. There is no need to set page's type, private if the function is
>>> not
>>> the first time called to the page.
>>>
>>> Note: the patch is just optimization and does not fix any problem.
>>>
>>> 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 |   15 +++++++++++----
>>>   1 file changed, 11 insertions(+), 4 deletions(-)
>>>
>>> Index: linux-3.6/mm/memory_hotplug.c
>>> ===================================================================
>>> --- linux-3.6.orig/mm/memory_hotplug.c  2012-10-04 18:29:58.284676075
>>> +0900
>>> +++ linux-3.6/mm/memory_hotplug.c       2012-10-04 18:30:03.454680542
>>> +0900
>>> @@ -95,10 +95,17 @@ static void release_memory_resource(stru
>>>   static void get_page_bootmem(unsigned long info,  struct page *page,
>>>                               unsigned long type)
>>>   {
>>> -       page->lru.next = (struct list_head *) type;
>>> -       SetPagePrivate(page);
>>> -       set_page_private(page, info);
>>> -       atomic_inc(&page->_count);
>>> +       unsigned long page_type;
>>> +
>>> +       page_type = (unsigned long)page->lru.next;
>>
>> If I understand correctly, page->lru.next might be uninitialized yet.
> 
> Ah yes. I was misunderstanding...
> 
> Hi Wen,
> 
> When you update the physical hot remove patch-set, please drop the patch.

OK

Thanks
Wen Congyang

> 
> Thanks,
> Yasuaki Ishimatsu   
>> Moreover, I have no seen any good effect in this patch. I don't
>> understand
>> why we need to increase code complexity.
>>
>>
>>
>>> +       if (page_type < MEMORY_HOTPLUG_MIN_BOOTMEM_TYPE ||
>>> +           page_type > MEMORY_HOTPLUG_MAX_BOOTMEM_TYPE){
>>> +               page->lru.next = (struct list_head *)type;
>>> +               SetPagePrivate(page);
>>> +               set_page_private(page, info);
>>> +               atomic_inc(&page->_count);
>>> +       } else
>>> +               atomic_inc(&page->_count);
>>>   }
>>>
>>>   /* reference to __meminit __free_pages_bootmem is valid
>>>
>>> -- 
>>> To unsubscribe, send a message with 'unsubscribe linux-mm' in
>>> the body to majordomo@kvack.org.  For more info on Linux MM,
>>> see: http://www.linux-mm.org/ .
>>> Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
>> -- 
>> To unsubscribe from this list: send the line "unsubscribe
>> linux-kernel" in
>> the body of a message to majordomo@vger.kernel.org
>> More majordomo info at  http://vger.kernel.org/majordomo-info.html
>> Please read the FAQ at  http://www.tux.org/lkml/
>>
> 
> 
> -- 
> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
> Please read the FAQ at  http://www.tux.org/lkml/
>

Patch

Index: linux-3.6/mm/memory_hotplug.c
===================================================================
--- linux-3.6.orig/mm/memory_hotplug.c	2012-10-04 18:29:58.284676075 +0900
+++ linux-3.6/mm/memory_hotplug.c	2012-10-04 18:30:03.454680542 +0900
@@ -95,10 +95,17 @@  static void release_memory_resource(stru
 static void get_page_bootmem(unsigned long info,  struct page *page,
 			     unsigned long type)
 {
-	page->lru.next = (struct list_head *) type;
-	SetPagePrivate(page);
-	set_page_private(page, info);
-	atomic_inc(&page->_count);
+	unsigned long page_type;
+
+	page_type = (unsigned long)page->lru.next;
+	if (page_type < MEMORY_HOTPLUG_MIN_BOOTMEM_TYPE ||
+	    page_type > MEMORY_HOTPLUG_MAX_BOOTMEM_TYPE){
+		page->lru.next = (struct list_head *)type;
+		SetPagePrivate(page);
+		set_page_private(page, info);
+		atomic_inc(&page->_count);
+	} else
+		atomic_inc(&page->_count);
 }
 
 /* reference to __meminit __free_pages_bootmem is valid