Re: [PATCH 5/10] memory-hotplug : memory-hotplug: check page typein get_page_bootmem

From: Yasuaki Ishimatsu
Date: Thu Oct 18 2012 - 20:50:27 EST


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@xxxxxxxxxxxxxx> 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@xxxxxxxxxx>
CC: Jiang Liu <liuj97@xxxxxxxxx>
CC: Len Brown <len.brown@xxxxxxxxx>
CC: Christoph Lameter <cl@xxxxxxxxx>
Cc: Minchan Kim <minchan.kim@xxxxxxxxx>
CC: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
CC: KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxxxxxxx>
CC: Wen Congyang <wency@xxxxxxxxxxxxxx>
Signed-off-by: Yasuaki Ishimatsu <isimatu.yasuaki@xxxxxxxxxxxxxx>
---
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

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