linux-kernel - [PATCH] memory hotplug: avoid double registration on ia64 platform

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Date:	Fri, 17 Aug 2012 15:52:47 +0800
From:	qiuxishi <qiuxishi@...il.com>
To:	akpm@...ux-foundation.org, mgorman@...e.de, tony.luck@...el.com,
	yinghai@...nel.org, jiang.liu@...wei.com
CC:	qiuxishi@...wei.com, bessel.wang@...wei.com, wujianguo@...wei.com,
	paul.gortmaker@...driver.com, kamezawa.hiroyu@...fujitsu.com,
	kosaki.motohiro@...fujitsu.com, rientjes@...gle.com,
	minchan@...nel.org, chenkeping@...wei.com, linux-mm@...ck.org,
	stable@...r.kernel.org, linux-kernel@...r.kernel.org,
	liuj97@...il.com
Subject: [PATCH] memory hotplug: avoid double registration on ia64 platform

From: Xishi Qiu <qiuxishi@...wei.com>

Hi all,
There may be have a bug when register section info. For example, on
an Itanium platform, the pfn range of node0 includes the other nodes.
So when hot remove memory, we can't free the memmap's page because
page_count() is 2 after put_page_bootmem().

sparse_remove_one_section()->free_section_usemap()->free_map_bootmem()
->put_page_bootmem()

pgdat0: start_pfn=0x100,    spanned_pfn=0x20fb00, present_pfn=0x7f8a3, => 0x100-0x20fc00
pgdat1: start_pfn=0x80000,  spanned_pfn=0x80000,  present_pfn=0x80000, => 0x80000-0x100000
pgdat2: start_pfn=0x100000, spanned_pfn=0x80000,  present_pfn=0x80000, => 0x100000-0x180000
pgdat3: start_pfn=0x180000, spanned_pfn=0x80000,  present_pfn=0x80000, => 0x180000-0x200000


Signed-off-by: Xishi Qiu <qiuxishi@...wei.com>
---
 mm/memory_hotplug.c |   10 ++++------
 1 files changed, 4 insertions(+), 6 deletions(-)

diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index 2adbcac..cf493c7 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -126,9 +126,6 @@ static void register_page_bootmem_info_section(unsigned long start_pfn)
 	struct mem_section *ms;
 	struct page *page, *memmap;

-	if (!pfn_valid(start_pfn))
-		return;
-
 	section_nr = pfn_to_section_nr(start_pfn);
 	ms = __nr_to_section(section_nr);

@@ -187,9 +184,10 @@ void register_page_bootmem_info_node(struct pglist_data *pgdat)
 	end_pfn = pfn + pgdat->node_spanned_pages;

 	/* register_section info */
-	for (; pfn < end_pfn; pfn += PAGES_PER_SECTION)
-		register_page_bootmem_info_section(pfn);
-
+	for (; pfn < end_pfn; pfn += PAGES_PER_SECTION) {
+		if (pfn_valid(pfn) && (pfn_to_nid(pfn) == node))
+			register_page_bootmem_info_section(pfn);
+	}
 }
 #endif /* !CONFIG_SPARSEMEM_VMEMMAP */

-- 1.7.1
--
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