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

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

[qiuxishi]

From: Xishi Qiu <qiuxishi@huawei.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@huawei.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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Re: [PATCH] memory hotplug: avoid double registration on ia64 platform

[Greg KH]

On Fri, Aug 17, 2012 at 03:52:47PM +0800, qiuxishi wrote:
> From: Xishi Qiu <qiuxishi@huawei.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@huawei.com>
> ---
>  mm/memory_hotplug.c |   10 ++++------
>  1 files changed, 4 insertions(+), 6 deletions(-)

<formletter>

This is not the correct way to submit patches for inclusion in the
stable kernel tree.  Please read Documentation/stable_kernel_rules.txt
for how to do this properly.

</formletter>

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