Re: [PATCH RESEND] memory hotplug: fix a double register sectioninfo bug

From: Yasuaki Ishimatsu
Date: Fri Sep 14 2012 - 07:00:50 EST


2012/09/14 12:43, qiuxishi wrote:
There may be a bug when registering section info. For example, on
my Itanium platform, the pfn range of node0 includes the other nodes,
so other nodes' section info will be double registered, and memmap's
page count will equal to 3.

node0: start_pfn=0x100, spanned_pfn=0x20fb00, present_pfn=0x7f8a3, => 0x000100-0x20fc00
node1: start_pfn=0x80000, spanned_pfn=0x80000, present_pfn=0x80000, => 0x080000-0x100000
node2: start_pfn=0x100000, spanned_pfn=0x80000, present_pfn=0x80000, => 0x100000-0x180000
node3: start_pfn=0x180000, spanned_pfn=0x80000, present_pfn=0x80000, => 0x180000-0x200000


When hot remove memory, we can't free the memmap's page because
page_count() is 2 after put_page_bootmem().


Signed-off-by: Xishi Qiu <qiuxishi@xxxxxxxxxx>
Signed-off-by: Jiang Liu <jiang.liu@xxxxxxxxxx>
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))

I cannot judge whether your configuration is correct or not.
Thus if it is correct, I want a comment of why the node check is
needed. In usual configuration, a node does not span the other one.
So it is natural that "pfn_to_nid(pfn) is same as "pgdat->node_id".
Thus we may remove the node check in the future.

Yasuaki Ishimatsu

+ register_page_bootmem_info_section(pfn);
+ }

To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at
Please read the FAQ at