[ 70/72] mm/memory-hotplug: fix lowmem count overflow when offline pages

From: Greg Kroah-Hartman
Date: Fri Jul 19 2013 - 01:27:32 EST


3.10-stable review patch. If anyone has any objections, please let me know.

------------------

From: Wanpeng Li <liwanp@xxxxxxxxxxxxxxxxxx>

commit cea27eb2a202959783f81254c48c250ddd80e129 upstream.

The logic for the memory-remove code fails to correctly account the
Total High Memory when a memory block which contains High Memory is
offlined as shown in the example below. The following patch fixes it.

Before logic memory remove:

MemTotal: 7603740 kB
MemFree: 6329612 kB
Buffers: 94352 kB
Cached: 872008 kB
SwapCached: 0 kB
Active: 626932 kB
Inactive: 519216 kB
Active(anon): 180776 kB
Inactive(anon): 222944 kB
Active(file): 446156 kB
Inactive(file): 296272 kB
Unevictable: 0 kB
Mlocked: 0 kB
HighTotal: 7294672 kB
HighFree: 5704696 kB
LowTotal: 309068 kB
LowFree: 624916 kB

After logic memory remove:

MemTotal: 7079452 kB
MemFree: 5805976 kB
Buffers: 94372 kB
Cached: 872000 kB
SwapCached: 0 kB
Active: 626936 kB
Inactive: 519236 kB
Active(anon): 180780 kB
Inactive(anon): 222944 kB
Active(file): 446156 kB
Inactive(file): 296292 kB
Unevictable: 0 kB
Mlocked: 0 kB
HighTotal: 7294672 kB
HighFree: 5181024 kB
LowTotal: 4294752076 kB
LowFree: 624952 kB

[mhocko@xxxxxxx: fix CONFIG_HIGHMEM=n build]
Signed-off-by: Wanpeng Li <liwanp@xxxxxxxxxxxxxxxxxx>
Reviewed-by: Michal Hocko <mhocko@xxxxxxx>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
Cc: David Rientjes <rientjes@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
mm/page_alloc.c | 4 ++++
1 file changed, 4 insertions(+)

--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -6142,6 +6142,10 @@ __offline_isolated_pages(unsigned long s
list_del(&page->lru);
rmv_page_order(page);
zone->free_area[order].nr_free--;
+#ifdef CONFIG_HIGHMEM
+ if (PageHighMem(page))
+ totalhigh_pages -= 1 << order;
+#endif
for (i = 0; i < (1 << order); i++)
SetPageReserved((page+i));
pfn += (1 << order);


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