mm/memory-hotplug: fix lowmem count overflow when offline pages

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

[[email protected]: fix CONFIG_HIGHMEM=n build]
Signed-off-by: Wanpeng Li <[email protected]>
Reviewed-by: Michal Hocko <[email protected]>
Cc: KAMEZAWA Hiroyuki <[email protected]>
Cc: David Rientjes <[email protected]>
Cc: <[email protected]>	[2.6.24+]
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index a662c74a0f5df30f7a3d116fd98e54c2cb77688a..d711dcdda36275d82c09e7d72267ad00586d41ff 100644 (file)
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -6185,6 +6185,10 @@ __offline_isolated_pages(unsigned long start_pfn, unsigned long end_pfn)
                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);