linux-kernel - [002/121] mm/memory-hotplug: fix lowmem count overflow when offline pages

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Message-ID: <lsq.1378608721.274378007@decadent.org.uk>
Date:	Sun, 08 Sep 2013 03:52:01 +0100
From:	Ben Hutchings <ben@...adent.org.uk>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:	akpm@...ux-foundation.org,
	"Wanpeng Li" <liwanp@...ux.vnet.ibm.com>,
	"Zhouping Liu" <zliu@...hat.com>,
	"David Rientjes" <rientjes@...gle.com>,
	"KAMEZAWA Hiroyuki" <kamezawa.hiroyu@...fujitsu.com>,
	"Linus Torvalds" <torvalds@...ux-foundation.org>,
	"Michal Hocko" <mhocko@...e.cz>
Subject: [002/121] mm/memory-hotplug: fix lowmem count overflow when
 offline pages

3.2.51-rc1 review patch.  If anyone has any objections, please let me know.

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

From: Wanpeng Li <liwanp@...ux.vnet.ibm.com>

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@...e.cz: fix CONFIG_HIGHMEM=n build]
Signed-off-by: Wanpeng Li <liwanp@...ux.vnet.ibm.com>
Reviewed-by: Michal Hocko <mhocko@...e.cz>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Cc: David Rientjes <rientjes@...gle.com>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
[Backported for 3.4-stable. Adjusted context.]
Signed-off-by: Zhouping Liu <zliu@...hat.com>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 mm/page_alloc.c | 4 ++++
 1 file changed, 4 insertions(+)

--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -5777,6 +5777,10 @@ __offline_isolated_pages(unsigned long s
 		zone->free_area[order].nr_free--;
 		__mod_zone_page_state(zone, NR_FREE_PAGES,
 				      - (1UL << order));
+#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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