+ mm-fix-a-regression-with-highmem-introduced-by-changeset-7f1290f2f2a4d.patch added to -mm tree

+ mm-fix-a-regression-with-highmem-introduced-by-changeset-7f1290f2f2a4d.patch added to -mm tree

[akpm]

The patch titled
     Subject: mm: fix a regression with HIGHMEM
has been added to the -mm tree.  Its filename is
     mm-fix-a-regression-with-highmem-introduced-by-changeset-7f1290f2f2a4d.patch

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------------------------------------------------------
From: Jiang Liu <jiang.liu@huawei.com>
Subject: mm: fix a regression with HIGHMEM

Changeset 7f1290f2f2 ("mm: fix-up zone present pages") tried to fix a
issue when calculating zone->present_pages, but it causes a regression to
32bit systems with HIGHMEM.  With that changeset,
reset_zone_present_pages() resets all zone->present_pages to zero, and
fixup_zone_present_pages() is called to recalculate zone->present_pages
when the boot allocator frees core memory pages into the buddy allocator. 
Because highmem pages are not freed by bootmem allocator, all highmem
zones' present_pages becomes zero.

Actually there's no need to recalculate present_pages for the highmem zone
because the bootmem allocator never allocates pages from it.  So fix the
regression by skipping highmem in function reset_zone_present_pages() and
fixup_zone_present_pages().

Signed-off-by: Jiang Liu <jiang.liu@huawei.com>
Signed-off-by: Jianguo Wu <wujianguo@huawei.com>
Reported-by: Maciej Rutecki <maciej.rutecki@gmail.com>
Tested-by: Maciej Rutecki <maciej.rutecki@gmail.com>
Tested-by: Chris Clayton <chris2553@googlemail.com>
Cc: Rafael J. Wysocki <rjw@sisk.pl>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Minchan Kim <minchan@kernel.org>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Michal Hocko <mhocko@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/page_alloc.c |    8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff -puN mm/page_alloc.c~mm-fix-a-regression-with-highmem-introduced-by-changeset-7f1290f2f2a4d mm/page_alloc.c
--- a/mm/page_alloc.c~mm-fix-a-regression-with-highmem-introduced-by-changeset-7f1290f2f2a4d
+++ a/mm/page_alloc.c
@@ -6108,7 +6108,8 @@ void reset_zone_present_pages(void)
 	for_each_node_state(nid, N_HIGH_MEMORY) {
 		for (i = 0; i < MAX_NR_ZONES; i++) {
 			z = NODE_DATA(nid)->node_zones + i;
-			z->present_pages = 0;
+			if (!is_highmem(z))
+				z->present_pages = 0;
 		}
 	}
 }
@@ -6123,10 +6124,11 @@ void fixup_zone_present_pages(int nid, u
 
 	for (i = 0; i < MAX_NR_ZONES; i++) {
 		z = NODE_DATA(nid)->node_zones + i;
+		if (is_highmem(z))
+			continue;
+
 		zone_start_pfn = z->zone_start_pfn;
 		zone_end_pfn = zone_start_pfn + z->spanned_pages;