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>

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 5b74de6702e06587e0d4f36060f810526ff8fbe3..2311f1585744d4f69fddc1780368f522f26b4142 100644 (file)
--- a/mm/page_alloc.c
+++ b/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, unsigned long start_pfn,
 
        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;
-
-               /* if the two regions intersect */
                if (!(zone_start_pfn >= end_pfn || zone_end_pfn <= start_pfn))
                        z->present_pages += min(end_pfn, zone_end_pfn) -
                                            max(start_pfn, zone_start_pfn);