mm: fix-up zone present pages

I think zone->present_pages indicates pages that buddy system can management,
it should be:

	zone->present_pages = spanned pages - absent pages - bootmem pages,

but is now:
	zone->present_pages = spanned pages - absent pages - memmap pages.

spanned pages: total size, including holes.
absent pages: holes.
bootmem pages: pages used in system boot, managed by bootmem allocator.
memmap pages: pages used by page structs.

This may cause zone->present_pages less than it should be.  For example,
numa node 1 has ZONE_NORMAL and ZONE_MOVABLE, it's memmap and other
bootmem will be allocated from ZONE_MOVABLE, so ZONE_NORMAL's
present_pages should be spanned pages - absent pages, but now it also
minus memmap pages(free_area_init_core), which are actually allocated from
ZONE_MOVABLE.  When offlining all memory of a zone, this will cause
zone->present_pages less than 0, because present_pages is unsigned long
type, it is actually a very large integer, it indirectly caused
zone->watermark[WMARK_MIN] becomes a large
integer(setup_per_zone_wmarks()), than cause totalreserve_pages become a
large integer(calculate_totalreserve_pages()), and finally cause memory
allocating failure when fork process(__vm_enough_memory()).

[root@localhost ~]# dmesg
-bash: fork: Cannot allocate memory

I think the bug described in

  http://marc.info/?l=linux-mm&m=134502182714186&w=2

is also caused by wrong zone present pages.

This patch intends to fix-up zone->present_pages when memory are freed to
buddy system on x86_64 and IA64 platforms.

Signed-off-by: Jianguo Wu <wujianguo@huawei.com>
Signed-off-by: Jiang Liu <jiang.liu@huawei.com>
Reported-by: Petr Tesarik <ptesarik@suse.cz>
Tested-by: Petr Tesarik <ptesarik@suse.cz>
Cc: "Luck, Tony" <tony.luck@intel.com>
Cc: Mel Gorman <mel@csn.ul.ie>
Cc: Yinghai Lu <yinghai@kernel.org>
Cc: Minchan Kim <minchan.kim@gmail.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 34 insertions, 0 deletions

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 8ac5938..00750bc 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -6087,3 +6087,37 @@ void dump_page(struct page *page)
 	dump_page_flags(page->flags);
 	mem_cgroup_print_bad_page(page);
 }
+
+/* reset zone->present_pages */
+void reset_zone_present_pages(void)
+{
+	struct zone *z;
+	int i, nid;
+
+	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;
+		}
+	}
+}
+
+/* calculate zone's present pages in buddy system */
+void fixup_zone_present_pages(int nid, unsigned long start_pfn,
+				unsigned long end_pfn)
+{
+	struct zone *z;
+	unsigned long zone_start_pfn, zone_end_pfn;
+	int i;
+
+	for (i = 0; i < MAX_NR_ZONES; i++) {
+		z = NODE_DATA(nid)->node_zones + i;
+		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);
+	}
+}