[RFC PATCH] mm: fix up zone's present_pages

[Bob Liu <lliubbo@gmail.com>]

zone->present_pages shoule be:
spanned pages - absent pages - bootmem pages(including memmap pages),
but now it's:
spanned pages - absent pages - memmap pages.
And it didn't consider whether the memmap pages is actully allocated from the
zone or not which may cause problem when memory hotplug is improved recently.

For example:
numa node 1 has ZONE_NORMAL and ZONE_MOVABLE, it's memmap and other bootmem
allocated from ZONE_MOVABLE.
So ZONE_NORMAL's present_pages should be spanned pages - absent pages, but now
it also minus memmap pages, which are actually allocated from ZONE_MOVABLE.
This is wrong and when offlining all memory of this zone:
(zone->present_pages -= offline_pages) will less than 0.
Since present_pages is unsigned long type, that is actually a very large
integer which will cause zone->watermark[WMARK_MIN] becomes a large
integer too(see setup_per_zone_wmarks()).
As a result, totalreserve_pages become a large integer also and finally memory
allocating will fail in __vm_enough_memory().

Related discuss:
http://lkml.org/lkml/2012/11/5/866
https://patchwork.kernel.org/patch/1346751/

Related patches in mmotm:
mm: fix-up zone present pages(7f1290f2f2a4d2c) (sometimes cause egression)
mm: fix a regression with HIGHMEM(fe2cebd5a259eec) (Andrew have some feedback)

Jiang Liu have sent a series patches to fix this issue by adding a
managed_pages area to zone struct:
[RFT PATCH v1 0/5] fix up inaccurate zone->present_pages

But i think it's too complicated.
Mine is based on the two related patches already in mmotm(need to revert them
first)
It fix the calculation of zone->present_pages by:
1. Reset the zone->present_pages to zero before
free_all_bootmem(),free_all_bootmem_node() and free_low_memory_core_early().
I think these should already included all path in all arch.

2. If there is a page freed to buddy system in __free_pages_bootmem(),
add zone->present_pages accrodingly.

Note this patch assumes that bootmem won't use memory above ZONE_HIGHMEM, so
only zones below ZONE_HIGHMEM are reset/fixed. If not, some update is needed.
For ZONE_HIGHMEM, only fix it's init value to:
panned_pages - absent_pages in free_area_init_core().

Only did some simple test currently.

Signed-off-by: Jianguo Wu <wujianguo@huawei.com>
Signed-off-by: Jiang Liu <jiang.liu@huawei.com>
Signed-off-by: Bob Liu <lliubbo@gmail.com>
---
 include/linux/mm.h |    3 +++
 mm/bootmem.c       |    2 ++
 mm/nobootmem.c     |    1 +
 mm/page_alloc.c    |   49 +++++++++++++++++++++++++++++++++++++------------
 4 files changed, 43 insertions(+), 12 deletions(-)

diff --git a/include/linux/mm.h b/include/linux/mm.h
index 7b03cab..3b40eb6 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -1763,5 +1763,8 @@ static inline unsigned int debug_guardpage_minorder(void) { return 0; }
 static inline bool page_is_guard(struct page *page) { return false; }
 #endif /* CONFIG_DEBUG_PAGEALLOC */
 
+extern void reset_lowmem_zone_present_pages_pernode(pg_data_t *pgdat);
+extern void reset_lowmem_zone_present_pages(void);
+
 #endif /* __KERNEL__ */
 #endif /* _LINUX_MM_H */
diff --git a/mm/bootmem.c b/mm/bootmem.c
index 26d057a..661775b 100644
--- a/mm/bootmem.c
+++ b/mm/bootmem.c
@@ -238,6 +238,7 @@ static unsigned long __init free_all_bootmem_core(bootmem_data_t *bdata)
 unsigned long __init free_all_bootmem_node(pg_data_t *pgdat)
 {
 	register_page_bootmem_info_node(pgdat);
+	reset_lowmem_zone_present_pages_pernode(pgdat);
 	return free_all_bootmem_core(pgdat->bdata);
 }
 
@@ -251,6 +252,7 @@ unsigned long __init free_all_bootmem(void)
 	unsigned long total_pages = 0;
 	bootmem_data_t *bdata;
 
+	reset_lowmem_zone_present_pages();
 	list_for_each_entry(bdata, &bdata_list, list)
 		total_pages += free_all_bootmem_core(bdata);
 
diff --git a/mm/nobootmem.c b/mm/nobootmem.c
index bd82f6b..378d50a 100644
--- a/mm/nobootmem.c
+++ b/mm/nobootmem.c
@@ -126,6 +126,7 @@ unsigned long __init free_low_memory_core_early(int nodeid)
 	phys_addr_t start, end, size;
 	u64 i;
 
+	reset_lowmem_zone_present_pages();
 	for_each_free_mem_range(i, MAX_NUMNODES, &start, &end, NULL)
 		count += __free_memory_core(start, end);
 
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 07425a7..76d37f0 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -735,6 +735,7 @@ void __meminit __free_pages_bootmem(struct page *page, unsigned int order)
 {
 	unsigned int nr_pages = 1 << order;
 	unsigned int loop;
+	struct zone *zone;
 
 	prefetchw(page);
 	for (loop = 0; loop < nr_pages; loop++) {
@@ -748,6 +749,9 @@ void __meminit __free_pages_bootmem(struct page *page, unsigned int order)
 
 	set_page_refcounted(page);
 	__free_pages(page, order);
+	zone = page_zone(page);
+	WARN_ON(!(is_normal(zone) || is_dma(zone) || is_dma32(zone)));
+	zone->present_pages += nr_pages;
 }
 
 #ifdef CONFIG_CMA
@@ -4547,18 +4551,20 @@ static void __paginginit free_area_init_core(struct pglist_data *pgdat,
 		 * is used by this zone for memmap. This affects the watermark
 		 * and per-cpu initialisations
 		 */
-		memmap_pages =
-			PAGE_ALIGN(size * sizeof(struct page)) >> PAGE_SHIFT;
-		if (realsize >= memmap_pages) {
-			realsize -= memmap_pages;
-			if (memmap_pages)
-				printk(KERN_DEBUG
-				       "  %s zone: %lu pages used for memmap\n",
-				       zone_names[j], memmap_pages);
-		} else
-			printk(KERN_WARNING
-				"  %s zone: %lu pages exceeds realsize %lu\n",
-				zone_names[j], memmap_pages, realsize);
+		if (j < ZONE_HIGHMEM) {
+			memmap_pages =
+				PAGE_ALIGN(size * sizeof(struct page)) >> PAGE_SHIFT;
+			if (realsize >= memmap_pages) {
+				realsize -= memmap_pages;
+				if (memmap_pages)
+					printk(KERN_DEBUG
+							"  %s zone: %lu pages used for memmap\n",
+							zone_names[j], memmap_pages);
+			} else
+				printk(KERN_WARNING
+						"  %s zone: %lu pages exceeds realsize %lu\n",
+						zone_names[j], memmap_pages, realsize);
+		}
 
 		/* Account for reserved pages */
 		if (j == 0 && realsize > dma_reserve) {
@@ -6143,3 +6149,22 @@ void dump_page(struct page *page)
 	dump_page_flags(page->flags);
 	mem_cgroup_print_bad_page(page);
 }
+
+/* reset zone->present_pages to 0 for zones below ZONE_HIGHMEM */
+void reset_lowmem_zone_present_pages_pernode(pg_data_t *pgdat)
+{
+	int i;
+	struct zone *z;
+	for (i = 0; i < ZONE_HIGHMEM; i++) {
+		z = pgdat->node_zones + i;
+		z->present_pages = 0;
+	}
+}
+
+void reset_lowmem_zone_present_pages(void)
+{
+	int nid;
+
+	for_each_node_state(nid, N_HIGH_MEMORY)
+		reset_lowmem_zone_present_pages_pernode(NODE_DATA(nid));
+}
-- 
1.7.9.5


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