revert "mm: fix-up zone present pages"

Revert commit 7f1290f2f2a4 ("mm: fix-up zone present pages")

That patch tried to fix a issue when calculating zone->present_pages,
but it caused a regression on 32bit systems with HIGHMEM. With that
change, 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
buddy allocator. Because highmem pages are not freed by bootmem
allocator, all highmem zones' present_pages becomes zero.

Various options for improving the situation are being discussed but for
now, let's return to the 3.6 code.

Cc: Jianguo Wu <[e-mail]>
Cc: Jiang Liu <[e-mail]>
Cc: Petr Tesarik <[e-mail]>
Cc: "Luck, Tony" <[e-mail]>
Cc: Mel Gorman <[e-mail]>
Cc: Yinghai Lu <[e-mail]>
Cc: Minchan Kim <[e-mail]>
Cc: Johannes Weiner <[e-mail]>
Acked-by: David Rientjes <[e-mail]>
Tested-by: Chris Clayton <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

arch/ia64/mm/init.c

···
 
 	high_memory = __va(max_low_pfn * PAGE_SIZE);
 
-	reset_zone_present_pages();
 	for_each_online_pgdat(pgdat)
 		if (pgdat->bdata->node_bootmem_map)
 			totalram_pages += free_all_bootmem_node(pgdat);

include/linux/mm.h

···
 static inline bool page_is_guard(struct page *page) { return false; }
 #endif /* CONFIG_DEBUG_PAGEALLOC */
 
-extern void reset_zone_present_pages(void);
-extern void fixup_zone_present_pages(int nid, unsigned long start_pfn,
-				unsigned long end_pfn);
-
 #endif /* __KERNEL__ */
 #endif /* _LINUX_MM_H */

mm/bootmem.c

···
 			int order = ilog2(BITS_PER_LONG);
 
 			__free_pages_bootmem(pfn_to_page(start), order);
-			fixup_zone_present_pages(page_to_nid(pfn_to_page(start)),
-					start, start + BITS_PER_LONG);
 			count += BITS_PER_LONG;
 			start += BITS_PER_LONG;
 		} else {
···
 				if (vec & 1) {
 					page = pfn_to_page(start + off);
 					__free_pages_bootmem(page, 0);
-					fixup_zone_present_pages(
-						page_to_nid(page),
-						start + off, start + off + 1);
 					count++;
 				}
 				vec >>= 1;
···
 	pages = bdata->node_low_pfn - bdata->node_min_pfn;
 	pages = bootmem_bootmap_pages(pages);
 	count += pages;
-	while (pages--) {
-		fixup_zone_present_pages(page_to_nid(page),
-				page_to_pfn(page), page_to_pfn(page) + 1);
+	while (pages--)
 		__free_pages_bootmem(page++, 0);
-	}
 
 	bdebug("nid=%td released=%lx\n", bdata - bootmem_node_data, count);
 

mm/memory_hotplug.c

···
 void __ref put_page_bootmem(struct page *page)
 {
 	unsigned long type;
-	struct zone *zone;
 
 	type = (unsigned long) page->lru.next;
 	BUG_ON(type < MEMORY_HOTPLUG_MIN_BOOTMEM_TYPE ||
···
 		set_page_private(page, 0);
 		INIT_LIST_HEAD(&page->lru);
 		__free_pages_bootmem(page, 0);
-
-		zone = page_zone(page);
-		zone_span_writelock(zone);
-		zone->present_pages++;
-		zone_span_writeunlock(zone);
-		totalram_pages++;
 	}
 
 }

mm/nobootmem.c

···
 		return 0;
 
 	__free_pages_memory(start_pfn, end_pfn);
-	fixup_zone_present_pages(pfn_to_nid(start >> PAGE_SHIFT),
-			start_pfn, end_pfn);
 
 	return end_pfn - start_pfn;
 }
···
 	phys_addr_t start, end, size;
 	u64 i;
 
-	reset_zone_present_pages();
 	for_each_free_mem_range(i, MAX_NUMNODES, &start, &end, NULL)
 		count += __free_memory_core(start, end);
 

mm/page_alloc.c

···
 	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);
-	}
-}