no bitmap buddy allocator : initialize mem_map considering buddy system (1/4)

diff -puN mm/page_alloc.c~eliminate-bitmap-init mm/page_alloc.c
@@ -62,19 +62,27 @@ unsigned long __initdata nr_kernel_pages
 unsigned long __initdata nr_all_pages;
 
 /*
- * Temporary debugging check for pages not lying within a given zone.
+ * check for pages not lying within a given zone.
  */
-static int bad_range(struct zone *zone, struct page *page)
+static int bad_range_pfn(struct zone *zone, unsigned long pfn)
 {
-	if (page_to_pfn(page) >= zone->zone_start_pfn + zone->spanned_pages)
+	if((pfn < zone->memmap_start_pfn) || (pfn > zone->memmap_end_pfn))
 		return 1;
-	if (page_to_pfn(page) < zone->zone_start_pfn)
+	return 0;
+}
+
+static int bad_range(struct zone *zone, struct page *page)
+{
+	if (bad_range_pfn(zone, page_to_pfn(page)))
 		return 1;
 	if (zone != page_zone(page))
 		return 1;
 	return 0;
 }
 
+/*
+ *  debug check to print bad page.
+ */
 static void bad_page(const char *function, struct page *page)
 {
 	printk(KERN_EMERG "Bad page state at %s (in process '%s', page %p)\n",

@@ -917,6 +925,33 @@ fastcall void free_pages(unsigned long a
 EXPORT_SYMBOL(free_pages);
 
 /*
+ * This function doesn't pass PG_locked pages to buddy allocator.
+ * PG_locked pages are silently removed from buddy system, which are
+ * marked with PG_private and set page_order() to INVALID_PAGE_ORDER.
+ */
+long __init free_pages_at_init(struct page *base, int order)
+{
+	struct page *page;
+	int nr_pages = (1 << order);
+	long nr_freed_pages = 0;
+
+	if (PageReserved(base) || !put_page_testzero(base))
+		return 0;
+
+	for( page = base,nr_freed_pages = 0; page != base + nr_pages; page++) {
+		if (PageLocked(page)) {
+			/* this page is a victim for the buddy allocator. */
+			SetPagePrivate(page);
+			set_page_order(page, PAGE_INVALID_ORDER);
+		} else {
+			free_hot_page(page);
+			nr_freed_pages++;
+		}
+	}
+	return nr_freed_pages;
+}
+
+/*
  * Total amount of free (allocatable) RAM:
  */
 unsigned int nr_free_pages(void)

@@ -1499,6 +1534,109 @@ static void __init calculate_zone_totalp
 	printk(KERN_DEBUG "On node %d totalpages: %lu\n", pgdat->node_id, realtotalpages);
 }
 
+/*
+ * For the buddy system, A page which meets all below conditions must access
+ * an invalid page in __free_pages_bulk() and cause a fault.
+ * (a) its buddy has an invalid pfn , out of mem_map.
+ * (b) access to its invalid buddy cannot be catched by bad_range_pfn().
+ * We cannot use it in the buddy system.
+ *
+ * This calculate_buddy_range() removes some pages.
+ * (1) At first, we check whether a mem_map is sparse or not. If not,
+ *     bad_range_pfn() can catch all invalid access.
+ * (2) We check whether the mem_map is aligned to MAX_ORDER or not.
+ * (3) If the mem_map is not aligned in its start address, we find pages
+ *     which are top of buddy-list in each order and check whether
+ *     their buddy are out of mem_map.If buddy is out of zone, bad_range_pfn()
+ *     can catch it.If in zone, we mark them with PG_locked.
+ * (4) If the mem_map is not aligned in its end addres and the first
+ *     out-of-memmap page is not out-of-zone, we mark the end page
+ *     of it with PG_locked.
+ *
+ * Marked pages are not added to buddy system and we call them victim pages.
+ * Please see free_pages_at_init().
+ */
+
+static void __init calculate_buddy_range(struct zone *zone,
+					 unsigned long start_pfn,
+					 int nr_pages)
+{
+	struct page *base;
+	unsigned long alignment_mask;
+	long start_idx, end_idx, edge_idx, buddy_idx;
+	int order;
+
+	if((zone->zone_start_pfn == start_pfn) &&
+	   (zone->spanned_pages == nr_pages))
+		/*
+		 * memmap is fully contiguous. bad_range_pfn() can catch
+		 * all invalid access. there is nothing to do
+		 */
+		return;
+	start_idx = start_pfn - zone->zone_start_pfn;
+	end_idx = start_idx + nr_pages - 1;
+	alignment_mask = (1 << MAX_ORDER) - 1;
+	base = zone->zone_mem_map;
+	printk("calculate_buddy_range() %lx %d\n",start_pfn, nr_pages);
+
+	if ((start_pfn != zone->memmap_start_pfn) &&
+	    (start_idx & alignment_mask)) {
+		/*
+		 * this mem_map is not aligned and invalid access in this
+		 * mem_map cannot be caught by bad_range_pfn()
+		 */
+		for (edge_idx = start_idx,order = 0;
+		     order < MAX_ORDER;
+		     order++) {
+			if (edge_idx > end_idx)
+				break;
+			buddy_idx = edge_idx ^ (1 << order);
+			if (buddy_idx > end_idx)
+				break;
+			if (buddy_idx < edge_idx) {
+				/*
+				 * Reserve the top page in this order
+				 * as the stopper for buddy allocator.
+				 * Because this page is an only page
+				 * which has an out of range buddy in
+				 * this order.
+				 */
+				printk("victim top page %lx\n",
+				       zone->zone_start_pfn + edge_idx);
+				SetPageLocked(base + edge_idx);
+				edge_idx += (1 << order);
+			}
+		}
+	}
+	/*
+	 *  If end address is not aligned, we remove the last page.
+	 *  This will keep __free_page_bulk() from invalid mem_map access
+	 *  which exceeds the end of mem_map.
+	 *  This victim page can be revived by save_end_victim_zone().
+	 */
+	if ((end_idx & alignment_mask) != alignment_mask) {
+		printk("victim end page %lx\n",
+		       zone->zone_start_pfn + end_idx);
+		SetPageLocked(base + end_idx);
+	}
+	return;
+}
+
+static inline void save_end_victim_zone(struct zone *zone)
+{
+	struct page *page;
+	/*
+	 * zone->memmap_end_pfn is updated now.
+ 	 * bad_range_pfn() can catch invalid access exceeding end of zone.
+	 * if the zone's end page is a victim, we can use it.
+	 */
+	page = zone->zone_mem_map + zone->memmap_end_pfn- zone->zone_start_pfn;
+	if (PageLocked(page)) {
+		ClearPageLocked(page);
+		printk("saved end victim page %lx\n",zone->memmap_end_pfn);
+	}
+	return;
+}
 
 /*
  * Initially all pages are reserved - free ones are freed

@@ -1510,9 +1648,21 @@ void __init memmap_init_zone(unsigned lo
 {
 	struct page *start = pfn_to_page(start_pfn);
 	struct page *page;
-
+	unsigned long saved_start_pfn = start_pfn;
+	int zoneid = NODEZONE(nid, zone);
+	struct zone *zonep;
+	zonep = zone_table[zoneid];
+
+	if (zonep->memmap_start_pfn == ~0UL) {
+		zonep->memmap_start_pfn = start_pfn;
+	} else if (start_pfn < zonep->memmap_start_pfn) {
+		printk("BUG: memmap is not sorted. \n");
+	}
+	if (zonep->memmap_end_pfn < (start_pfn + size - 1)) {
+		zonep->memmap_end_pfn = start_pfn + size - 1;
+	}
 	for (page = start; page < (start + size); page++) {
-		set_page_zone(page, NODEZONE(nid, zone));
+		set_page_zone(page, zoneid);
 		set_page_count(page, 0);
 		reset_page_mapcount(page);
 		SetPageReserved(page);

@@ -1524,51 +1674,18 @@ void __init memmap_init_zone(unsigned lo
 #endif
 		start_pfn++;
 	}
-}
-
-/*
- * Page buddy system uses "index >> (i+1)", where "index" is
- * at most "size-1".
- *
- * The extra "+3" is to round down to byte size (8 bits per byte
- * assumption). Thus we get "(size-1) >> (i+4)" as the last byte
- * we can access.
- *
- * The "+1" is because we want to round the byte allocation up
- * rather than down. So we should have had a "+7" before we shifted
- * down by three. Also, we have to add one as we actually _use_ the
- * last bit (it's [0,n] inclusive, not [0,n[).
- *
- * So we actually had +7+1 before we shift down by 3. But
- * (n+8) >> 3 == (n >> 3) + 1 (modulo overflows, which we do not have).
- *
- * Finally, we LONG_ALIGN because all bitmap operations are on longs.
- */
-unsigned long pages_to_bitmap_size(unsigned long order, unsigned long nr_pages)
-{
-	unsigned long bitmap_size;
-
-	bitmap_size = (nr_pages-1) >> (order+4);
-	bitmap_size = LONG_ALIGN(bitmap_size+1);
-
-	return bitmap_size;
+	/*
+	 * calling calculate_buddy_range(zone) is to be called per
+	 * a contiguous mem_map.
+	 */
+	calculate_buddy_range(zonep, saved_start_pfn, size);
 }
 
 void zone_init_free_lists(struct pglist_data *pgdat, struct zone *zone, unsigned long size)
 {
 	int order;
-	for (order = 0; ; order++) {
-		unsigned long bitmap_size;
-
+	for (order = 0 ; order < MAX_ORDER ; order++) {
 		INIT_LIST_HEAD(&zone->free_area[order].free_list);
-		if (order == MAX_ORDER-1) {
-			zone->free_area[order].map = NULL;
-			break;
-		}
-
-		bitmap_size = pages_to_bitmap_size(order, size);
-		zone->free_area[order].map =
-		  (unsigned long *) alloc_bootmem_node(pgdat, bitmap_size);
 	}
 }
 

@@ -1682,7 +1799,10 @@ static void __init free_area_init_core(s
 		if ((zone_start_pfn) & (zone_required_alignment-1))
 			printk("BUG: wrong zone alignment, it will crash\n");
 
+		zone->memmap_start_pfn = ~0UL;
+		zone->memmap_end_pfn = 0;
 		memmap_init(size, nid, j, zone_start_pfn);
+		save_end_victim_zone(zone);
 
 		zone_start_pfn += size;
 

diff -puN include/linux/gfp.h~eliminate-bitmap-init include/linux/gfp.h
@@ -5,6 +5,7 @@
 #include <linux/stddef.h>
 #include <linux/linkage.h>
 #include <linux/config.h>
+#include <linux/init.h>
 
 struct vm_area_struct;
 

@@ -124,6 +125,7 @@ extern void FASTCALL(__free_pages(struct
 extern void FASTCALL(free_pages(unsigned long addr, unsigned int order));
 extern void FASTCALL(free_hot_page(struct page *page));
 extern void FASTCALL(free_cold_page(struct page *page));
+extern long __init free_pages_at_init(struct page *base, int order);
 
 #define __free_page(page) __free_pages((page), 0)
 #define free_page(addr) free_pages((addr),0)

diff -puN mm/bootmem.c~eliminate-bitmap-init mm/bootmem.c
@@ -277,7 +277,6 @@ static unsigned long __init free_all_boo
 		if (gofast && v == ~0UL) {
 			int j;
 
-			count += BITS_PER_LONG;
 			__ClearPageReserved(page);
 			set_page_count(page, 1);
 			for (j = 1; j < BITS_PER_LONG; j++) {

@@ -285,17 +284,16 @@ static unsigned long __init free_all_boo
 					prefetchw(page + j + 16);
 				__ClearPageReserved(page + j);
 			}
-			__free_pages(page, ffs(BITS_PER_LONG)-1);
+			count += free_pages_at_init(page,ffs(BITS_PER_LONG)-1);
 			i += BITS_PER_LONG;
 			page += BITS_PER_LONG;
 		} else if (v) {
 			unsigned long m;
 			for (m = 1; m && i < idx; m<<=1, page++, i++) {
 				if (v & m) {
-					count++;
 					__ClearPageReserved(page);
 					set_page_count(page, 1);
-					__free_page(page);
+					count += free_pages_at_init(page,0);
 				}
 			}
 		} else {

@@ -312,10 +310,9 @@ static unsigned long __init free_all_boo
 	page = virt_to_page(bdata->node_bootmem_map);
 	count = 0;
 	for (i = 0; i < ((bdata->node_low_pfn-(bdata->node_boot_start >> PAGE_SHIFT))/8 + PAGE_SIZE-1)/PAGE_SIZE; i++,page++) {
-		count++;
 		__ClearPageReserved(page);
 		set_page_count(page, 1);
-		__free_page(page);
+		count += free_pages_at_init(page,0);
 	}
 	total += count;
 	bdata->node_bootmem_map = NULL;

diff -puN arch/ia64/mm/init.c~eliminate-bitmap-init arch/ia64/mm/init.c
@@ -403,6 +403,8 @@ struct memmap_init_callback_data {
 	unsigned long zone;
 };
 
+/* this is used to avoid to initialize mem_map twice. */
+unsigned long max_initialized_memmap = 0;
 static int
 virtual_memmap_init (u64 start, u64 end, void *arg)
 {

@@ -427,10 +429,13 @@ virtual_memmap_init (u64 start, u64 end,
 	map_start -= ((unsigned long) map_start & (PAGE_SIZE - 1)) / sizeof(struct page);
 	map_end += ((PAGE_ALIGN((unsigned long) map_end) - (unsigned long) map_end)
 		    / sizeof(struct page));
-
-	if (map_start < map_end)
+	if (page_to_pfn(map_start) < max_initialized_memmap)
+		map_start = pfn_to_page(max_initialized_memmap);
+	if (map_start < map_end) {
 		memmap_init_zone((unsigned long)(map_end - map_start),
 				 args->nid, args->zone, page_to_pfn(map_start));
+		max_initialized_memmap = page_to_pfn(map_end) - 1;
+	}
 	return 0;
 }