/*
 *  linux/mm/page_alloc.c
 *
 *  Manages the free list, the system allocates free pages here.
 *  Note that kmalloc() lives in slab.c
 *
 *  Copyright (C) 1991, 1992, 1993, 1994  Linus Torvalds
 *  Swap reorganised 29.12.95, Stephen Tweedie
 *  Support of BIGMEM added by Gerhard Wichert, Siemens AG, July 1999
 *  Reshaped it to be a zoned allocator, Ingo Molnar, Red Hat, 1999
 *  Discontiguous memory support, Kanoj Sarcar, SGI, Nov 1999
 *  Zone balancing, Kanoj Sarcar, SGI, Jan 2000
 */

#include <linux/config.h>
#include <linux/stddef.h>
#include <linux/mm.h>
#include <linux/swap.h>
#include <linux/interrupt.h>
#include <linux/pagemap.h>
#include <linux/bootmem.h>
#include <linux/compiler.h>
#include <linux/module.h>
#include <linux/suspend.h>
#include <linux/pagevec.h>
#include <linux/blkdev.h>
#include <linux/slab.h>

struct pglist_data *pgdat_list;
unsigned long totalram_pages;
unsigned long totalhigh_pages;
int nr_swap_pages;
int numnodes = 1;


/*
 * Used by page_zone() to look up the address of the struct zone whose
 * id is encoded in the upper bits of page->flags
 */
struct zone *zone_table[MAX_NR_ZONES*MAX_NR_NODES];
EXPORT_SYMBOL(zone_table);

static char *zone_names[MAX_NR_ZONES] = { "DMA", "Normal", "HighMem" };
static int zone_balance_ratio[MAX_NR_ZONES] __initdata = { 128, 128, 128, };
static int zone_balance_min[MAX_NR_ZONES] __initdata = { 20 , 20, 20, };
static int zone_balance_max[MAX_NR_ZONES] __initdata = { 255 , 255, 255, };

/*
 * Temporary debugging check for pages not lying within a given zone.
 */
static inline int bad_range(struct zone *zone, struct page *page)
{
	if (page_to_pfn(page) >= zone->zone_start_pfn + zone->spanned_pages)
		return 1;
	if (page_to_pfn(page) < zone->zone_start_pfn)
		return 1;
	if (zone != page_zone(page))
		return 1;
	return 0;
}

/*
 * Freeing function for a buddy system allocator.
 *
 * The concept of a buddy system is to maintain direct-mapped table
 * (containing bit values) for memory blocks of various "orders".
 * The bottom level table contains the map for the smallest allocatable
 * units of memory (here, pages), and each level above it describes
 * pairs of units from the levels below, hence, "buddies".
 * At a high level, all that happens here is marking the table entry
 * at the bottom level available, and propagating the changes upward
 * as necessary, plus some accounting needed to play nicely with other
 * parts of the VM system.
 * At each level, we keep one bit for each pair of blocks, which
 * is set to 1 iff only one of the pair is allocated.  So when we
 * are allocating or freeing one, we can derive the state of the
 * other.  That is, if we allocate a small block, and both were   
 * free, the remainder of the region must be split into blocks.   
 * If a block is freed, and its buddy is also free, then this
 * triggers coalescing into a block of larger size.            
 *
 * -- wli
 */

void __free_pages_ok (struct page *page, unsigned int order)
{
	unsigned long index, page_idx, mask, flags;
	struct free_area *area;
	struct page *base;
	struct zone *zone;

	mod_page_state(pgfree, 1<<order);

	BUG_ON(PageLRU(page));
	BUG_ON(PagePrivate(page));
	BUG_ON(page->mapping != NULL);
	BUG_ON(PageLocked(page));
	BUG_ON(PageActive(page));
	BUG_ON(PageWriteback(page));
	BUG_ON(page->pte.direct != 0);
	if (PageDirty(page))
		ClearPageDirty(page);
	BUG_ON(page_count(page) != 0);

	if (unlikely(current->flags & PF_FREE_PAGES)) {
		if (!current->nr_local_pages && !in_interrupt()) {
			list_add(&page->list, &current->local_pages);
			page->index = order;
			current->nr_local_pages++;
			goto out;
		}
	}

	zone = page_zone(page);

	mask = (~0UL) << order;
	base = zone->zone_mem_map;
	page_idx = page - base;
	if (page_idx & ~mask)
		BUG();
	index = page_idx >> (1 + order);
	area = zone->free_area + order;

	spin_lock_irqsave(&zone->lock, flags);
	zone->free_pages -= mask;
	while (mask + (1 << (MAX_ORDER-1))) {
		struct page *buddy1, *buddy2;

		BUG_ON(area >= zone->free_area + MAX_ORDER);
		if (!__test_and_change_bit(index, area->map))
			/*
			 * the buddy page is still allocated.
			 */
			break;
		/*
		 * Move the buddy up one level.
		 * This code is taking advantage of the identity:
		 * 	-mask = 1+~mask
		 */
		buddy1 = base + (page_idx ^ -mask);
		buddy2 = base + page_idx;
		BUG_ON(bad_range(zone, buddy1));
		BUG_ON(bad_range(zone, buddy2));
		list_del(&buddy1->list);
		mask <<= 1;
		area++;
		index >>= 1;
		page_idx &= mask;
	}
	list_add(&(base + page_idx)->list, &area->free_list);
	spin_unlock_irqrestore(&zone->lock, flags);
out:
	return;
}

#define MARK_USED(index, order, area) \
	__change_bit((index) >> (1+(order)), (area)->map)

static inline struct page *
expand(struct zone *zone, struct page *page,
	 unsigned long index, int low, int high, struct free_area *area)
{
	unsigned long size = 1 << high;

	while (high > low) {
		BUG_ON(bad_range(zone, page));
		area--;
		high--;
		size >>= 1;
		list_add(&page->list, &area->free_list);
		MARK_USED(index, high, area);
		index += size;
		page += size;
	}
	BUG_ON(bad_range(zone, page));
	return page;
}

/*
 * This page is about to be returned from the page allocator
 */
static inline void prep_new_page(struct page *page)
{
	BUG_ON(page->mapping);
	BUG_ON(PagePrivate(page));
	BUG_ON(PageLocked(page));
	BUG_ON(PageLRU(page));
	BUG_ON(PageActive(page));
	BUG_ON(PageDirty(page));
	BUG_ON(PageWriteback(page));
	BUG_ON(page->pte.direct != 0);
	page->flags &= ~(1 << PG_uptodate | 1 << PG_error |
			1 << PG_referenced | 1 << PG_arch_1 |
			1 << PG_checked);
	set_page_count(page, 1);
}

static struct page *rmqueue(struct zone *zone, unsigned int order)
{
	struct free_area *area = zone->free_area + order;
	unsigned int curr_order = order;
	struct list_head *head, *curr;
	unsigned long flags;
	struct page *page;

	spin_lock_irqsave(&zone->lock, flags);
	do {
		head = &area->free_list;
		curr = head->next;

		if (curr != head) {
			unsigned int index;

			page = list_entry(curr, struct page, list);
			BUG_ON(bad_range(zone, page));
			list_del(curr);
			index = page - zone->zone_mem_map;
			if (curr_order != MAX_ORDER-1)
				MARK_USED(index, curr_order, area);
			zone->free_pages -= 1UL << order;

			page = expand(zone, page, index, order, curr_order, area);
			spin_unlock_irqrestore(&zone->lock, flags);

			if (bad_range(zone, page))
				BUG();
			prep_new_page(page);
			return page;	
		}
		curr_order++;
		area++;
	} while (curr_order < MAX_ORDER);
	spin_unlock_irqrestore(&zone->lock, flags);

	return NULL;
}

#ifdef CONFIG_SOFTWARE_SUSPEND
int is_head_of_free_region(struct page *page)
{
        struct zone *zone = page_zone(page);
        unsigned long flags;
	int order;
	struct list_head *curr;

	/*
	 * Should not matter as we need quiescent system for
	 * suspend anyway, but...
	 */
	spin_lock_irqsave(&zone->lock, flags);
	for (order = MAX_ORDER - 1; order >= 0; --order)
		list_for_each(curr, &zone->free_area[order].free_list)
			if (page == list_entry(curr, struct page, list)) {
				spin_unlock_irqrestore(&zone->lock, flags);
				return 1 << order;
			}
	spin_unlock_irqrestore(&zone->lock, flags);
        return 0;
}
#endif /* CONFIG_SOFTWARE_SUSPEND */

static /* inline */ struct page *
balance_classzone(struct zone* classzone, unsigned int gfp_mask,
			unsigned int order, int * freed)
{
	struct page * page = NULL;
	int __freed = 0;

	BUG_ON(in_interrupt());

	current->allocation_order = order;
	current->flags |= PF_MEMALLOC | PF_FREE_PAGES;

	__freed = try_to_free_pages(classzone, gfp_mask, order);

	current->flags &= ~(PF_MEMALLOC | PF_FREE_PAGES);

	if (current->nr_local_pages) {
		struct list_head * entry, * local_pages;
		struct page * tmp;
		int nr_pages;

		local_pages = &current->local_pages;

		if (likely(__freed)) {
			/* pick from the last inserted so we're lifo */
			entry = local_pages->next;
			do {
				tmp = list_entry(entry, struct page, list);
				if (tmp->index == order && memclass(page_zone(tmp), classzone)) {
					list_del(entry);
					page = tmp;
					current->nr_local_pages--;
					prep_new_page(page);
					break;
				}
			} while ((entry = entry->next) != local_pages);
		}

		nr_pages = current->nr_local_pages;
		/* free in reverse order so that the global order will be lifo */
		while ((entry = local_pages->prev) != local_pages) {
			list_del(entry);
			tmp = list_entry(entry, struct page, list);
			__free_pages_ok(tmp, tmp->index);
			if (!nr_pages--)
				BUG();
		}
		current->nr_local_pages = 0;
	}
	*freed = __freed;
	return page;
}

/*
 * This is the 'heart' of the zoned buddy allocator:
 */
struct page *
__alloc_pages(unsigned int gfp_mask, unsigned int order,
		struct zonelist *zonelist)
{
	unsigned long min;
	struct zone **zones, *classzone;
	struct page * page;
	int freed, i;

	if (gfp_mask & __GFP_WAIT)
		might_sleep();

	mod_page_state(pgalloc, 1<<order);

	zones = zonelist->zones;  /* the list of zones suitable for gfp_mask */
	classzone = zones[0]; 
	if (classzone == NULL)    /* no zones in the zonelist */
		return NULL;

	/* Go through the zonelist once, looking for a zone with enough free */
	min = 1UL << order;
	for (i = 0; zones[i] != NULL; i++) {
		struct zone *z = zones[i];

		/* the incremental min is allegedly to discourage fallback */
		min += z->pages_low;
		if (z->free_pages > min || z->free_pages >= z->pages_high) {
			page = rmqueue(z, order);
			if (page)
				return page;
		}
	}

	/* we're somewhat low on memory, failed to find what we needed */
	for (i = 0; zones[i] != NULL; i++) {
		struct zone *z = zones[i];
		if (z->free_pages <= z->pages_low &&
		    waitqueue_active(&z->zone_pgdat->kswapd_wait))
			wake_up_interruptible(&z->zone_pgdat->kswapd_wait);
	}

	/* Go through the zonelist again, taking __GFP_HIGH into account */
	min = 1UL << order;
	for (i = 0; zones[i] != NULL; i++) {
		unsigned long local_min;
		struct zone *z = zones[i];

		local_min = z->pages_min;
		if (gfp_mask & __GFP_HIGH)
			local_min >>= 2;
		min += local_min;
		if (z->free_pages > min || z->free_pages >= z->pages_high) {
			page = rmqueue(z, order);
			if (page)
				return page;
		}
	}

	/* here we're in the low on memory slow path */

rebalance:
	if (current->flags & (PF_MEMALLOC | PF_MEMDIE)) {
		/* go through the zonelist yet again, ignoring mins */
		for (i = 0; zones[i] != NULL; i++) {
			struct zone *z = zones[i];

			page = rmqueue(z, order);
			if (page)
				return page;
		}
nopage:
		if (!(current->flags & PF_NOWARN)) {
			printk("%s: page allocation failure."
				" order:%d, mode:0x%x\n",
				current->comm, order, gfp_mask);
		}
		return NULL;
	}

	/* Atomic allocations - we can't balance anything */
	if (!(gfp_mask & __GFP_WAIT))
		goto nopage;

	inc_page_state(allocstall);
	page = balance_classzone(classzone, gfp_mask, order, &freed);
	if (page)
		return page;

	/* go through the zonelist yet one more time */
	min = 1UL << order;
	for (i = 0; zones[i] != NULL; i++) {
		struct zone *z = zones[i];

		min += z->pages_min;
		if (z->free_pages > min || z->free_pages >= z->pages_high) {
			page = rmqueue(z, order);
			if (page)
				return page;
		}
	}

	/* Don't let big-order allocations loop */
	if (order > 3)
		goto nopage;

	/* Yield for kswapd, and try again */
	yield();
	goto rebalance;
}

/*
 * Common helper functions.
 */
unsigned long __get_free_pages(unsigned int gfp_mask, unsigned int order)
{
	struct page * page;

	page = alloc_pages(gfp_mask, order);
	if (!page)
		return 0;
	return (unsigned long) page_address(page);
}

unsigned long get_zeroed_page(unsigned int gfp_mask)
{
	struct page * page;

	/*
	 * get_zeroed_page() returns a 32-bit address, which cannot represent
	 * a highmem page
	 */
	BUG_ON(gfp_mask & __GFP_HIGHMEM);

	page = alloc_pages(gfp_mask, 0);
	if (page) {
		void *address = page_address(page);
		clear_page(address);
		return (unsigned long) address;
	}
	return 0;
}

void __pagevec_free(struct pagevec *pvec)
{
	int i = pagevec_count(pvec);

	while (--i >= 0)
		__free_pages_ok(pvec->pages[i], 0);
}

void __free_pages(struct page *page, unsigned int order)
{
	if (!PageReserved(page) && put_page_testzero(page))
		__free_pages_ok(page, order);
}

void free_pages(unsigned long addr, unsigned int order)
{
	if (addr != 0) {
		BUG_ON(!virt_addr_valid(addr));
		__free_pages(virt_to_page(addr), order);
	}
}

/*
 * Total amount of free (allocatable) RAM:
 */
unsigned int nr_free_pages(void)
{
	unsigned int sum = 0;
	struct zone *zone;

	for_each_zone(zone)
		sum += zone->free_pages;

	return sum;
}

unsigned int nr_used_zone_pages(void)
{
	unsigned int pages = 0;
	struct zone *zone;

	for_each_zone(zone)
		pages += zone->nr_active + zone->nr_inactive;

	return pages;
}

static unsigned int nr_free_zone_pages(int offset)
{
	pg_data_t *pgdat;
	unsigned int sum = 0;

	for_each_pgdat(pgdat) {
		struct zonelist *zonelist = pgdat->node_zonelists + offset;
		struct zone **zonep = zonelist->zones;
		struct zone *zone;

		for (zone = *zonep++; zone; zone = *zonep++) {
			unsigned long size = zone->present_pages;
			unsigned long high = zone->pages_high;
			if (size > high)
				sum += size - high;
		}
	}

	return sum;
}

/*
 * Amount of free RAM allocatable within ZONE_DMA and ZONE_NORMAL
 */
unsigned int nr_free_buffer_pages(void)
{
	return nr_free_zone_pages(GFP_USER & GFP_ZONEMASK);
}

/*
 * Amount of free RAM allocatable within all zones
 */
unsigned int nr_free_pagecache_pages(void)
{
	return nr_free_zone_pages(GFP_HIGHUSER & GFP_ZONEMASK);
}

#if CONFIG_HIGHMEM
unsigned int nr_free_highpages (void)
{
	pg_data_t *pgdat;
	unsigned int pages = 0;

	for_each_pgdat(pgdat)
		pages += pgdat->node_zones[ZONE_HIGHMEM].free_pages;

	return pages;
}
#endif

/*
 * Accumulate the page_state information across all CPUs.
 * The result is unavoidably approximate - it can change
 * during and after execution of this function.
 */
struct page_state page_states[NR_CPUS] __cacheline_aligned;
EXPORT_SYMBOL(page_states);

void __get_page_state(struct page_state *ret, int nr)
{
	int cpu;

	memset(ret, 0, sizeof(*ret));
	for (cpu = 0; cpu < NR_CPUS; cpu++) {
		unsigned long *in, *out, off;

		if (!cpu_online(cpu))
			continue;

		in = (unsigned long *)(page_states + cpu);
		out = (unsigned long *)ret;
		for (off = 0; off < nr; off++)
			*out++ += *in++;
	}
}

void get_page_state(struct page_state *ret)
{
	int nr;

	nr = offsetof(struct page_state, GET_PAGE_STATE_LAST);
	nr /= sizeof(unsigned long);

	__get_page_state(ret, nr + 1);
}

void get_full_page_state(struct page_state *ret)
{
	__get_page_state(ret, sizeof(*ret) / sizeof(unsigned long));
}

void get_zone_counts(unsigned long *active, unsigned long *inactive)
{
	struct zone *zone;

	*active = 0;
	*inactive = 0;
	for_each_zone(zone) {
		*active += zone->nr_active;
		*inactive += zone->nr_inactive;
	}
}

unsigned long get_page_cache_size(void)
{
	struct page_state ps;

	get_page_state(&ps);
	return ps.nr_pagecache;
}

void si_meminfo(struct sysinfo *val)
{
	val->totalram = totalram_pages;
	val->sharedram = 0;
	val->freeram = nr_free_pages();
	val->bufferram = nr_blockdev_pages();
#ifdef CONFIG_HIGHMEM
	val->totalhigh = totalhigh_pages;
	val->freehigh = nr_free_highpages();
#else
	val->totalhigh = 0;
	val->freehigh = 0;
#endif
	val->mem_unit = PAGE_SIZE;
}

#define K(x) ((x) << (PAGE_SHIFT-10))

/*
 * Show free area list (used inside shift_scroll-lock stuff)
 * We also calculate the percentage fragmentation. We do this by counting the
 * memory on each free list with the exception of the first item on the list.
 */
void show_free_areas(void)
{
	pg_data_t *pgdat;
	struct page_state ps;
	int type;
	unsigned long active;
	unsigned long inactive;

	get_page_state(&ps);
	get_zone_counts(&active, &inactive);

	printk("Free pages:      %6dkB (%6dkB HighMem)\n",
		K(nr_free_pages()),
		K(nr_free_highpages()));

	for (pgdat = pgdat_list; pgdat; pgdat = pgdat->pgdat_next)
		for (type = 0; type < MAX_NR_ZONES; ++type) {
			struct zone *zone = &pgdat->node_zones[type];
			printk("Zone:%s"
				" freepages:%6lukB"
				" min:%6lukB"
				" low:%6lukB"
				" high:%6lukB"
				" active:%6lukB"
				" inactive:%6lukB"
				"\n",
				zone->name,
				K(zone->free_pages),
				K(zone->pages_min),
				K(zone->pages_low),
				K(zone->pages_high),
				K(zone->nr_active),
				K(zone->nr_inactive)
				);
		}

	printk("( Active:%lu inactive:%lu dirty:%lu writeback:%lu free:%u )\n",
		active,
		inactive,
		ps.nr_dirty,
		ps.nr_writeback,
		nr_free_pages());

	for (pgdat = pgdat_list; pgdat; pgdat = pgdat->pgdat_next)
		for (type = 0; type < MAX_NR_ZONES; type++) {
			struct list_head *elem;
			struct zone *zone = &pgdat->node_zones[type];
 			unsigned long nr, flags, order, total = 0;

			if (!zone->present_pages)
				continue;

			spin_lock_irqsave(&zone->lock, flags);
			for (order = 0; order < MAX_ORDER; order++) {
				nr = 0;
				list_for_each(elem, &zone->free_area[order].free_list)
					++nr;
				total += nr << order;
				printk("%lu*%lukB ", nr, K(1UL) << order);
			}
			spin_unlock_irqrestore(&zone->lock, flags);
			printk("= %lukB)\n", K(total));
		}

	show_swap_cache_info();
}

/*
 * Builds allocation fallback zone lists.
 */
static int __init build_zonelists_node(pg_data_t *pgdat, struct zonelist *zonelist, int j, int k)
{
	switch (k) {
		struct zone *zone;
	default:
		BUG();
	case ZONE_HIGHMEM:
		zone = pgdat->node_zones + ZONE_HIGHMEM;
		if (zone->present_pages) {
#ifndef CONFIG_HIGHMEM
			BUG();
#endif
			zonelist->zones[j++] = zone;
		}
	case ZONE_NORMAL:
		zone = pgdat->node_zones + ZONE_NORMAL;
		if (zone->present_pages)
			zonelist->zones[j++] = zone;
	case ZONE_DMA:
		zone = pgdat->node_zones + ZONE_DMA;
		if (zone->present_pages)
			zonelist->zones[j++] = zone;
	}

	return j;
}

static void __init build_zonelists(pg_data_t *pgdat)
{
	int i, j, k, node, local_node;

	local_node = pgdat->node_id;
	printk("Building zonelist for node : %d\n", local_node);
	for (i = 0; i <= GFP_ZONEMASK; i++) {
		struct zonelist *zonelist;

		zonelist = pgdat->node_zonelists + i;
		memset(zonelist, 0, sizeof(*zonelist));

		j = 0;
		k = ZONE_NORMAL;
		if (i & __GFP_HIGHMEM)
			k = ZONE_HIGHMEM;
		if (i & __GFP_DMA)
			k = ZONE_DMA;

 		j = build_zonelists_node(pgdat, zonelist, j, k);
 		/*
 		 * Now we build the zonelist so that it contains the zones
 		 * of all the other nodes.
 		 * We don't want to pressure a particular node, so when
 		 * building the zones for node N, we make sure that the
 		 * zones coming right after the local ones are those from
 		 * node N+1 (modulo N)
 		 */
 		for (node = local_node + 1; node < numnodes; node++)
 			j = build_zonelists_node(NODE_DATA(node), zonelist, j, k);
 		for (node = 0; node < local_node; node++)
 			j = build_zonelists_node(NODE_DATA(node), zonelist, j, k);
 
		zonelist->zones[j++] = NULL;
	} 
}

void __init build_all_zonelists(void)
{
	int i;

	for(i = 0 ; i < numnodes ; i++)
		build_zonelists(NODE_DATA(i));
}

/*
 * Helper functions to size the waitqueue hash table.
 * Essentially these want to choose hash table sizes sufficiently
 * large so that collisions trying to wait on pages are rare.
 * But in fact, the number of active page waitqueues on typical
 * systems is ridiculously low, less than 200. So this is even
 * conservative, even though it seems large.
 *
 * The constant PAGES_PER_WAITQUEUE specifies the ratio of pages to
 * waitqueues, i.e. the size of the waitq table given the number of pages.
 */
#define PAGES_PER_WAITQUEUE	256

static inline unsigned long wait_table_size(unsigned long pages)
{
	unsigned long size = 1;

	pages /= PAGES_PER_WAITQUEUE;

	while (size < pages)
		size <<= 1;

	/*
	 * Once we have dozens or even hundreds of threads sleeping
	 * on IO we've got bigger problems than wait queue collision.
	 * Limit the size of the wait table to a reasonable size.
	 */
	size = min(size, 4096UL);

	return size;
}

/*
 * This is an integer logarithm so that shifts can be used later
 * to extract the more random high bits from the multiplicative
 * hash function before the remainder is taken.
 */
static inline unsigned long wait_table_bits(unsigned long size)
{
	return ffz(~size);
}

#define LONG_ALIGN(x) (((x)+(sizeof(long))-1)&~((sizeof(long))-1))

static void __init calculate_zone_totalpages(struct pglist_data *pgdat,
		unsigned long *zones_size, unsigned long *zholes_size)
{
	unsigned long realtotalpages, totalpages = 0;
	int i;

	for (i = 0; i < MAX_NR_ZONES; i++)
		totalpages += zones_size[i];
	pgdat->node_size = totalpages;

	realtotalpages = totalpages;
	if (zholes_size)
		for (i = 0; i < MAX_NR_ZONES; i++)
			realtotalpages -= zholes_size[i];
	printk("On node %d totalpages: %lu\n", pgdat->node_id, realtotalpages);
}

/*
 * Get space for the valid bitmap.
 */
static void __init calculate_zone_bitmap(struct pglist_data *pgdat,
		unsigned long *zones_size)
{
	unsigned long size = 0;
	int i;

	for (i = 0; i < MAX_NR_ZONES; i++)
		size += zones_size[i];
	size = LONG_ALIGN((size + 7) >> 3);
	pgdat->valid_addr_bitmap = (unsigned long *)alloc_bootmem_node(pgdat, size);
	memset(pgdat->valid_addr_bitmap, 0, size);
}

/*
 * Set up the zone data structures:
 *   - mark all pages reserved
 *   - mark all memory queues empty
 *   - clear the memory bitmaps
 */
static void __init free_area_init_core(struct pglist_data *pgdat,
		unsigned long *zones_size, unsigned long *zholes_size)
{
	unsigned long i, j;
	unsigned long local_offset;
	const unsigned long zone_required_alignment = 1UL << (MAX_ORDER-1);
	int nid = pgdat->node_id;
	struct page *lmem_map = pgdat->node_mem_map;
	unsigned long zone_start_pfn = pgdat->node_start_pfn;

	pgdat->nr_zones = 0;
	init_waitqueue_head(&pgdat->kswapd_wait);
	
	local_offset = 0;                /* offset within lmem_map */
	for (j = 0; j < MAX_NR_ZONES; j++) {
		struct zone *zone = pgdat->node_zones + j;
		unsigned long mask;
		unsigned long size, realsize;

		zone_table[nid * MAX_NR_ZONES + j] = zone;
		realsize = size = zones_size[j];
		if (zholes_size)
			realsize -= zholes_size[j];

		printk("  %s zone: %lu pages\n", zone_names[j], realsize);
		zone->spanned_pages = size;
		zone->present_pages = realsize;
		zone->name = zone_names[j];
		spin_lock_init(&zone->lock);
		spin_lock_init(&zone->lru_lock);
		zone->zone_pgdat = pgdat;
		zone->free_pages = 0;
		INIT_LIST_HEAD(&zone->active_list);
		INIT_LIST_HEAD(&zone->inactive_list);
		atomic_set(&zone->refill_counter, 0);
		zone->nr_active = 0;
		zone->nr_inactive = 0;
		if (!size)
			continue;

		/*
		 * The per-page waitqueue mechanism uses hashed waitqueues
		 * per zone.
		 */
		zone->wait_table_size = wait_table_size(size);
		zone->wait_table_bits =
			wait_table_bits(zone->wait_table_size);
		zone->wait_table = (wait_queue_head_t *)
			alloc_bootmem_node(pgdat, zone->wait_table_size
						* sizeof(wait_queue_head_t));

		for(i = 0; i < zone->wait_table_size; ++i)
			init_waitqueue_head(zone->wait_table + i);

		pgdat->nr_zones = j+1;

		mask = (realsize / zone_balance_ratio[j]);
		if (mask < zone_balance_min[j])
			mask = zone_balance_min[j];
		else if (mask > zone_balance_max[j])
			mask = zone_balance_max[j];
		zone->pages_min = mask;
		zone->pages_low = mask*2;
		zone->pages_high = mask*3;

		zone->zone_mem_map = lmem_map + local_offset;
		zone->zone_start_pfn = zone_start_pfn;

		if ((zone_start_pfn) & (zone_required_alignment-1))
			printk("BUG: wrong zone alignment, it will crash\n");

		/*
		 * Initially all pages are reserved - free ones are freed
		 * up by free_all_bootmem() once the early boot process is
		 * done. Non-atomic initialization, single-pass.
		 */
		for (i = 0; i < size; i++) {
			struct page *page = lmem_map + local_offset + i;
			set_page_zone(page, nid * MAX_NR_ZONES + j);
			set_page_count(page, 0);
			SetPageReserved(page);
			INIT_LIST_HEAD(&page->list);
#ifdef WANT_PAGE_VIRTUAL
			if (j != ZONE_HIGHMEM)
				/*
				 * The shift left won't overflow because the
				 * ZONE_NORMAL is below 4G.
				 */
				set_page_address(page,
					__va(zone_start_pfn << PAGE_SHIFT));
#endif
			zone_start_pfn++;
		}

		local_offset += size;
		for (i = 0; ; i++) {
			unsigned long bitmap_size;

			INIT_LIST_HEAD(&zone->free_area[i].free_list);
			if (i == MAX_ORDER-1) {
				zone->free_area[i].map = NULL;
				break;
			}

			/*
			 * 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.
			 */
			bitmap_size = (size-1) >> (i+4);
			bitmap_size = LONG_ALIGN(bitmap_size+1);
			zone->free_area[i].map = 
			  (unsigned long *) alloc_bootmem_node(pgdat, bitmap_size);
		}
	}
}

void __init free_area_init_node(int nid, struct pglist_data *pgdat,
		struct page *node_mem_map, unsigned long *zones_size,
		unsigned long node_start_pfn, unsigned long *zholes_size)
{
	unsigned long size;

	pgdat->node_id = nid;
	pgdat->node_start_pfn = node_start_pfn;
	calculate_zone_totalpages(pgdat, zones_size, zholes_size);
	if (!node_mem_map) {
		size = (pgdat->node_size + 1) * sizeof(struct page); 
		node_mem_map = alloc_bootmem_node(pgdat, size);
	}
	pgdat->node_mem_map = node_mem_map;

	free_area_init_core(pgdat, zones_size, zholes_size);

	calculate_zone_bitmap(pgdat, zones_size);
}

#ifndef CONFIG_DISCONTIGMEM
static bootmem_data_t contig_bootmem_data;
struct pglist_data contig_page_data = { .bdata = &contig_bootmem_data };

void __init free_area_init(unsigned long *zones_size)
{
	free_area_init_node(0, &contig_page_data, NULL, zones_size, 0, NULL);
	mem_map = contig_page_data.node_mem_map;
}
#endif

static int __init setup_mem_frac(char *str)
{
	int j = 0;

	while (get_option(&str, &zone_balance_ratio[j++]) == 2);
	printk("setup_mem_frac: ");
	for (j = 0; j < MAX_NR_ZONES; j++) printk("%d  ", zone_balance_ratio[j]);
	printk("\n");
	return 1;
}

__setup("memfrac=", setup_mem_frac);

#ifdef CONFIG_PROC_FS

#include <linux/seq_file.h>

static void *frag_start(struct seq_file *m, loff_t *pos)
{
	pg_data_t *pgdat;
	loff_t node = *pos;

	for (pgdat = pgdat_list; pgdat && node; pgdat = pgdat->pgdat_next)
		--node;

	return pgdat;
}

static void *frag_next(struct seq_file *m, void *arg, loff_t *pos)
{
	pg_data_t *pgdat = (pg_data_t *)arg;

	(*pos)++;
	return pgdat->pgdat_next;
}

static void frag_stop(struct seq_file *m, void *arg)
{
}

/* 
 * This walks the freelist for each zone. Whilst this is slow, I'd rather 
 * be slow here than slow down the fast path by keeping stats - mjbligh
 */
static int frag_show(struct seq_file *m, void *arg)
{
	pg_data_t *pgdat = (pg_data_t *)arg;
	struct zone *zone;
	struct zone *node_zones = pgdat->node_zones;
	unsigned long flags;
	int order;

	for (zone = node_zones; zone - node_zones < MAX_NR_ZONES; ++zone) {
		if (!zone->present_pages)
			continue;

		spin_lock_irqsave(&zone->lock, flags);
		seq_printf(m, "Node %d, zone %8s ", pgdat->node_id, zone->name);
		for (order = 0; order < MAX_ORDER; ++order) {
			unsigned long nr_bufs = 0;
			struct list_head *elem;

			list_for_each(elem, &(zone->free_area[order].free_list))
				++nr_bufs;
			seq_printf(m, "%6lu ", nr_bufs);
		}
		spin_unlock_irqrestore(&zone->lock, flags);
		seq_putc(m, '\n');
	}
	return 0;
}

struct seq_operations fragmentation_op = {
	.start	= frag_start,
	.next	= frag_next,
	.stop	= frag_stop,
	.show	= frag_show,
};

static char *vmstat_text[] = {
	"nr_dirty",
	"nr_writeback",
	"nr_pagecache",
	"nr_page_table_pages",
	"nr_reverse_maps",
	"nr_mapped",
	"nr_slab",

	"pgpgin",
	"pgpgout",
	"pswpin",
	"pswpout",
	"pgalloc",
	"pgfree",
	"pgactivate",
	"pgdeactivate",
	"pgfault",
	"pgmajfault",
	"pgscan",
	"pgrefill",
	"pgsteal",
	"kswapd_steal",
	"pageoutrun",
	"allocstall",
};

static void *vmstat_start(struct seq_file *m, loff_t *pos)
{
	struct page_state *ps;

	if (*pos >= ARRAY_SIZE(vmstat_text))
		return NULL;

	ps = kmalloc(sizeof(*ps), GFP_KERNEL);
	m->private = ps;
	if (!ps)
		return ERR_PTR(-ENOMEM);
	get_full_page_state(ps);
	ps->pgpgin /= 2;		/* sectors -> kbytes */
	ps->pgpgout /= 2;
	return (unsigned long *)ps + *pos;
}

static void *vmstat_next(struct seq_file *m, void *arg, loff_t *pos)
{
	(*pos)++;
	if (*pos >= ARRAY_SIZE(vmstat_text))
		return NULL;
	return (unsigned long *)m->private + *pos;
}

static int vmstat_show(struct seq_file *m, void *arg)
{
	unsigned long *l = arg;
	unsigned long off = l - (unsigned long *)m->private;

	seq_printf(m, "%s %lu\n", vmstat_text[off], *l);
	return 0;
}

static void vmstat_stop(struct seq_file *m, void *arg)
{
	kfree(m->private);
	m->private = NULL;
}

struct seq_operations vmstat_op = {
	.start	= vmstat_start,
	.next	= vmstat_next,
	.stop	= vmstat_stop,
	.show	= vmstat_show,
};

#endif /* CONFIG_PROC_FS */
