/*
* 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
* Per cpu hot/cold page lists, bulk allocation, Martin J. Bligh, Sept 2002
* (lots of bits borrowed from Ingo Molnar & Andrew Morton)
*/
#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/kernel.h>
#include <linux/module.h>
#include <linux/suspend.h>
#include <linux/pagevec.h>
#include <linux/blkdev.h>
#include <linux/slab.h>
#include <linux/notifier.h>
#include <linux/topology.h>
#include <linux/sysctl.h>
#include <linux/cpu.h>
#include <linux/cpuset.h>
#include <linux/memory_hotplug.h>
#include <linux/nodemask.h>
#include <linux/vmalloc.h>
#include <linux/mempolicy.h>
#include <asm/tlbflush.h>
#include "internal.h"
/*
* MCD - HACK: Find somewhere to initialize this EARLY, or make this
* initializer cleaner
*/
nodemask_t node_online_map __read_mostly = { { [0] = 1UL } };
EXPORT_SYMBOL(node_online_map);
nodemask_t node_possible_map __read_mostly = NODE_MASK_ALL;
EXPORT_SYMBOL(node_possible_map);
struct pglist_data *pgdat_list __read_mostly;
unsigned long totalram_pages __read_mostly;
unsigned long totalhigh_pages __read_mostly;
long nr_swap_pages;
int percpu_pagelist_fraction;
static void __free_pages_ok(struct page *page, unsigned int order);
/*
* results with 256, 32 in the lowmem_reserve sysctl:
* 1G machine -> (16M dma, 800M-16M normal, 1G-800M high)
* 1G machine -> (16M dma, 784M normal, 224M high)
* NORMAL allocation will leave 784M/256 of ram reserved in the ZONE_DMA
* HIGHMEM allocation will leave 224M/32 of ram reserved in ZONE_NORMAL
* HIGHMEM allocation will (224M+784M)/256 of ram reserved in ZONE_DMA
*
* TBD: should special case ZONE_DMA32 machines here - in those we normally
* don't need any ZONE_NORMAL reservation
*/
int sysctl_lowmem_reserve_ratio[MAX_NR_ZONES-1] = { 256, 256, 32 };
EXPORT_SYMBOL(totalram_pages);
/*
* 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[1 << ZONETABLE_SHIFT] __read_mostly;
EXPORT_SYMBOL(zone_table);
static char *zone_names[MAX_NR_ZONES] = { "DMA", "DMA32", "Normal", "HighMem" };
int min_free_kbytes = 1024;
unsigned long __initdata nr_kernel_pages;
unsigned long __initdata nr_all_pages;
#ifdef CONFIG_DEBUG_VM
static int page_outside_zone_boundaries(struct zone *zone, struct page *page)
{
int ret = 0;
unsigned seq;
unsigned long pfn = page_to_pfn(page);
do {
seq = zone_span_seqbegin(zone);
if (pfn >= zone->zone_start_pfn + zone->spanned_pages)
ret = 1;
else if (pfn < zone->zone_start_pfn)
ret = 1;
} while (zone_span_seqretry(zone, seq));
return ret;
}
static int page_is_consistent(struct zone *zone, struct page *page)
{
#ifdef CONFIG_HOLES_IN_ZONE
if (!pfn_valid(page_to_pfn(page)))
return 0;
#endif
if (zone != page_zone(page))
return 0;
return 1;
}
/*
* Temporary debugging check for pages not lying within a given zone.
*/
static int bad_range(struct zone *zone, struct page *page)
{
if (page_outside_zone_boundaries(zone, page))
return 1;
if (!page_is_consistent(zone, page))
return 1;
return 0;
}
#else
static inline int bad_range(struct zone *zone, struct page *page)
{
return 0;
}
#endif
static void bad_page(struct page *page)
{
printk(KERN_EMERG "Bad page state in process '%s'\n"
KERN_EMERG "page:%p flags:0x%0*lx mapping:%p mapcount:%d count:%d\n"
KERN_EMERG "Trying to fix it up, but a reboot is needed\n"
KERN_EMERG "Backtrace:\n",
current->comm, page, (int)(2*sizeof(unsigned long)),
(unsigned long)page->flags, page->mapping,
page_mapcount(page), page_count(page));
dump_stack();
page->flags &= ~(1 << PG_lru |
1 << PG_private |
1 << PG_locked |
1 << PG_active |
1 << PG_dirty |
1 << PG_reclaim |
1 << PG_slab |
1 << PG_swapcache |
1 << PG_writeback );
set_page_count(page, 0);
reset_page_mapcount(page);
page->mapping = NULL;
add_taint(TAINT_BAD_PAGE);
}
/*
* Higher-order pages are called "compound pages". They are structured thusly:
*
* The first PAGE_SIZE page is called the "head page".
*
* The remaining PAGE_SIZE pages are called "tail pages".
*
* All pages have PG_compound set. All pages have their ->private pointing at
* the head page (even the head page has this).
*
* The first tail page's ->lru.next holds the address of the compound page's
* put_page() function. Its ->lru.prev holds the order of allocation.
* This usage means that zero-order pages may not be compound.
*/
static void free_compound_page(struct page *page)
{
__free_pages_ok(page, (unsigned long)page[1].lru.prev);
}
static void prep_compound_page(struct page *page, unsigned long order)
{
int i;
int nr_pages = 1 << order;
page[1].lru.next = (void *)free_compound_page; /* set dtor */
page[1].lru.prev = (void *)order;
for (i = 0; i < nr_pages; i++) {
struct page *p = page + i;
__SetPageCompound(p);
set_page_private(p, (unsigned long)page);
}
}
static void destroy_compound_page(struct page *page, unsigned long order)
{
int i;
int nr_pages = 1 << order;
if (unlikely((unsigned long)page[1].lru.prev != order))
bad_page(page);
for (i = 0; i < nr_pages; i++) {
struct page *p = page + i;
if (unlikely(!PageCompound(p) |
(page_private(p) != (unsigned long)page)))
bad_page(page);
__ClearPageCompound(p);
}
}
static inline void prep_zero_page(struct page *page, int order, gfp_t gfp_flags)
{
int i;
BUG_ON((gfp_flags & (__GFP_WAIT | __GFP_HIGHMEM)) == __GFP_HIGHMEM);
/*
* clear_highpage() will use KM_USER0, so it's a bug to use __GFP_ZERO
* and __GFP_HIGHMEM from hard or soft interrupt context.
*/
BUG_ON((gfp_flags & __GFP_HIGHMEM) && in_interrupt());
for (i = 0; i < (1 << order); i++)
clear_highpage(page + i);
}
/*
* function for dealing with page's order in buddy system.
* zone->lock is already acquired when we use these.
* So, we don't need atomic page->flags operations here.
*/
static inline unsigned long page_order(struct page *page) {
return page_private(page);
}
static inline void set_page_order(struct page *page, int order) {
set_page_private(page, order);
__SetPagePrivate(page);
}
static inline void rmv_page_order(struct page *page)
{
__ClearPagePrivate(page);
set_page_private(page, 0);
}
/*
* Locate the struct page for both the matching buddy in our
* pair (buddy1) and the combined O(n+1) page they form (page).
*
* 1) Any buddy B1 will have an order O twin B2 which satisfies
* the following equation:
* B2 = B1 ^ (1 << O)
* For example, if the starting buddy (buddy2) is #8 its order
* 1 buddy is #10:
* B2 = 8 ^ (1 << 1) = 8 ^ 2 = 10
*
* 2) Any buddy B will have an order O+1 parent P which
* satisfies the following equation:
* P = B & ~(1 << O)
*
* Assumption: *_mem_map is contigious at least up to MAX_ORDER
*/
static inline struct page *
__page_find_buddy(struct page *page, unsigned long page_idx, unsigned int order)
{
unsigned long buddy_idx = page_idx ^ (1 << order);
return page + (buddy_idx - page_idx);
}
static inline unsigned long
__find_combined_index(unsigned long page_idx, unsigned int order)
{
return (page_idx & ~(1 << order));
}
/*
* This function checks whether a page is free && is the buddy
* we can do coalesce a page and its buddy if
* (a) the buddy is not in a hole &&
* (b) the buddy is free &&
* (c) the buddy is on the buddy system &&
* (d) a page and its buddy have the same order.
* for recording page's order, we use page_private(page) and PG_private.
*
*/
static inline int page_is_buddy(struct page *page, int order)
{
#ifdef CONFIG_HOLES_IN_ZONE
if (!pfn_valid(page_to_pfn(page)))
return 0;
#endif
if (PagePrivate(page) &&
(page_order(page) == order) &&
page_count(page) == 0)
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 a list of pages, which are heads of continuous
* free pages of length of (1 << order) and marked with PG_Private.Page's
* order is recorded in page_private(page) field.
* 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
*/
static inline void __free_one_page(struct page *page,
struct zone *zone, unsigned int order)
{
unsigned long page_idx;
int order_size = 1 << order;
if (unlikely(PageCompound(page)))
destroy_compound_page(page, order);
page_idx = page_to_pfn(page) & ((1 << MAX_ORDER) - 1);
BUG_ON(page_idx & (order_size - 1));
BUG_ON(bad_range(zone, page));
zone->free_pages += order_size;
while (order < MAX_ORDER-1) {
unsigned long combined_idx;
struct free_area *area;
struct page *buddy;
buddy = __page_find_buddy(page, page_idx, order);
if (!page_is_buddy(buddy, order))
break; /* Move the buddy up one level. */
list_del(&buddy->lru);
area = zone->free_area + order;
area->nr_free--;
rmv_page_order(buddy);
combined_idx = __find_combined_index(page_idx, order);
page = page + (combined_idx - page_idx);
page_idx = combined_idx;
order++;
}
set_page_order(page, order);
list_add(&page->lru, &zone->free_area[order].free_list);
zone->free_area[order].nr_free++;
}
static inline int free_pages_check(struct page *page)
{
if (unlikely(page_mapcount(page) |
(page->mapping != NULL) |
(page_count(page) != 0) |
(page->flags & (
1 << PG_lru |
1 << PG_private |
1 << PG_locked |
1 << PG_active |
1 << PG_reclaim |
1 << PG_slab |
1 << PG_swapcache |
1 << PG_writeback |
1 << PG_reserved ))))
bad_page(page);
if (PageDirty(page))
__ClearPageDirty(page);
/*
* For now, we report if PG_reserved was found set, but do not
* clear it, and do not free the page. But we shall soon need
* to do more, for when the ZERO_PAGE count wraps negative.
*/
return PageReserved(page);
}
/*
* Frees a list of pages.
* Assumes all pages on list are in same zone, and of same order.
* count is the number of pages to free.
*
* If the zone was previously in an "all pages pinned" state then look to
* see if this freeing clears that state.
*
* And clear the zone's pages_scanned counter, to hold off the "all pages are
* pinned" detection logic.
*/
static void free_pages_bulk(struct zone *zone, int count,
struct list_head *list, int order)
{
spin_lock(&zone->lock);
zone->all_unreclaimable = 0;
zone->pages_scanned = 0;
while (count--) {
struct page *page;
BUG_ON(list_empty(list));
page = list_entry(list->prev, struct page, lru);
/* have to delete it as __free_one_page list manipulates */
list_del(&page->lru);
__free_one_page(page, zone, order);
}
spin_unlock(&zone->lock);
}
static void free_one_page(struct zone *zone, struct page *page, int order)
{
LIST_HEAD(list);
list_add(&page->lru, &list);
free_pages_bulk(zone, 1, &list, order);
}
static void __free_pages_ok(struct page *page, unsigned int order)
{
unsigned long flags;
int i;
int reserved = 0;
arch_free_page(page, order);
if (!PageHighMem(page))
mutex_debug_check_no_locks_freed(page_address(page),
PAGE_SIZE<<order);
for (i = 0 ; i < (1 << order) ; ++i)
reserved += free_pages_check(page + i);
if (reserved)
return;
kernel_map_pages(page, 1 << order, 0);
local_irq_save(flags);
__mod_page_state(pgfree, 1 << order);
free_one_page(page_zone(page), page, order);
local_irq_restore(flags);
}
/*
* permit the bootmem allocator to evade page validation on high-order frees
*/
void fastcall __init __free_pages_bootmem(struct page *page, unsigned int order)
{
if (order == 0) {
__ClearPageReserved(page);
set_page_count(page, 0);
set_page_refcounted(page);
__free_page(page);
} else {
int loop;
prefetchw(page);
for (loop = 0; loop < BITS_PER_LONG; loop++) {
struct page *p = &page[loop];
if (loop + 1 < BITS_PER_LONG)
prefetchw(p + 1);
__ClearPageReserved(p);
set_page_count(p, 0);
}
set_page_refcounted(page);
__free_pages(page, order);
}
}
/*
* The order of subdivision here is critical for the IO subsystem.
* Please do not alter this order without good reasons and regression
* testing. Specifically, as large blocks of memory are subdivided,
* the order in which smaller blocks are delivered depends on the order
* they're subdivided in this function. This is the primary factor
* influencing the order in which pages are delivered to the IO
* subsystem according to empirical testing, and this is also justified
* by considering the behavior of a buddy system containing a single
* large block of memory acted on by a series of small allocations.
* This behavior is a critical factor in sglist merging's success.
*
* -- wli
*/
static inline void expand(struct zone *zone, struct page *page,
int low, int high, struct free_area *area)
{
unsigned long size = 1 << high;
while (high > low) {
area--;
high--;
size >>= 1;
BUG_ON(bad_range(zone, &page[size]));
list_add(&page[size].lru, &area->free_list);
area->nr_free++;
set_page_order(&page[size], high);
}
}
/*
* This page is about to be returned from the page allocator
*/
static int prep_new_page(struct page *page, int order, gfp_t gfp_flags)
{
if (unlikely(page_mapcount(page) |
(page->mapping != NULL) |
(page_count(page) != 0) |
(page->flags & (
1 << PG_lru |
1 << PG_private |
1 << PG_locked |
1 << PG_active |
1 << PG_dirty |
1 << PG_reclaim |
1 << PG_slab |
1 << PG_swapcache |
1 << PG_writeback |
1 << PG_reserved ))))
bad_page(page);
/*
* For now, we report if PG_reserved was found set, but do not
* clear it, and do not allocate the page: as a safety net.
*/
if (PageReserved(page))
return 1;
page->flags &= ~(1 << PG_uptodate | 1 << PG_error |
1 << PG_referenced | 1 << PG_arch_1 |
1 << PG_checked | 1 << PG_mappedtodisk);
set_page_private(page, 0);
set_page_refcounted(page);
kernel_map_pages(page, 1 << order, 1);
if (gfp_flags & __GFP_ZERO)
prep_zero_page(page, order, gfp_flags);
if (order && (gfp_flags & __GFP_COMP))
prep_compound_page(page, order);
return 0;
}
/*
* Do the hard work of removing an element from the buddy allocator.
* Call me with the zone->lock already held.
*/
static struct page *__rmqueue(struct zone *zone, unsigned int order)
{
struct free_area * area;
unsigned int current_order;
struct page *page;
for (current_order = order; current_order < MAX_ORDER; ++current_order) {
area = zone->free_area + current_order;
if (list_empty(&area->free_list))
continue;
page = list_entry(area->free_list.next, struct page, lru);
list_del(&page->lru);
rmv_page_order(page);
area->nr_free--;
zone->free_pages -= 1UL << order;
expand(zone, page, order, current_order, area);
return page;
}
return NULL;
}
/*
* Obtain a specified number of elements from the buddy allocator, all under
* a single hold of the lock, for efficiency. Add them to the supplied list.
* Returns the number of new pages which were placed at *list.
*/
static int rmqueue_bulk(struct zone *zone, unsigned int order,
unsigned long count, struct list_head *list)
{
int i;
spin_lock(&zone->lock);
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