/*
 *  linux/mm/swap.c
 *
 *  Copyright (C) 1991, 1992, 1993, 1994  Linus Torvalds
 */

/*
 * This file contains the default values for the opereation of the
 * Linux VM subsystem. Fine-tuning documentation can be found in
 * linux/Documentation/sysctl/vm.txt.
 * Started 18.12.91
 * Swap aging added 23.2.95, Stephen Tweedie.
 * Buffermem limits added 12.3.98, Rik van Riel.
 */

#include <linux/mm.h>
#include <linux/kernel_stat.h>
#include <linux/swap.h>
#include <linux/pagemap.h>
#include <linux/pagevec.h>
#include <linux/init.h>
#include <linux/mm_inline.h>
#include <linux/buffer_head.h>
#include <linux/prefetch.h>

/* How many pages do we try to swap or page in/out together? */
int page_cluster;

/*
 * FIXME: speed this up?
 */
void activate_page(struct page *page)
{
        struct zone *zone = page_zone(page);

        spin_lock_irq(&zone->lru_lock);
        if (PageLRU(page) && !PageActive(page)) {
                del_page_from_inactive_list(zone, page);
                SetPageActive(page);
                add_page_to_active_list(zone, page);
                KERNEL_STAT_INC(pgactivate);
        }
        spin_unlock_irq(&zone->lru_lock);
}

/**
 * lru_cache_add: add a page to the page lists
 * @page: the page to add
 */
static struct pagevec lru_add_pvecs[NR_CPUS];

void lru_cache_add(struct page *page)
{
        struct pagevec *pvec = &lru_add_pvecs[get_cpu()];

        page_cache_get(page);
        if (!pagevec_add(pvec, page))
                __pagevec_lru_add(pvec);
        put_cpu();
}

void lru_add_drain(void)
{
        struct pagevec *pvec = &lru_add_pvecs[get_cpu()];

        if (pagevec_count(pvec))
                __pagevec_lru_add(pvec);
        put_cpu();
}

/*
 * This path almost never happens - pages are normally freed via pagevecs.
 */
void __page_cache_release(struct page *page)
{
        unsigned long flags;
        struct zone *zone = page_zone(page);

        spin_lock_irqsave(&zone->lru_lock, flags);
        if (TestClearPageLRU(page))
                del_page_from_lru(zone, page);
        if (page_count(page) != 0)
                page = NULL;
        spin_unlock_irqrestore(&zone->lru_lock, flags);
        if (page)
                __free_pages_ok(page, 0);
}

/*
 * Batched page_cache_release().  Decrement the reference count on all the
 * passed pages.  If it fell to zero then remove the page from the LRU and
 * free it.
 *
 * Avoid taking zone->lru_lock if possible, but if it is taken, retain it
 * for the remainder of the operation.
 *
 * The locking in this function is against shrink_cache(): we recheck the
 * page count inside the lock to see whether shrink_cache grabbed the page
 * via the LRU.  If it did, give up: shrink_cache will free it.
 */
void release_pages(struct page **pages, int nr)
{
        int i;
        struct pagevec pages_to_free;
        struct zone *zone = NULL;

        pagevec_init(&pages_to_free);
        for (i = 0; i < nr; i++) {
                struct page *page = pages[i];
                struct zone *pagezone;

                if (PageReserved(page) || !put_page_testzero(page))
                        continue;

                pagezone = page_zone(page);
                if (pagezone != zone) {
                        if (zone)
                                spin_unlock_irq(&zone->lru_lock);
                        zone = pagezone;
                        spin_lock_irq(&zone->lru_lock);
                }
                if (TestClearPageLRU(page))
                        del_page_from_lru(zone, page);
                if (page_count(page) == 0) {
                        if (!pagevec_add(&pages_to_free, page)) {
                                spin_unlock_irq(&zone->lru_lock);
                                __pagevec_free(&pages_to_free);
                                pagevec_init(&pages_to_free);
                                zone = NULL;    /* No lock is held */
                        }
                }
        }
        if (zone)
                spin_unlock_irq(&zone->lru_lock);

        pagevec_free(&pages_to_free);
}

void __pagevec_release(struct pagevec *pvec)
{
        release_pages(pvec->pages, pagevec_count(pvec));
        pagevec_init(pvec);
}

/*
 * pagevec_release() for pages which are known to not be on the LRU
 *
 * This function reinitialises the caller's pagevec.
 */
void __pagevec_release_nonlru(struct pagevec *pvec)
{
        int i;
        struct pagevec pages_to_free;

        pagevec_init(&pages_to_free);
        for (i = 0; i < pagevec_count(pvec); i++) {
                struct page *page = pvec->pages[i];

                BUG_ON(PageLRU(page));
                if (put_page_testzero(page))
                        pagevec_add(&pages_to_free, page);
        }
        pagevec_free(&pages_to_free);
        pagevec_init(pvec);
}

/*
 * Move all the inactive pages to the head of the inactive list and release
 * them.  Reinitialises the caller's pagevec.
 */
void pagevec_deactivate_inactive(struct pagevec *pvec)
{
        int i;
        struct zone *zone = NULL;

        if (pagevec_count(pvec) == 0)
                return;
        for (i = 0; i < pagevec_count(pvec); i++) {
                struct page *page = pvec->pages[i];
                struct zone *pagezone = page_zone(page);

                if (pagezone != zone) {
                        if (zone)
                                spin_unlock_irq(&zone->lru_lock);
                        zone = pagezone;
                        spin_lock_irq(&zone->lru_lock);
                }
                if (!PageActive(page) && PageLRU(page))
                        list_move(&page->lru, &pagezone->inactive_list);
        }
        if (zone)
                spin_unlock_irq(&zone->lru_lock);
        __pagevec_release(pvec);
}

/*
 * Add the passed pages to the inactive_list, then drop the caller's refcount
 * on them.  Reinitialises the caller's pagevec.
 */
void __pagevec_lru_add(struct pagevec *pvec)
{
        int i;
        struct zone *zone = NULL;

        for (i = 0; i < pagevec_count(pvec); i++) {
                struct page *page = pvec->pages[i];
                struct zone *pagezone = page_zone(page);

                if (pagezone != zone) {
                        if (zone)
                                spin_unlock_irq(&zone->lru_lock);
                        zone = pagezone;
                        spin_lock_irq(&zone->lru_lock);
                }
                if (TestSetPageLRU(page))
                        BUG();
                add_page_to_inactive_list(zone, page);
        }
        if (zone)
                spin_unlock_irq(&zone->lru_lock);
        pagevec_release(pvec);
}

/*
 * Try to drop buffers from the pages in a pagevec
 */
void pagevec_strip(struct pagevec *pvec)
{
        int i;

        for (i = 0; i < pagevec_count(pvec); i++) {
                struct page *page = pvec->pages[i];

                if (PagePrivate(page) && !TestSetPageLocked(page)) {
                        try_to_release_page(page, 0);
                        unlock_page(page);
                }
        }
}

/*
 * Perform any setup for the swap system
 */
void __init swap_setup(void)
{
        unsigned long megs = num_physpages >> (20 - PAGE_SHIFT);

        /* Use a smaller cluster for small-memory machines */
        if (megs < 16)
                page_cluster = 2;
        else
                page_cluster = 3;
        /*
         * Right now other parts of the system means that we
         * _really_ don't want to cluster much more
         */
}