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/*

 * High memory handling common code and variables.

 *

 * (C) 1999 Andrea Arcangeli, SuSE GmbH, andrea@suse.de

 *          Gerhard Wichert, Siemens AG, Gerhard.Wichert@pdb.siemens.de

 *

 *

 * Redesigned the x86 32-bit VM architecture to deal with

 * 64-bit physical space. With current x86 CPUs this

 * means up to 64 Gigabytes physical RAM.

 *

 * Rewrote high memory support to move the page cache into

 * high memory. Implemented permanent (schedulable) kmaps

 * based on Linus' idea.

 *

 * Copyright (C) 1999 Ingo Molnar <mingo@redhat.com>

 */

#include <linux/mm.h>

#include <linux/module.h>

#include <linux/swap.h>

#include <linux/bio.h>

#include <linux/pagemap.h>

#include <linux/mempool.h>

#include <linux/blkdev.h>

#include <linux/init.h>

#include <linux/hash.h>

#include <linux/highmem.h>

#include <linux/blktrace_api.h>

#include <asm/tlbflush.h>

/*

 * Virtual_count is not a pure "count".

 *  0 means that it is not mapped, and has not been mapped

 *    since a TLB flush - it is usable.

 *  1 means that there are no users, but it has been mapped

 *    since the last TLB flush - so we can't use it.

 *  n means that there are (n-1) current users of it.

 */

#ifdef CONFIG_HIGHMEM

unsigned long totalhigh_pages __read_mostly;

unsigned int nr_free_highpages (void)

{

        pg_data_t *pgdat;

        unsigned int pages = 0;

        for_each_online_pgdat(pgdat) {

                pages += zone_page_state(&pgdat->node_zones[ZONE_HIGHMEM],

                        NR_FREE_PAGES);

                if (zone_movable_is_highmem())

                        pages += zone_page_state(

                                        &pgdat->node_zones[ZONE_MOVABLE],

                                        NR_FREE_PAGES);

        }

        return pages;

}

static int pkmap_count[LAST_PKMAP];

static unsigned int last_pkmap_nr;

static  __cacheline_aligned_in_smp DEFINE_SPINLOCK(kmap_lock);

pte_t * pkmap_page_table;

static DECLARE_WAIT_QUEUE_HEAD(pkmap_map_wait);

static void flush_all_zero_pkmaps(void)

{

        int i;

        flush_cache_kmaps();

        for (i = 0; i < LAST_PKMAP; i++) {

                struct page *page;

                /*

                 * zero means we don't have anything to do,

                 * >1 means that it is still in use. Only

                 * a count of 1 means that it is free but

                 * needs to be unmapped

                 */

                if (pkmap_count[i] != 1)

                        continue;

                pkmap_count[i] = 0;

                /* sanity check */

                BUG_ON(pte_none(pkmap_page_table[i]));

                /*

                 * Don't need an atomic fetch-and-clear op here;

                 * no-one has the page mapped, and cannot get at

                 * its virtual address (and hence PTE) without first

                 * getting the kmap_lock (which is held here).

                 * So no dangers, even with speculative execution.

                 */

                page = pte_page(pkmap_page_table[i]);

                pte_clear(&init_mm, (unsigned long)page_address(page),

                          &pkmap_page_table[i]);

                set_page_address(page, NULL);

        }

        flush_tlb_kernel_range(PKMAP_ADDR(0), PKMAP_ADDR(LAST_PKMAP));

}

/* Flush all unused kmap mappings in order to remove stray

   mappings. */

void kmap_flush_unused(void)

{

        spin_lock(&kmap_lock);

        flush_all_zero_pkmaps();

        spin_unlock(&kmap_lock);

}

static inline unsigned long map_new_virtual(struct page *page)

{

        unsigned long vaddr;

        int count;

start:

        count = LAST_PKMAP;

        /* Find an empty entry */

        for (;;) {

                last_pkmap_nr = (last_pkmap_nr + 1) & LAST_PKMAP_MASK;

                if (!last_pkmap_nr) {

                        flush_all_zero_pkmaps();

                        count = LAST_PKMAP;

                }

                if (!pkmap_count[last_pkmap_nr])

                        break;  /* Found a usable entry */

                if (--count)

                        continue;

                /*

                 * Sleep for somebody else to unmap their entries

                 */

                {

                        DECLARE_WAITQUEUE(wait, current);

                        __set_current_state(TASK_UNINTERRUPTIBLE);

                        add_wait_queue(&pkmap_map_wait, &wait);

                        spin_unlock(&kmap_lock);

                        schedule();

                        remove_wait_queue(&pkmap_map_wait, &wait);

                        spin_lock(&kmap_lock);

                        /* Somebody else might have mapped it while we slept */

                        if (page_address(page))

                                return (unsigned long)page_address(page);

                        /* Re-start */

                        goto start;

                }

        }

        vaddr = PKMAP_ADDR(last_pkmap_nr);

        set_pte_at(&init_mm, vaddr,

                   &(pkmap_page_table[last_pkmap_nr]), mk_pte(page, kmap_prot));

        pkmap_count[last_pkmap_nr] = 1;

        set_page_address(page, (void *)vaddr);

        return vaddr;

}

void fastcall *kmap_high(struct page *page)

{

        unsigned long vaddr;

        /*

         * For highmem pages, we can't trust "virtual" until

         * after we have the lock.

         *

         * We cannot call this from interrupts, as it may block

         */

        spin_lock(&kmap_lock);

        vaddr = (unsigned long)page_address(page);

        if (!vaddr)

                vaddr = map_new_virtual(page);

        pkmap_count[PKMAP_NR(vaddr)]++;

        BUG_ON(pkmap_count[PKMAP_NR(vaddr)] < 2);

        spin_unlock(&kmap_lock);

        return (void*) vaddr;

}

EXPORT_SYMBOL(kmap_high);

void fastcall kunmap_high(struct page *page)

{

        unsigned long vaddr;

        unsigned long nr;

        int need_wakeup;

        spin_lock(&kmap_lock);

        vaddr = (unsigned long)page_address(page);

        BUG_ON(!vaddr);

        nr = PKMAP_NR(vaddr);

        /*

         * A count must never go down to zero

         * without a TLB flush!

         */

        need_wakeup = 0;

        switch (--pkmap_count[nr]) {

        case 0:

                BUG();

        case 1:

                /*

                 * Avoid an unnecessary wake_up() function call.

                 * The common case is pkmap_count[] == 1, but

                 * no waiters.

                 * The tasks queued in the wait-queue are guarded

                 * by both the lock in the wait-queue-head and by

                 * the kmap_lock.  As the kmap_lock is held here,

                 * no need for the wait-queue-head's lock.  Simply

                 * test if the queue is empty.

                 */

                need_wakeup = waitqueue_active(&pkmap_map_wait);

        }

        spin_unlock(&kmap_lock);

        /* do wake-up, if needed, race-free outside of the spin lock */

        if (need_wakeup)

                wake_up(&pkmap_map_wait);

}

EXPORT_SYMBOL(kunmap_high);

#endif

#if defined(HASHED_PAGE_VIRTUAL)

#define PA_HASH_ORDER   7

/*

 * Describes one page->virtual association

 */

struct page_address_map {

        struct page *page;

        void *virtual;

        struct list_head list;

};

/*

 * page_address_map freelist, allocated from page_address_maps.

 */

static struct list_head page_address_pool;      /* freelist */

static spinlock_t pool_lock;                    /* protects page_address_pool */

/*

 * Hash table bucket

 */

static struct page_address_slot {

        struct list_head lh;                    /* List of page_address_maps */

        spinlock_t lock;                        /* Protect this bucket's list */

} ____cacheline_aligned_in_smp page_address_htable[1<<PA_HASH_ORDER];

static struct page_address_slot *page_slot(struct page *page)

{

        return &page_address_htable[hash_ptr(page, PA_HASH_ORDER)];

}

void *page_address(struct page *page)

{

        unsigned long flags;

        void *ret;

        struct page_address_slot *pas;

        if (!PageHighMem(page))

                return lowmem_page_address(page);

        pas = page_slot(page);

        ret = NULL;

        spin_lock_irqsave(&pas->lock, flags);

        if (!list_empty(&pas->lh)) {

                struct page_address_map *pam;

                list_for_each_entry(pam, &pas->lh, list) {

                        if (pam->page == page) {

                                ret = pam->virtual;

                                goto done;

                        }

                }

        }

done:

        spin_unlock_irqrestore(&pas->lock, flags);

        return ret;

}

EXPORT_SYMBOL(page_address);

void set_page_address(struct page *page, void *virtual)

{

        unsigned long flags;

        struct page_address_slot *pas;

        struct page_address_map *pam;

        BUG_ON(!PageHighMem(page));

        pas = page_slot(page);

        if (virtual) {          /* Add */

                BUG_ON(list_empty(&page_address_pool));

                spin_lock_irqsave(&pool_lock, flags);

                pam = list_entry(page_address_pool.next,

                                struct page_address_map, list);

                list_del(&pam->list);

                spin_unlock_irqrestore(&pool_lock, flags);

                pam->page = page;

                pam->virtual = virtual;

                spin_lock_irqsave(&pas->lock, flags);

                list_add_tail(&pam->list, &pas->lh);

                spin_unlock_irqrestore(&pas->lock, flags);

        } else {                /* Remove */

                spin_lock_irqsave(&pas->lock, flags);

                list_for_each_entry(pam, &pas->lh, list) {

                        if (pam->page == page) {

                                list_del(&pam->list);

                                spin_unlock_irqrestore(&pas->lock, flags);

                                spin_lock_irqsave(&pool_lock, flags);

                                list_add_tail(&pam->list, &page_address_pool);

                                spin_unlock_irqrestore(&pool_lock, flags);

                                goto done;

                        }

                }

                spin_unlock_irqrestore(&pas->lock, flags);

        }

done:

        return;

}

static struct page_address_map page_address_maps[LAST_PKMAP];

void __init page_address_init(void)

{

        int i;

        INIT_LIST_HEAD(&page_address_pool);

        for (i = 0; i < ARRAY_SIZE(page_address_maps); i++)

                list_add(&page_address_maps[i].list, &page_address_pool);

        for (i = 0; i < ARRAY_SIZE(page_address_htable); i++) {

                INIT_LIST_HEAD(&page_address_htable[i].lh);

                spin_lock_init(&page_address_htable[i].lock);

        }

        spin_lock_init(&pool_lock);

}

#endif  /* defined(CONFIG_HIGHMEM) && !defined(WANT_PAGE_VIRTUAL) */