mm/highmem.c - kernel/msm - Gitiles

 /*
  * 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/kgdb.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;
 EXPORT_SYMBOL(totalhigh_pages);


 DEFINE_PER_CPU(int, __kmap_atomic_idx);
 EXPORT_PER_CPU_SYMBOL(__kmap_atomic_idx);

 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);

 /*
  * Most architectures have no use for kmap_high_get(), so let's abstract
  * the disabling of IRQ out of the locking in that case to save on a
  * potential useless overhead.
  */
 #ifdef ARCH_NEEDS_KMAP_HIGH_GET
 #define lock_kmap()             spin_lock_irq(&kmap_lock)
 #define unlock_kmap()           spin_unlock_irq(&kmap_lock)
 #define lock_kmap_any(flags)    spin_lock_irqsave(&kmap_lock, flags)
 #define unlock_kmap_any(flags)  spin_unlock_irqrestore(&kmap_lock, flags)
 #else
 #define lock_kmap()             spin_lock(&kmap_lock)
 #define unlock_kmap()           spin_unlock(&kmap_lock)
 #define lock_kmap_any(flags)    \
 		do { spin_lock(&kmap_lock); (void)(flags); } while (0)
 #define unlock_kmap_any(flags)  \
 		do { spin_unlock(&kmap_lock); (void)(flags); } while (0)
 #endif

 static void flush_all_zero_pkmaps(void)
 {
 	int i;
 	int need_flush = 0;

 	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);
 		need_flush = 1;
 	}
 	if (need_flush)
 		flush_tlb_kernel_range(PKMAP_ADDR(0), PKMAP_ADDR(LAST_PKMAP));
 }

 /**
  * kmap_flush_unused - flush all unused kmap mappings in order to remove stray mappings
  */
 void kmap_flush_unused(void)
 {
 	lock_kmap();
 	flush_all_zero_pkmaps();
 	unlock_kmap();
 }

 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);
 			unlock_kmap();
 			schedule();
 			remove_wait_queue(&pkmap_map_wait, &wait);
 			lock_kmap();

 			/* 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;
 }

 /**
  * kmap_high - map a highmem page into memory
  * @page: &struct page to map
  *
  * Returns the page's virtual memory address.
  *
  * We cannot call this from interrupts, as it may block.
  */
 void *kmap_high(struct page *page)
 {
 	unsigned long vaddr;

 	/*
 	 * For highmem pages, we can't trust "virtual" until
 	 * after we have the lock.
 	 */
 	lock_kmap();
 	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);
 	unlock_kmap();
 	return (void*) vaddr;
 }

 EXPORT_SYMBOL(kmap_high);

 #ifdef ARCH_NEEDS_KMAP_HIGH_GET
 /**
  * kmap_high_get - pin a highmem page into memory
  * @page: &struct page to pin
  *
  * Returns the page's current virtual memory address, or NULL if no mapping
  * exists.  If and only if a non null address is returned then a
  * matching call to kunmap_high() is necessary.
  *
  * This can be called from any context.
  */
 void *kmap_high_get(struct page *page)
 {
 	unsigned long vaddr, flags;

 	lock_kmap_any(flags);
 	vaddr = (unsigned long)page_address(page);
 	if (vaddr) {
 		BUG_ON(pkmap_count[PKMAP_NR(vaddr)] < 1);
 		pkmap_count[PKMAP_NR(vaddr)]++;
 	}
 	unlock_kmap_any(flags);
 	return (void*) vaddr;
 }
 #endif

 /**
  * kunmap_high - map a highmem page into memory
  * @page: &struct page to unmap
  *
  * If ARCH_NEEDS_KMAP_HIGH_GET is not defined then this may be called
  * only from user context.
  */
 void kunmap_high(struct page *page)
 {
 	unsigned long vaddr;
 	unsigned long nr;
 	unsigned long flags;
 	int need_wakeup;

 	lock_kmap_any(flags);
 	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);
 	}
 	unlock_kmap_any(flags);

 	/* 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)];
 }

 /**
  * page_address - get the mapped virtual address of a page
  * @page: &struct page to get the virtual address of
  *
  * Returns the page's virtual address.
  */
 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);

 /**
  * set_page_address - set a page's virtual address
  * @page: &struct page to set
  * @virtual: virtual address to use
  */
 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) */
	/*
	* 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/kgdb.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;
	EXPORT_SYMBOL(totalhigh_pages);


	DEFINE_PER_CPU(int, __kmap_atomic_idx);
	EXPORT_PER_CPU_SYMBOL(__kmap_atomic_idx);

	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);

	/*
	* Most architectures have no use for kmap_high_get(), so let's abstract
	* the disabling of IRQ out of the locking in that case to save on a
	* potential useless overhead.
	*/
	#ifdef ARCH_NEEDS_KMAP_HIGH_GET
	#define lock_kmap() spin_lock_irq(&kmap_lock)
	#define unlock_kmap() spin_unlock_irq(&kmap_lock)
	#define lock_kmap_any(flags) spin_lock_irqsave(&kmap_lock, flags)
	#define unlock_kmap_any(flags) spin_unlock_irqrestore(&kmap_lock, flags)
	#else
	#define lock_kmap() spin_lock(&kmap_lock)
	#define unlock_kmap() spin_unlock(&kmap_lock)
	#define lock_kmap_any(flags) \
	do { spin_lock(&kmap_lock); (void)(flags); } while (0)
	#define unlock_kmap_any(flags) \
	do { spin_unlock(&kmap_lock); (void)(flags); } while (0)
	#endif

	static void flush_all_zero_pkmaps(void)
	{
	int i;
	int need_flush = 0;

	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);
	need_flush = 1;
	}
	if (need_flush)
	flush_tlb_kernel_range(PKMAP_ADDR(0), PKMAP_ADDR(LAST_PKMAP));
	}

	/**
	* kmap_flush_unused - flush all unused kmap mappings in order to remove stray mappings
	*/
	void kmap_flush_unused(void)
	{
	lock_kmap();
	flush_all_zero_pkmaps();
	unlock_kmap();
	}

	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);
	unlock_kmap();
	schedule();
	remove_wait_queue(&pkmap_map_wait, &wait);
	lock_kmap();

	/* 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;
	}

	/**
	* kmap_high - map a highmem page into memory
	* @page: &struct page to map
	*
	* Returns the page's virtual memory address.
	*
	* We cannot call this from interrupts, as it may block.
	*/
	void kmap_high(struct page page)
	{
	unsigned long vaddr;

	/*
	* For highmem pages, we can't trust "virtual" until
	* after we have the lock.
	*/
	lock_kmap();
	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);
	unlock_kmap();
	return (void*) vaddr;
	}

	EXPORT_SYMBOL(kmap_high);

	#ifdef ARCH_NEEDS_KMAP_HIGH_GET
	/**
	* kmap_high_get - pin a highmem page into memory
	* @page: &struct page to pin
	*
	* Returns the page's current virtual memory address, or NULL if no mapping
	* exists. If and only if a non null address is returned then a
	* matching call to kunmap_high() is necessary.
	*
	* This can be called from any context.
	*/
	void kmap_high_get(struct page page)
	{
	unsigned long vaddr, flags;

	lock_kmap_any(flags);
	vaddr = (unsigned long)page_address(page);
	if (vaddr) {
	BUG_ON(pkmap_count[PKMAP_NR(vaddr)] < 1);
	pkmap_count[PKMAP_NR(vaddr)]++;
	}
	unlock_kmap_any(flags);
	return (void*) vaddr;
	}
	#endif

	/**
	* kunmap_high - map a highmem page into memory
	* @page: &struct page to unmap
	*
	* If ARCH_NEEDS_KMAP_HIGH_GET is not defined then this may be called
	* only from user context.
	*/
	void kunmap_high(struct page *page)
	{
	unsigned long vaddr;
	unsigned long nr;
	unsigned long flags;
	int need_wakeup;

	lock_kmap_any(flags);
	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);
	}
	unlock_kmap_any(flags);

	/* 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)];
	}

	/**
	* page_address - get the mapped virtual address of a page
	* @page: &struct page to get the virtual address of
	*
	* Returns the page's virtual address.
	*/
	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);

	/**
	* set_page_address - set a page's virtual address
	* @page: &struct page to set
	* @virtual: virtual address to use
	*/
	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) */