[GitHub/mt8127/android_kernel_alcatel_ttab.git] / mm / highmem.c

/*
 * 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/export.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>


#if defined(CONFIG_HIGHMEM) || defined(CONFIG_X86_32)
DEFINE_PER_CPU(int, __kmap_atomic_idx);
#endif

/*
 * 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);


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;
}
EXPORT_SYMBOL_GPL(nr_free_highpages);

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

struct page *kmap_to_page(void *vaddr)
{
	unsigned long addr = (unsigned long)vaddr;

	if (addr >= PKMAP_ADDR(0) && addr < PKMAP_ADDR(LAST_PKMAP)) {
		int i = PKMAP_NR(addr);
		return pte_page(pkmap_page_table[i]);
	}

	return virt_to_page(addr);
}
EXPORT_SYMBOL(kmap_to_page);

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, PKMAP_ADDR(i), &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 - unmap 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;
};

static struct page_address_map page_address_maps[LAST_PKMAP];

/*
 * 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(const 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(const 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 */
		pam = &page_address_maps[PKMAP_NR((unsigned long)virtual)];
		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);
				goto done;
			}
		}
		spin_unlock_irqrestore(&pas->lock, flags);
	}
done:
	return;
}

void __init page_address_init(void)
{
	int i;

	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);
	}
}

#endif	/* defined(CONFIG_HIGHMEM) && !defined(WANT_PAGE_VIRTUAL) */
Commit	Line	Data
1da177e4 LT	1	/*
	2	* High memory handling common code and variables.
	3	*
	4	* (C) 1999 Andrea Arcangeli, SuSE GmbH, andrea@suse.de
	5	* Gerhard Wichert, Siemens AG, Gerhard.Wichert@pdb.siemens.de
	6	*
	7	*
	8	* Redesigned the x86 32-bit VM architecture to deal with
	9	* 64-bit physical space. With current x86 CPUs this
	10	* means up to 64 Gigabytes physical RAM.
	11	*
	12	* Rewrote high memory support to move the page cache into
	13	* high memory. Implemented permanent (schedulable) kmaps
	14	* based on Linus' idea.
	15	*
	16	* Copyright (C) 1999 Ingo Molnar <mingo@redhat.com>
	17	*/
	18
	19	#include <linux/mm.h>
b95f1b31	20	#include <linux/export.h>
1da177e4 LT	21	#include <linux/swap.h>
	22	#include <linux/bio.h>
	23	#include <linux/pagemap.h>
	24	#include <linux/mempool.h>
	25	#include <linux/blkdev.h>
	26	#include <linux/init.h>
	27	#include <linux/hash.h>
	28	#include <linux/highmem.h>
eac79005	29	#include <linux/kgdb.h>
1da177e4 LT	30	#include <asm/tlbflush.h>
1da177e4 LT	31
a8e23a29 PZ	32
	33	#if defined(CONFIG_HIGHMEM) \|\| defined(CONFIG_X86_32)
	34	DEFINE_PER_CPU(int, __kmap_atomic_idx);
	35	#endif
	36
1da177e4 LT	37	/*
	38	* Virtual_count is not a pure "count".
	39	* 0 means that it is not mapped, and has not been mapped
	40	* since a TLB flush - it is usable.
	41	* 1 means that there are no users, but it has been mapped
	42	* since the last TLB flush - so we can't use it.
	43	* n means that there are (n-1) current users of it.
	44	*/
	45	#ifdef CONFIG_HIGHMEM
260b2367	46
c1f60a5a	47	unsigned long totalhigh_pages __read_mostly;
db7a94d6	48	EXPORT_SYMBOL(totalhigh_pages);
c1f60a5a	49
3e4d3af5	50
3e4d3af5 PZ	51	EXPORT_PER_CPU_SYMBOL(__kmap_atomic_idx);
3e4d3af5 PZ	52
c1f60a5a CL	53	unsigned int nr_free_highpages (void)
	54	{
	55	pg_data_t *pgdat;
	56	unsigned int pages = 0;
	57
2a1e274a	58	for_each_online_pgdat(pgdat) {
d23ad423 CL	59	pages += zone_page_state(&pgdat->node_zones[ZONE_HIGHMEM],
d23ad423 CL	60	NR_FREE_PAGES);
2a1e274a MG	61	if (zone_movable_is_highmem())
	62	pages += zone_page_state(
	63	&pgdat->node_zones[ZONE_MOVABLE],
	64	NR_FREE_PAGES);
	65	}
c1f60a5a CL	66
	67	return pages;
	68	}
6fa3eb70	69	EXPORT_SYMBOL_GPL(nr_free_highpages);
c1f60a5a	70
1da177e4 LT	71	static int pkmap_count[LAST_PKMAP];
	72	static unsigned int last_pkmap_nr;
	73	static __cacheline_aligned_in_smp DEFINE_SPINLOCK(kmap_lock);
	74
	75	pte_t * pkmap_page_table;
	76
	77	static DECLARE_WAIT_QUEUE_HEAD(pkmap_map_wait);
	78
3297e760 NP	79	/*
	80	* Most architectures have no use for kmap_high_get(), so let's abstract
	81	* the disabling of IRQ out of the locking in that case to save on a
	82	* potential useless overhead.
	83	*/
	84	#ifdef ARCH_NEEDS_KMAP_HIGH_GET
	85	#define lock_kmap() spin_lock_irq(&kmap_lock)
	86	#define unlock_kmap() spin_unlock_irq(&kmap_lock)
	87	#define lock_kmap_any(flags) spin_lock_irqsave(&kmap_lock, flags)
	88	#define unlock_kmap_any(flags) spin_unlock_irqrestore(&kmap_lock, flags)
	89	#else
	90	#define lock_kmap() spin_lock(&kmap_lock)
	91	#define unlock_kmap() spin_unlock(&kmap_lock)
	92	#define lock_kmap_any(flags) \
	93	do { spin_lock(&kmap_lock); (void)(flags); } while (0)
	94	#define unlock_kmap_any(flags) \
	95	do { spin_unlock(&kmap_lock); (void)(flags); } while (0)
	96	#endif
	97
5a178119 MG	98	struct page kmap_to_page(void vaddr)
	99	{
	100	unsigned long addr = (unsigned long)vaddr;
	101
498c2280	102	if (addr >= PKMAP_ADDR(0) && addr < PKMAP_ADDR(LAST_PKMAP)) {
4de22c05	103	int i = PKMAP_NR(addr);
5a178119 MG	104	return pte_page(pkmap_page_table[i]);
	105	}
	106
	107	return virt_to_page(addr);
	108	}
f0263d2d	109	EXPORT_SYMBOL(kmap_to_page);
5a178119	110
1da177e4 LT	111	static void flush_all_zero_pkmaps(void)
	112	{
	113	int i;
5843d9a4	114	int need_flush = 0;
1da177e4 LT	115
	116	flush_cache_kmaps();
	117
	118	for (i = 0; i < LAST_PKMAP; i++) {
	119	struct page *page;
	120
	121	/*
	122	* zero means we don't have anything to do,
	123	* >1 means that it is still in use. Only
	124	* a count of 1 means that it is free but
	125	* needs to be unmapped
	126	*/
	127	if (pkmap_count[i] != 1)
	128	continue;
	129	pkmap_count[i] = 0;
	130
	131	/* sanity check */
75babcac	132	BUG_ON(pte_none(pkmap_page_table[i]));
1da177e4 LT	133
	134	/*
	135	* Don't need an atomic fetch-and-clear op here;
	136	* no-one has the page mapped, and cannot get at
	137	* its virtual address (and hence PTE) without first
	138	* getting the kmap_lock (which is held here).
	139	* So no dangers, even with speculative execution.
	140	*/
	141	page = pte_page(pkmap_page_table[i]);
eb2db439	142	pte_clear(&init_mm, PKMAP_ADDR(i), &pkmap_page_table[i]);
1da177e4 LT	143
1da177e4 LT	144	set_page_address(page, NULL);
5843d9a4	145	need_flush = 1;
1da177e4	146	}
5843d9a4 NP	147	if (need_flush)
5843d9a4 NP	148	flush_tlb_kernel_range(PKMAP_ADDR(0), PKMAP_ADDR(LAST_PKMAP));
1da177e4 LT	149	}
1da177e4 LT	150
77f6078a RD	151	/**
	152	* kmap_flush_unused - flush all unused kmap mappings in order to remove stray mappings
	153	*/
ce6234b5 JF	154	void kmap_flush_unused(void)
ce6234b5 JF	155	{
3297e760	156	lock_kmap();
ce6234b5	157	flush_all_zero_pkmaps();
3297e760	158	unlock_kmap();
ce6234b5 JF	159	}
ce6234b5 JF	160
1da177e4 LT	161	static inline unsigned long map_new_virtual(struct page *page)
	162	{
	163	unsigned long vaddr;
	164	int count;
	165
	166	start:
	167	count = LAST_PKMAP;
	168	/* Find an empty entry */
	169	for (;;) {
	170	last_pkmap_nr = (last_pkmap_nr + 1) & LAST_PKMAP_MASK;
	171	if (!last_pkmap_nr) {
	172	flush_all_zero_pkmaps();
	173	count = LAST_PKMAP;
	174	}
	175	if (!pkmap_count[last_pkmap_nr])
	176	break; /* Found a usable entry */
	177	if (--count)
	178	continue;
	179
	180	/*
	181	* Sleep for somebody else to unmap their entries
	182	*/
	183	{
	184	DECLARE_WAITQUEUE(wait, current);
	185
	186	__set_current_state(TASK_UNINTERRUPTIBLE);
	187	add_wait_queue(&pkmap_map_wait, &wait);
3297e760	188	unlock_kmap();
1da177e4 LT	189	schedule();
1da177e4 LT	190	remove_wait_queue(&pkmap_map_wait, &wait);
3297e760	191	lock_kmap();
1da177e4 LT	192
	193	/* Somebody else might have mapped it while we slept */
	194	if (page_address(page))
	195	return (unsigned long)page_address(page);
	196
	197	/* Re-start */
	198	goto start;
	199	}
	200	}
	201	vaddr = PKMAP_ADDR(last_pkmap_nr);
	202	set_pte_at(&init_mm, vaddr,
	203	&(pkmap_page_table[last_pkmap_nr]), mk_pte(page, kmap_prot));
	204
	205	pkmap_count[last_pkmap_nr] = 1;
	206	set_page_address(page, (void *)vaddr);
	207
	208	return vaddr;
	209	}
	210
77f6078a RD	211	/**
	212	* kmap_high - map a highmem page into memory
	213	* @page: &struct page to map
	214	*
	215	* Returns the page's virtual memory address.
	216	*
	217	* We cannot call this from interrupts, as it may block.
	218	*/
920c7a5d	219	void kmap_high(struct page page)
1da177e4 LT	220	{
	221	unsigned long vaddr;
	222
	223	/*
	224	* For highmem pages, we can't trust "virtual" until
	225	* after we have the lock.
1da177e4	226	*/
3297e760	227	lock_kmap();
1da177e4 LT	228	vaddr = (unsigned long)page_address(page);
	229	if (!vaddr)
	230	vaddr = map_new_virtual(page);
	231	pkmap_count[PKMAP_NR(vaddr)]++;
75babcac	232	BUG_ON(pkmap_count[PKMAP_NR(vaddr)] < 2);
3297e760	233	unlock_kmap();
1da177e4 LT	234	return (void*) vaddr;
	235	}
	236
	237	EXPORT_SYMBOL(kmap_high);
	238
3297e760 NP	239	#ifdef ARCH_NEEDS_KMAP_HIGH_GET
	240	/**
	241	* kmap_high_get - pin a highmem page into memory
	242	* @page: &struct page to pin
	243	*
	244	* Returns the page's current virtual memory address, or NULL if no mapping
5e39df56	245	* exists. If and only if a non null address is returned then a
3297e760 NP	246	* matching call to kunmap_high() is necessary.
	247	*
	248	* This can be called from any context.
	249	*/
	250	void kmap_high_get(struct page page)
	251	{
	252	unsigned long vaddr, flags;
	253
	254	lock_kmap_any(flags);
	255	vaddr = (unsigned long)page_address(page);
	256	if (vaddr) {
	257	BUG_ON(pkmap_count[PKMAP_NR(vaddr)] < 1);
	258	pkmap_count[PKMAP_NR(vaddr)]++;
	259	}
	260	unlock_kmap_any(flags);
	261	return (void*) vaddr;
	262	}
	263	#endif
	264
77f6078a	265	/**
4e9dc5df	266	* kunmap_high - unmap a highmem page into memory
77f6078a	267	* @page: &struct page to unmap
3297e760 NP	268	*
	269	* If ARCH_NEEDS_KMAP_HIGH_GET is not defined then this may be called
	270	* only from user context.
77f6078a	271	*/
920c7a5d	272	void kunmap_high(struct page *page)
1da177e4 LT	273	{
	274	unsigned long vaddr;
	275	unsigned long nr;
3297e760	276	unsigned long flags;
1da177e4 LT	277	int need_wakeup;
1da177e4 LT	278
3297e760	279	lock_kmap_any(flags);
1da177e4	280	vaddr = (unsigned long)page_address(page);
75babcac	281	BUG_ON(!vaddr);
1da177e4 LT	282	nr = PKMAP_NR(vaddr);
	283
	284	/*
	285	* A count must never go down to zero
	286	* without a TLB flush!
	287	*/
	288	need_wakeup = 0;
	289	switch (--pkmap_count[nr]) {
	290	case 0:
	291	BUG();
	292	case 1:
	293	/*
	294	* Avoid an unnecessary wake_up() function call.
	295	* The common case is pkmap_count[] == 1, but
	296	* no waiters.
	297	* The tasks queued in the wait-queue are guarded
	298	* by both the lock in the wait-queue-head and by
	299	* the kmap_lock. As the kmap_lock is held here,
	300	* no need for the wait-queue-head's lock. Simply
	301	* test if the queue is empty.
	302	*/
	303	need_wakeup = waitqueue_active(&pkmap_map_wait);
	304	}
3297e760	305	unlock_kmap_any(flags);
1da177e4 LT	306
	307	/* do wake-up, if needed, race-free outside of the spin lock */
	308	if (need_wakeup)
	309	wake_up(&pkmap_map_wait);
	310	}
	311
	312	EXPORT_SYMBOL(kunmap_high);
1da177e4 LT	313	#endif
1da177e4 LT	314
1da177e4 LT	315	#if defined(HASHED_PAGE_VIRTUAL)
	316
	317	#define PA_HASH_ORDER 7
	318
	319	/*
	320	* Describes one page->virtual association
	321	*/
	322	struct page_address_map {
	323	struct page *page;
	324	void *virtual;
	325	struct list_head list;
	326	};
	327
a354e2c8	328	static struct page_address_map page_address_maps[LAST_PKMAP];
1da177e4 LT	329
	330	/*
	331	* Hash table bucket
	332	*/
	333	static struct page_address_slot {
	334	struct list_head lh; /* List of page_address_maps */
	335	spinlock_t lock; /* Protect this bucket's list */
	336	} ____cacheline_aligned_in_smp page_address_htable[1<<PA_HASH_ORDER];
	337
f9918794	338	static struct page_address_slot page_slot(const struct page page)
1da177e4 LT	339	{
	340	return &page_address_htable[hash_ptr(page, PA_HASH_ORDER)];
	341	}
	342
77f6078a RD	343	/**
	344	* page_address - get the mapped virtual address of a page
	345	* @page: &struct page to get the virtual address of
	346	*
	347	* Returns the page's virtual address.
	348	*/
f9918794	349	void page_address(const struct page page)
1da177e4 LT	350	{
	351	unsigned long flags;
	352	void *ret;
	353	struct page_address_slot *pas;
	354
	355	if (!PageHighMem(page))
	356	return lowmem_page_address(page);
	357
	358	pas = page_slot(page);
	359	ret = NULL;
	360	spin_lock_irqsave(&pas->lock, flags);
	361	if (!list_empty(&pas->lh)) {
	362	struct page_address_map *pam;
	363
	364	list_for_each_entry(pam, &pas->lh, list) {
	365	if (pam->page == page) {
	366	ret = pam->virtual;
	367	goto done;
	368	}
	369	}
	370	}
	371	done:
	372	spin_unlock_irqrestore(&pas->lock, flags);
	373	return ret;
	374	}
	375
	376	EXPORT_SYMBOL(page_address);
	377
77f6078a RD	378	/**
	379	* set_page_address - set a page's virtual address
	380	* @page: &struct page to set
	381	* @virtual: virtual address to use
	382	*/
1da177e4 LT	383	void set_page_address(struct page page, void virtual)
	384	{
	385	unsigned long flags;
	386	struct page_address_slot *pas;
	387	struct page_address_map *pam;
	388
	389	BUG_ON(!PageHighMem(page));
	390
	391	pas = page_slot(page);
	392	if (virtual) { /* Add */
a354e2c8	393	pam = &page_address_maps[PKMAP_NR((unsigned long)virtual)];
1da177e4 LT	394	pam->page = page;
	395	pam->virtual = virtual;
	396
	397	spin_lock_irqsave(&pas->lock, flags);
	398	list_add_tail(&pam->list, &pas->lh);
	399	spin_unlock_irqrestore(&pas->lock, flags);
	400	} else { /* Remove */
	401	spin_lock_irqsave(&pas->lock, flags);
	402	list_for_each_entry(pam, &pas->lh, list) {
	403	if (pam->page == page) {
	404	list_del(&pam->list);
	405	spin_unlock_irqrestore(&pas->lock, flags);
1da177e4 LT	406	goto done;
	407	}
	408	}
	409	spin_unlock_irqrestore(&pas->lock, flags);
	410	}
	411	done:
	412	return;
	413	}
	414
1da177e4 LT	415	void __init page_address_init(void)
	416	{
	417	int i;
	418
1da177e4 LT	419	for (i = 0; i < ARRAY_SIZE(page_address_htable); i++) {
	420	INIT_LIST_HEAD(&page_address_htable[i].lh);
	421	spin_lock_init(&page_address_htable[i].lock);
	422	}
1da177e4 LT	423	}
	424
	425	#endif /* defined(CONFIG_HIGHMEM) && !defined(WANT_PAGE_VIRTUAL) */