[linux.git] / mm / highmem.c

/*
 * High memory handling common code and variables.
 *
 * (C) 1999 Andrea Arcangeli, SuSE GmbH, [email protected]
 *          Gerhard Wichert, Siemens AG, [email protected]
 *
 *
 * 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 <[email protected]>
 */

#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;
}

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