[mirror_ubuntu-zesty-kernel.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;
}

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);
}

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