[mirror_ubuntu-bionic-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

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 - 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;
};

/*
 * 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(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 */
		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) */
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
1da177e4 LT	97	static void flush_all_zero_pkmaps(void)
	98	{
	99	int i;
5843d9a4	100	int need_flush = 0;
1da177e4 LT	101
	102	flush_cache_kmaps();
	103
	104	for (i = 0; i < LAST_PKMAP; i++) {
	105	struct page *page;
	106
	107	/*
	108	* zero means we don't have anything to do,
	109	* >1 means that it is still in use. Only
	110	* a count of 1 means that it is free but
	111	* needs to be unmapped
	112	*/
	113	if (pkmap_count[i] != 1)
	114	continue;
	115	pkmap_count[i] = 0;
	116
	117	/* sanity check */
75babcac	118	BUG_ON(pte_none(pkmap_page_table[i]));
1da177e4 LT	119
	120	/*
	121	* Don't need an atomic fetch-and-clear op here;
	122	* no-one has the page mapped, and cannot get at
	123	* its virtual address (and hence PTE) without first
	124	* getting the kmap_lock (which is held here).
	125	* So no dangers, even with speculative execution.
	126	*/
	127	page = pte_page(pkmap_page_table[i]);
	128	pte_clear(&init_mm, (unsigned long)page_address(page),
	129	&pkmap_page_table[i]);
	130
	131	set_page_address(page, NULL);
5843d9a4	132	need_flush = 1;
1da177e4	133	}
5843d9a4 NP	134	if (need_flush)
5843d9a4 NP	135	flush_tlb_kernel_range(PKMAP_ADDR(0), PKMAP_ADDR(LAST_PKMAP));
1da177e4 LT	136	}
1da177e4 LT	137
77f6078a RD	138	/**
	139	* kmap_flush_unused - flush all unused kmap mappings in order to remove stray mappings
	140	*/
ce6234b5 JF	141	void kmap_flush_unused(void)
ce6234b5 JF	142	{
3297e760	143	lock_kmap();
ce6234b5	144	flush_all_zero_pkmaps();
3297e760	145	unlock_kmap();
ce6234b5 JF	146	}
ce6234b5 JF	147
1da177e4 LT	148	static inline unsigned long map_new_virtual(struct page *page)
	149	{
	150	unsigned long vaddr;
	151	int count;
	152
	153	start:
	154	count = LAST_PKMAP;
	155	/* Find an empty entry */
	156	for (;;) {
	157	last_pkmap_nr = (last_pkmap_nr + 1) & LAST_PKMAP_MASK;
	158	if (!last_pkmap_nr) {
	159	flush_all_zero_pkmaps();
	160	count = LAST_PKMAP;
	161	}
	162	if (!pkmap_count[last_pkmap_nr])
	163	break; /* Found a usable entry */
	164	if (--count)
	165	continue;
	166
	167	/*
	168	* Sleep for somebody else to unmap their entries
	169	*/
	170	{
	171	DECLARE_WAITQUEUE(wait, current);
	172
	173	__set_current_state(TASK_UNINTERRUPTIBLE);
	174	add_wait_queue(&pkmap_map_wait, &wait);
3297e760	175	unlock_kmap();
1da177e4 LT	176	schedule();
1da177e4 LT	177	remove_wait_queue(&pkmap_map_wait, &wait);
3297e760	178	lock_kmap();
1da177e4 LT	179
	180	/* Somebody else might have mapped it while we slept */
	181	if (page_address(page))
	182	return (unsigned long)page_address(page);
	183
	184	/* Re-start */
	185	goto start;
	186	}
	187	}
	188	vaddr = PKMAP_ADDR(last_pkmap_nr);
	189	set_pte_at(&init_mm, vaddr,
	190	&(pkmap_page_table[last_pkmap_nr]), mk_pte(page, kmap_prot));
	191
	192	pkmap_count[last_pkmap_nr] = 1;
	193	set_page_address(page, (void *)vaddr);
	194
	195	return vaddr;
	196	}
	197
77f6078a RD	198	/**
	199	* kmap_high - map a highmem page into memory
	200	* @page: &struct page to map
	201	*
	202	* Returns the page's virtual memory address.
	203	*
	204	* We cannot call this from interrupts, as it may block.
	205	*/
920c7a5d	206	void kmap_high(struct page page)
1da177e4 LT	207	{
	208	unsigned long vaddr;
	209
	210	/*
	211	* For highmem pages, we can't trust "virtual" until
	212	* after we have the lock.
1da177e4	213	*/
3297e760	214	lock_kmap();
1da177e4 LT	215	vaddr = (unsigned long)page_address(page);
	216	if (!vaddr)
	217	vaddr = map_new_virtual(page);
	218	pkmap_count[PKMAP_NR(vaddr)]++;
75babcac	219	BUG_ON(pkmap_count[PKMAP_NR(vaddr)] < 2);
3297e760	220	unlock_kmap();
1da177e4 LT	221	return (void*) vaddr;
	222	}
	223
	224	EXPORT_SYMBOL(kmap_high);
	225
3297e760 NP	226	#ifdef ARCH_NEEDS_KMAP_HIGH_GET
	227	/**
	228	* kmap_high_get - pin a highmem page into memory
	229	* @page: &struct page to pin
	230	*
	231	* Returns the page's current virtual memory address, or NULL if no mapping
5e39df56	232	* exists. If and only if a non null address is returned then a
3297e760 NP	233	* matching call to kunmap_high() is necessary.
	234	*
	235	* This can be called from any context.
	236	*/
	237	void kmap_high_get(struct page page)
	238	{
	239	unsigned long vaddr, flags;
	240
	241	lock_kmap_any(flags);
	242	vaddr = (unsigned long)page_address(page);
	243	if (vaddr) {
	244	BUG_ON(pkmap_count[PKMAP_NR(vaddr)] < 1);
	245	pkmap_count[PKMAP_NR(vaddr)]++;
	246	}
	247	unlock_kmap_any(flags);
	248	return (void*) vaddr;
	249	}
	250	#endif
	251
77f6078a	252	/**
4e9dc5df	253	* kunmap_high - unmap a highmem page into memory
77f6078a	254	* @page: &struct page to unmap
3297e760 NP	255	*
	256	* If ARCH_NEEDS_KMAP_HIGH_GET is not defined then this may be called
	257	* only from user context.
77f6078a	258	*/
920c7a5d	259	void kunmap_high(struct page *page)
1da177e4 LT	260	{
	261	unsigned long vaddr;
	262	unsigned long nr;
3297e760	263	unsigned long flags;
1da177e4 LT	264	int need_wakeup;
1da177e4 LT	265
3297e760	266	lock_kmap_any(flags);
1da177e4	267	vaddr = (unsigned long)page_address(page);
75babcac	268	BUG_ON(!vaddr);
1da177e4 LT	269	nr = PKMAP_NR(vaddr);
	270
	271	/*
	272	* A count must never go down to zero
	273	* without a TLB flush!
	274	*/
	275	need_wakeup = 0;
	276	switch (--pkmap_count[nr]) {
	277	case 0:
	278	BUG();
	279	case 1:
	280	/*
	281	* Avoid an unnecessary wake_up() function call.
	282	* The common case is pkmap_count[] == 1, but
	283	* no waiters.
	284	* The tasks queued in the wait-queue are guarded
	285	* by both the lock in the wait-queue-head and by
	286	* the kmap_lock. As the kmap_lock is held here,
	287	* no need for the wait-queue-head's lock. Simply
	288	* test if the queue is empty.
	289	*/
	290	need_wakeup = waitqueue_active(&pkmap_map_wait);
	291	}
3297e760	292	unlock_kmap_any(flags);
1da177e4 LT	293
	294	/* do wake-up, if needed, race-free outside of the spin lock */
	295	if (need_wakeup)
	296	wake_up(&pkmap_map_wait);
	297	}
	298
	299	EXPORT_SYMBOL(kunmap_high);
1da177e4 LT	300	#endif
1da177e4 LT	301
1da177e4 LT	302	#if defined(HASHED_PAGE_VIRTUAL)
	303
	304	#define PA_HASH_ORDER 7
	305
	306	/*
	307	* Describes one page->virtual association
	308	*/
	309	struct page_address_map {
	310	struct page *page;
	311	void *virtual;
	312	struct list_head list;
	313	};
	314
	315	/*
	316	* page_address_map freelist, allocated from page_address_maps.
	317	*/
	318	static struct list_head page_address_pool; /* freelist */
	319	static spinlock_t pool_lock; /* protects page_address_pool */
	320
	321	/*
	322	* Hash table bucket
	323	*/
	324	static struct page_address_slot {
	325	struct list_head lh; /* List of page_address_maps */
	326	spinlock_t lock; /* Protect this bucket's list */
	327	} ____cacheline_aligned_in_smp page_address_htable[1<<PA_HASH_ORDER];
	328
f9918794	329	static struct page_address_slot page_slot(const struct page page)
1da177e4 LT	330	{
	331	return &page_address_htable[hash_ptr(page, PA_HASH_ORDER)];
	332	}
	333
77f6078a RD	334	/**
	335	* page_address - get the mapped virtual address of a page
	336	* @page: &struct page to get the virtual address of
	337	*
	338	* Returns the page's virtual address.
	339	*/
f9918794	340	void page_address(const struct page page)
1da177e4 LT	341	{
	342	unsigned long flags;
	343	void *ret;
	344	struct page_address_slot *pas;
	345
	346	if (!PageHighMem(page))
	347	return lowmem_page_address(page);
	348
	349	pas = page_slot(page);
	350	ret = NULL;
	351	spin_lock_irqsave(&pas->lock, flags);
	352	if (!list_empty(&pas->lh)) {
	353	struct page_address_map *pam;
	354
	355	list_for_each_entry(pam, &pas->lh, list) {
	356	if (pam->page == page) {
	357	ret = pam->virtual;
	358	goto done;
	359	}
	360	}
	361	}
	362	done:
	363	spin_unlock_irqrestore(&pas->lock, flags);
	364	return ret;
	365	}
	366
	367	EXPORT_SYMBOL(page_address);
	368
77f6078a RD	369	/**
	370	* set_page_address - set a page's virtual address
	371	* @page: &struct page to set
	372	* @virtual: virtual address to use
	373	*/
1da177e4 LT	374	void set_page_address(struct page page, void virtual)
	375	{
	376	unsigned long flags;
	377	struct page_address_slot *pas;
	378	struct page_address_map *pam;
	379
	380	BUG_ON(!PageHighMem(page));
	381
	382	pas = page_slot(page);
	383	if (virtual) { /* Add */
	384	BUG_ON(list_empty(&page_address_pool));
	385
	386	spin_lock_irqsave(&pool_lock, flags);
	387	pam = list_entry(page_address_pool.next,
	388	struct page_address_map, list);
	389	list_del(&pam->list);
	390	spin_unlock_irqrestore(&pool_lock, flags);
	391
	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);
	404	spin_lock_irqsave(&pool_lock, flags);
	405	list_add_tail(&pam->list, &page_address_pool);
	406	spin_unlock_irqrestore(&pool_lock, flags);
	407	goto done;
	408	}
	409	}
	410	spin_unlock_irqrestore(&pas->lock, flags);
	411	}
	412	done:
	413	return;
	414	}
	415
	416	static struct page_address_map page_address_maps[LAST_PKMAP];
	417
	418	void __init page_address_init(void)
	419	{
	420	int i;
	421
	422	INIT_LIST_HEAD(&page_address_pool);
	423	for (i = 0; i < ARRAY_SIZE(page_address_maps); i++)
	424	list_add(&page_address_maps[i].list, &page_address_pool);
	425	for (i = 0; i < ARRAY_SIZE(page_address_htable); i++) {
	426	INIT_LIST_HEAD(&page_address_htable[i].lh);
	427	spin_lock_init(&page_address_htable[i].lock);
	428	}
	429	spin_lock_init(&pool_lock);
	430	}
	431
	432	#endif /* defined(CONFIG_HIGHMEM) && !defined(WANT_PAGE_VIRTUAL) */