[linux-block.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/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 <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);

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.  When and only when 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) */

#if defined(CONFIG_DEBUG_HIGHMEM) && defined(CONFIG_TRACE_IRQFLAGS_SUPPORT)

void debug_kmap_atomic(enum km_type type)
{
	static unsigned warn_count = 10;

	if (unlikely(warn_count == 0))
		return;

	if (unlikely(in_interrupt())) {
		if (in_irq()) {
			if (type != KM_IRQ0 && type != KM_IRQ1 &&
			    type != KM_BIO_SRC_IRQ && type != KM_BIO_DST_IRQ &&
			    type != KM_BOUNCE_READ) {
				WARN_ON(1);
				warn_count--;
			}
		} else if (!irqs_disabled()) {	/* softirq */
			if (type != KM_IRQ0 && type != KM_IRQ1 &&
			    type != KM_SOFTIRQ0 && type != KM_SOFTIRQ1 &&
			    type != KM_SKB_SUNRPC_DATA &&
			    type != KM_SKB_DATA_SOFTIRQ &&
			    type != KM_BOUNCE_READ) {
				WARN_ON(1);
				warn_count--;
			}
		}
	}

	if (type == KM_IRQ0 || type == KM_IRQ1 || type == KM_BOUNCE_READ ||
			type == KM_BIO_SRC_IRQ || type == KM_BIO_DST_IRQ) {
		if (!irqs_disabled()) {
			WARN_ON(1);
			warn_count--;
		}
	} else if (type == KM_SOFTIRQ0 || type == KM_SOFTIRQ1) {
		if (irq_count() == 0 && !irqs_disabled()) {
			WARN_ON(1);
			warn_count--;
		}
	}
}

#endif
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>
	20	#include <linux/module.h>
	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>
	29	#include <asm/tlbflush.h>
	30
1da177e4 LT	31	/*
	32	* Virtual_count is not a pure "count".
	33	* 0 means that it is not mapped, and has not been mapped
	34	* since a TLB flush - it is usable.
	35	* 1 means that there are no users, but it has been mapped
	36	* since the last TLB flush - so we can't use it.
	37	* n means that there are (n-1) current users of it.
	38	*/
	39	#ifdef CONFIG_HIGHMEM
260b2367	40
c1f60a5a	41	unsigned long totalhigh_pages __read_mostly;
db7a94d6	42	EXPORT_SYMBOL(totalhigh_pages);
c1f60a5a CL	43
	44	unsigned int nr_free_highpages (void)
	45	{
	46	pg_data_t *pgdat;
	47	unsigned int pages = 0;
	48
2a1e274a	49	for_each_online_pgdat(pgdat) {
d23ad423 CL	50	pages += zone_page_state(&pgdat->node_zones[ZONE_HIGHMEM],
d23ad423 CL	51	NR_FREE_PAGES);
2a1e274a MG	52	if (zone_movable_is_highmem())
	53	pages += zone_page_state(
	54	&pgdat->node_zones[ZONE_MOVABLE],
	55	NR_FREE_PAGES);
	56	}
c1f60a5a CL	57
	58	return pages;
	59	}
	60
1da177e4 LT	61	static int pkmap_count[LAST_PKMAP];
	62	static unsigned int last_pkmap_nr;
	63	static __cacheline_aligned_in_smp DEFINE_SPINLOCK(kmap_lock);
	64
	65	pte_t * pkmap_page_table;
	66
	67	static DECLARE_WAIT_QUEUE_HEAD(pkmap_map_wait);
	68
3297e760 NP	69	/*
	70	* Most architectures have no use for kmap_high_get(), so let's abstract
	71	* the disabling of IRQ out of the locking in that case to save on a
	72	* potential useless overhead.
	73	*/
	74	#ifdef ARCH_NEEDS_KMAP_HIGH_GET
	75	#define lock_kmap() spin_lock_irq(&kmap_lock)
	76	#define unlock_kmap() spin_unlock_irq(&kmap_lock)
	77	#define lock_kmap_any(flags) spin_lock_irqsave(&kmap_lock, flags)
	78	#define unlock_kmap_any(flags) spin_unlock_irqrestore(&kmap_lock, flags)
	79	#else
	80	#define lock_kmap() spin_lock(&kmap_lock)
	81	#define unlock_kmap() spin_unlock(&kmap_lock)
	82	#define lock_kmap_any(flags) \
	83	do { spin_lock(&kmap_lock); (void)(flags); } while (0)
	84	#define unlock_kmap_any(flags) \
	85	do { spin_unlock(&kmap_lock); (void)(flags); } while (0)
	86	#endif
	87
1da177e4 LT	88	static void flush_all_zero_pkmaps(void)
	89	{
	90	int i;
5843d9a4	91	int need_flush = 0;
1da177e4 LT	92
	93	flush_cache_kmaps();
	94
	95	for (i = 0; i < LAST_PKMAP; i++) {
	96	struct page *page;
	97
	98	/*
	99	* zero means we don't have anything to do,
	100	* >1 means that it is still in use. Only
	101	* a count of 1 means that it is free but
	102	* needs to be unmapped
	103	*/
	104	if (pkmap_count[i] != 1)
	105	continue;
	106	pkmap_count[i] = 0;
	107
	108	/* sanity check */
75babcac	109	BUG_ON(pte_none(pkmap_page_table[i]));
1da177e4 LT	110
	111	/*
	112	* Don't need an atomic fetch-and-clear op here;
	113	* no-one has the page mapped, and cannot get at
	114	* its virtual address (and hence PTE) without first
	115	* getting the kmap_lock (which is held here).
	116	* So no dangers, even with speculative execution.
	117	*/
	118	page = pte_page(pkmap_page_table[i]);
	119	pte_clear(&init_mm, (unsigned long)page_address(page),
	120	&pkmap_page_table[i]);
	121
	122	set_page_address(page, NULL);
5843d9a4	123	need_flush = 1;
1da177e4	124	}
5843d9a4 NP	125	if (need_flush)
5843d9a4 NP	126	flush_tlb_kernel_range(PKMAP_ADDR(0), PKMAP_ADDR(LAST_PKMAP));
1da177e4 LT	127	}
1da177e4 LT	128
77f6078a RD	129	/**
	130	* kmap_flush_unused - flush all unused kmap mappings in order to remove stray mappings
	131	*/
ce6234b5 JF	132	void kmap_flush_unused(void)
ce6234b5 JF	133	{
3297e760	134	lock_kmap();
ce6234b5	135	flush_all_zero_pkmaps();
3297e760	136	unlock_kmap();
ce6234b5 JF	137	}
ce6234b5 JF	138
1da177e4 LT	139	static inline unsigned long map_new_virtual(struct page *page)
	140	{
	141	unsigned long vaddr;
	142	int count;
	143
	144	start:
	145	count = LAST_PKMAP;
	146	/* Find an empty entry */
	147	for (;;) {
	148	last_pkmap_nr = (last_pkmap_nr + 1) & LAST_PKMAP_MASK;
	149	if (!last_pkmap_nr) {
	150	flush_all_zero_pkmaps();
	151	count = LAST_PKMAP;
	152	}
	153	if (!pkmap_count[last_pkmap_nr])
	154	break; /* Found a usable entry */
	155	if (--count)
	156	continue;
	157
	158	/*
	159	* Sleep for somebody else to unmap their entries
	160	*/
	161	{
	162	DECLARE_WAITQUEUE(wait, current);
	163
	164	__set_current_state(TASK_UNINTERRUPTIBLE);
	165	add_wait_queue(&pkmap_map_wait, &wait);
3297e760	166	unlock_kmap();
1da177e4 LT	167	schedule();
1da177e4 LT	168	remove_wait_queue(&pkmap_map_wait, &wait);
3297e760	169	lock_kmap();
1da177e4 LT	170
	171	/* Somebody else might have mapped it while we slept */
	172	if (page_address(page))
	173	return (unsigned long)page_address(page);
	174
	175	/* Re-start */
	176	goto start;
	177	}
	178	}
	179	vaddr = PKMAP_ADDR(last_pkmap_nr);
	180	set_pte_at(&init_mm, vaddr,
	181	&(pkmap_page_table[last_pkmap_nr]), mk_pte(page, kmap_prot));
	182
	183	pkmap_count[last_pkmap_nr] = 1;
	184	set_page_address(page, (void *)vaddr);
	185
	186	return vaddr;
	187	}
	188
77f6078a RD	189	/**
	190	* kmap_high - map a highmem page into memory
	191	* @page: &struct page to map
	192	*
	193	* Returns the page's virtual memory address.
	194	*
	195	* We cannot call this from interrupts, as it may block.
	196	*/
920c7a5d	197	void kmap_high(struct page page)
1da177e4 LT	198	{
	199	unsigned long vaddr;
	200
	201	/*
	202	* For highmem pages, we can't trust "virtual" until
	203	* after we have the lock.
1da177e4	204	*/
3297e760	205	lock_kmap();
1da177e4 LT	206	vaddr = (unsigned long)page_address(page);
	207	if (!vaddr)
	208	vaddr = map_new_virtual(page);
	209	pkmap_count[PKMAP_NR(vaddr)]++;
75babcac	210	BUG_ON(pkmap_count[PKMAP_NR(vaddr)] < 2);
3297e760	211	unlock_kmap();
1da177e4 LT	212	return (void*) vaddr;
	213	}
	214
	215	EXPORT_SYMBOL(kmap_high);
	216
3297e760 NP	217	#ifdef ARCH_NEEDS_KMAP_HIGH_GET
	218	/**
	219	* kmap_high_get - pin a highmem page into memory
	220	* @page: &struct page to pin
	221	*
	222	* Returns the page's current virtual memory address, or NULL if no mapping
	223	* exists. When and only when a non null address is returned then a
	224	* matching call to kunmap_high() is necessary.
	225	*
	226	* This can be called from any context.
	227	*/
	228	void kmap_high_get(struct page page)
	229	{
	230	unsigned long vaddr, flags;
	231
	232	lock_kmap_any(flags);
	233	vaddr = (unsigned long)page_address(page);
	234	if (vaddr) {
	235	BUG_ON(pkmap_count[PKMAP_NR(vaddr)] < 1);
	236	pkmap_count[PKMAP_NR(vaddr)]++;
	237	}
	238	unlock_kmap_any(flags);
	239	return (void*) vaddr;
	240	}
	241	#endif
	242
77f6078a RD	243	/**
	244	* kunmap_high - map a highmem page into memory
	245	* @page: &struct page to unmap
3297e760 NP	246	*
	247	* If ARCH_NEEDS_KMAP_HIGH_GET is not defined then this may be called
	248	* only from user context.
77f6078a	249	*/
920c7a5d	250	void kunmap_high(struct page *page)
1da177e4 LT	251	{
	252	unsigned long vaddr;
	253	unsigned long nr;
3297e760	254	unsigned long flags;
1da177e4 LT	255	int need_wakeup;
1da177e4 LT	256
3297e760	257	lock_kmap_any(flags);
1da177e4	258	vaddr = (unsigned long)page_address(page);
75babcac	259	BUG_ON(!vaddr);
1da177e4 LT	260	nr = PKMAP_NR(vaddr);
	261
	262	/*
	263	* A count must never go down to zero
	264	* without a TLB flush!
	265	*/
	266	need_wakeup = 0;
	267	switch (--pkmap_count[nr]) {
	268	case 0:
	269	BUG();
	270	case 1:
	271	/*
	272	* Avoid an unnecessary wake_up() function call.
	273	* The common case is pkmap_count[] == 1, but
	274	* no waiters.
	275	* The tasks queued in the wait-queue are guarded
	276	* by both the lock in the wait-queue-head and by
	277	* the kmap_lock. As the kmap_lock is held here,
	278	* no need for the wait-queue-head's lock. Simply
	279	* test if the queue is empty.
	280	*/
	281	need_wakeup = waitqueue_active(&pkmap_map_wait);
	282	}
3297e760	283	unlock_kmap_any(flags);
1da177e4 LT	284
	285	/* do wake-up, if needed, race-free outside of the spin lock */
	286	if (need_wakeup)
	287	wake_up(&pkmap_map_wait);
	288	}
	289
	290	EXPORT_SYMBOL(kunmap_high);
1da177e4 LT	291	#endif
1da177e4 LT	292
1da177e4 LT	293	#if defined(HASHED_PAGE_VIRTUAL)
	294
	295	#define PA_HASH_ORDER 7
	296
	297	/*
	298	* Describes one page->virtual association
	299	*/
	300	struct page_address_map {
	301	struct page *page;
	302	void *virtual;
	303	struct list_head list;
	304	};
	305
	306	/*
	307	* page_address_map freelist, allocated from page_address_maps.
	308	*/
	309	static struct list_head page_address_pool; /* freelist */
	310	static spinlock_t pool_lock; /* protects page_address_pool */
	311
	312	/*
	313	* Hash table bucket
	314	*/
	315	static struct page_address_slot {
	316	struct list_head lh; /* List of page_address_maps */
	317	spinlock_t lock; /* Protect this bucket's list */
	318	} ____cacheline_aligned_in_smp page_address_htable[1<<PA_HASH_ORDER];
	319
	320	static struct page_address_slot page_slot(struct page page)
	321	{
	322	return &page_address_htable[hash_ptr(page, PA_HASH_ORDER)];
	323	}
	324
77f6078a RD	325	/**
	326	* page_address - get the mapped virtual address of a page
	327	* @page: &struct page to get the virtual address of
	328	*
	329	* Returns the page's virtual address.
	330	*/
1da177e4 LT	331	void page_address(struct page page)
	332	{
	333	unsigned long flags;
	334	void *ret;
	335	struct page_address_slot *pas;
	336
	337	if (!PageHighMem(page))
	338	return lowmem_page_address(page);
	339
	340	pas = page_slot(page);
	341	ret = NULL;
	342	spin_lock_irqsave(&pas->lock, flags);
	343	if (!list_empty(&pas->lh)) {
	344	struct page_address_map *pam;
	345
	346	list_for_each_entry(pam, &pas->lh, list) {
	347	if (pam->page == page) {
	348	ret = pam->virtual;
	349	goto done;
	350	}
	351	}
	352	}
	353	done:
	354	spin_unlock_irqrestore(&pas->lock, flags);
	355	return ret;
	356	}
	357
	358	EXPORT_SYMBOL(page_address);
	359
77f6078a RD	360	/**
	361	* set_page_address - set a page's virtual address
	362	* @page: &struct page to set
	363	* @virtual: virtual address to use
	364	*/
1da177e4 LT	365	void set_page_address(struct page page, void virtual)
	366	{
	367	unsigned long flags;
	368	struct page_address_slot *pas;
	369	struct page_address_map *pam;
	370
	371	BUG_ON(!PageHighMem(page));
	372
	373	pas = page_slot(page);
	374	if (virtual) { /* Add */
	375	BUG_ON(list_empty(&page_address_pool));
	376
	377	spin_lock_irqsave(&pool_lock, flags);
	378	pam = list_entry(page_address_pool.next,
	379	struct page_address_map, list);
	380	list_del(&pam->list);
	381	spin_unlock_irqrestore(&pool_lock, flags);
	382
	383	pam->page = page;
	384	pam->virtual = virtual;
	385
	386	spin_lock_irqsave(&pas->lock, flags);
	387	list_add_tail(&pam->list, &pas->lh);
	388	spin_unlock_irqrestore(&pas->lock, flags);
	389	} else { /* Remove */
	390	spin_lock_irqsave(&pas->lock, flags);
	391	list_for_each_entry(pam, &pas->lh, list) {
	392	if (pam->page == page) {
	393	list_del(&pam->list);
	394	spin_unlock_irqrestore(&pas->lock, flags);
	395	spin_lock_irqsave(&pool_lock, flags);
	396	list_add_tail(&pam->list, &page_address_pool);
	397	spin_unlock_irqrestore(&pool_lock, flags);
	398	goto done;
	399	}
	400	}
	401	spin_unlock_irqrestore(&pas->lock, flags);
	402	}
	403	done:
	404	return;
	405	}
	406
	407	static struct page_address_map page_address_maps[LAST_PKMAP];
	408
	409	void __init page_address_init(void)
	410	{
	411	int i;
	412
	413	INIT_LIST_HEAD(&page_address_pool);
	414	for (i = 0; i < ARRAY_SIZE(page_address_maps); i++)
	415	list_add(&page_address_maps[i].list, &page_address_pool);
	416	for (i = 0; i < ARRAY_SIZE(page_address_htable); i++) {
	417	INIT_LIST_HEAD(&page_address_htable[i].lh);
	418	spin_lock_init(&page_address_htable[i].lock);
	419	}
	420	spin_lock_init(&pool_lock);
	421	}
	422
	423	#endif /* defined(CONFIG_HIGHMEM) && !defined(WANT_PAGE_VIRTUAL) */
f4112de6 AM	424
	425	#if defined(CONFIG_DEBUG_HIGHMEM) && defined(CONFIG_TRACE_IRQFLAGS_SUPPORT)
	426
	427	void debug_kmap_atomic(enum km_type type)
	428	{
	429	static unsigned warn_count = 10;
	430
	431	if (unlikely(warn_count == 0))
	432	return;
	433
	434	if (unlikely(in_interrupt())) {
	435	if (in_irq()) {
	436	if (type != KM_IRQ0 && type != KM_IRQ1 &&
	437	type != KM_BIO_SRC_IRQ && type != KM_BIO_DST_IRQ &&
	438	type != KM_BOUNCE_READ) {
	439	WARN_ON(1);
	440	warn_count--;
	441	}
	442	} else if (!irqs_disabled()) { /* softirq */
	443	if (type != KM_IRQ0 && type != KM_IRQ1 &&
	444	type != KM_SOFTIRQ0 && type != KM_SOFTIRQ1 &&
	445	type != KM_SKB_SUNRPC_DATA &&
	446	type != KM_SKB_DATA_SOFTIRQ &&
	447	type != KM_BOUNCE_READ) {
	448	WARN_ON(1);
	449	warn_count--;
	450	}
	451	}
	452	}
	453
	454	if (type == KM_IRQ0 \|\| type == KM_IRQ1 \|\| type == KM_BOUNCE_READ \|\|
	455	type == KM_BIO_SRC_IRQ \|\| type == KM_BIO_DST_IRQ) {
	456	if (!irqs_disabled()) {
	457	WARN_ON(1);
	458	warn_count--;
	459	}
	460	} else if (type == KM_SOFTIRQ0 \|\| type == KM_SOFTIRQ1) {
	461	if (irq_count() == 0 && !irqs_disabled()) {
	462	WARN_ON(1);
	463	warn_count--;
	464	}
	465	}
	466	}
	467
	468	#endif