[linux.git] / mm / highmem.c

// SPDX-License-Identifier: GPL-2.0
/*
 * 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

/*
 * Architecture with aliasing data cache may define the following family of
 * helper functions in its asm/highmem.h to control cache color of virtual
 * addresses where physical memory pages are mapped by kmap.
 */
#ifndef get_pkmap_color

/*
 * Determine color of virtual address where the page should be mapped.
 */
static inline unsigned int get_pkmap_color(struct page *page)
{
	return 0;
}
#define get_pkmap_color get_pkmap_color

/*
 * Get next index for mapping inside PKMAP region for page with given color.
 */
static inline unsigned int get_next_pkmap_nr(unsigned int color)
{
	static unsigned int last_pkmap_nr;

	last_pkmap_nr = (last_pkmap_nr + 1) & LAST_PKMAP_MASK;
	return last_pkmap_nr;
}

/*
 * Determine if page index inside PKMAP region (pkmap_nr) of given color
 * has wrapped around PKMAP region end. When this happens an attempt to
 * flush all unused PKMAP slots is made.
 */
static inline int no_more_pkmaps(unsigned int pkmap_nr, unsigned int color)
{
	return pkmap_nr == 0;
}

/*
 * Get the number of PKMAP entries of the given color. If no free slot is
 * found after checking that many entries, kmap will sleep waiting for
 * someone to call kunmap and free PKMAP slot.
 */
static inline int get_pkmap_entries_count(unsigned int color)
{
	return LAST_PKMAP;
}

/*
 * Get head of a wait queue for PKMAP entries of the given color.
 * Wait queues for different mapping colors should be independent to avoid
 * unnecessary wakeups caused by freeing of slots of other colors.
 */
static inline wait_queue_head_t *get_pkmap_wait_queue_head(unsigned int color)
{
	static DECLARE_WAIT_QUEUE_HEAD(pkmap_map_wait);

	return &pkmap_map_wait;
}
#endif

atomic_long_t _totalhigh_pages __read_mostly;
EXPORT_SYMBOL(_totalhigh_pages);

EXPORT_PER_CPU_SYMBOL(__kmap_atomic_idx);

unsigned int nr_free_highpages (void)
{
	struct zone *zone;
	unsigned int pages = 0;

	for_each_populated_zone(zone) {
		if (is_highmem(zone))
			pages += zone_page_state(zone, NR_FREE_PAGES);
	}

	return pages;
}

static int pkmap_count[LAST_PKMAP];
static  __cacheline_aligned_in_smp DEFINE_SPINLOCK(kmap_lock);

pte_t * pkmap_page_table;

/*
 * 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;
	unsigned int last_pkmap_nr;
	unsigned int color = get_pkmap_color(page);

start:
	count = get_pkmap_entries_count(color);
	/* Find an empty entry */
	for (;;) {
		last_pkmap_nr = get_next_pkmap_nr(color);
		if (no_more_pkmaps(last_pkmap_nr, color)) {
			flush_all_zero_pkmaps();
			count = get_pkmap_entries_count(color);
		}
		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);
			wait_queue_head_t *pkmap_map_wait =
				get_pkmap_wait_queue_head(color);

			__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;
	unsigned int color = get_pkmap_color(page);
	wait_queue_head_t *pkmap_map_wait;

	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.
		 */
		pkmap_map_wait = get_pkmap_wait_queue_head(color);
		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
b2441318	1	// SPDX-License-Identifier: GPL-2.0
1da177e4 LT	2	/*
	3	* High memory handling common code and variables.
	4	*
	5	* (C) 1999 Andrea Arcangeli, SuSE GmbH, [email protected]
	6	* Gerhard Wichert, Siemens AG, [email protected]
	7	*
	8	*
	9	* Redesigned the x86 32-bit VM architecture to deal with
	10	* 64-bit physical space. With current x86 CPUs this
	11	* means up to 64 Gigabytes physical RAM.
	12	*
	13	* Rewrote high memory support to move the page cache into
	14	* high memory. Implemented permanent (schedulable) kmaps
	15	* based on Linus' idea.
	16	*
	17	* Copyright (C) 1999 Ingo Molnar <[email protected]>
	18	*/
	19
	20	#include <linux/mm.h>
b95f1b31	21	#include <linux/export.h>
1da177e4 LT	22	#include <linux/swap.h>
	23	#include <linux/bio.h>
	24	#include <linux/pagemap.h>
	25	#include <linux/mempool.h>
	26	#include <linux/blkdev.h>
	27	#include <linux/init.h>
	28	#include <linux/hash.h>
	29	#include <linux/highmem.h>
eac79005	30	#include <linux/kgdb.h>
1da177e4 LT	31	#include <asm/tlbflush.h>
1da177e4 LT	32
a8e23a29 PZ	33
	34	#if defined(CONFIG_HIGHMEM) \|\| defined(CONFIG_X86_32)
	35	DEFINE_PER_CPU(int, __kmap_atomic_idx);
	36	#endif
	37
1da177e4 LT	38	/*
	39	* Virtual_count is not a pure "count".
	40	* 0 means that it is not mapped, and has not been mapped
	41	* since a TLB flush - it is usable.
	42	* 1 means that there are no users, but it has been mapped
	43	* since the last TLB flush - so we can't use it.
	44	* n means that there are (n-1) current users of it.
	45	*/
	46	#ifdef CONFIG_HIGHMEM
260b2367	47
15de36a4 MF	48	/*
	49	* Architecture with aliasing data cache may define the following family of
	50	* helper functions in its asm/highmem.h to control cache color of virtual
	51	* addresses where physical memory pages are mapped by kmap.
	52	*/
	53	#ifndef get_pkmap_color
	54
	55	/*
	56	* Determine color of virtual address where the page should be mapped.
	57	*/
	58	static inline unsigned int get_pkmap_color(struct page *page)
	59	{
	60	return 0;
	61	}
	62	#define get_pkmap_color get_pkmap_color
	63
	64	/*
	65	* Get next index for mapping inside PKMAP region for page with given color.
	66	*/
	67	static inline unsigned int get_next_pkmap_nr(unsigned int color)
	68	{
	69	static unsigned int last_pkmap_nr;
	70
	71	last_pkmap_nr = (last_pkmap_nr + 1) & LAST_PKMAP_MASK;
	72	return last_pkmap_nr;
	73	}
	74
	75	/*
	76	* Determine if page index inside PKMAP region (pkmap_nr) of given color
	77	* has wrapped around PKMAP region end. When this happens an attempt to
	78	* flush all unused PKMAP slots is made.
	79	*/
	80	static inline int no_more_pkmaps(unsigned int pkmap_nr, unsigned int color)
	81	{
	82	return pkmap_nr == 0;
	83	}
	84
	85	/*
	86	* Get the number of PKMAP entries of the given color. If no free slot is
	87	* found after checking that many entries, kmap will sleep waiting for
	88	* someone to call kunmap and free PKMAP slot.
	89	*/
	90	static inline int get_pkmap_entries_count(unsigned int color)
	91	{
	92	return LAST_PKMAP;
	93	}
	94
	95	/*
	96	* Get head of a wait queue for PKMAP entries of the given color.
	97	* Wait queues for different mapping colors should be independent to avoid
	98	* unnecessary wakeups caused by freeing of slots of other colors.
	99	*/
	100	static inline wait_queue_head_t *get_pkmap_wait_queue_head(unsigned int color)
	101	{
	102	static DECLARE_WAIT_QUEUE_HEAD(pkmap_map_wait);
	103
	104	return &pkmap_map_wait;
	105	}
	106	#endif
	107
ca79b0c2 AK	108	atomic_long_t _totalhigh_pages __read_mostly;
ca79b0c2 AK	109	EXPORT_SYMBOL(_totalhigh_pages);
3e4d3af5	110
3e4d3af5 PZ	111	EXPORT_PER_CPU_SYMBOL(__kmap_atomic_idx);
3e4d3af5 PZ	112
c1f60a5a CL	113	unsigned int nr_free_highpages (void)
c1f60a5a CL	114	{
33499bfe	115	struct zone *zone;
c1f60a5a CL	116	unsigned int pages = 0;
c1f60a5a CL	117
33499bfe JK	118	for_each_populated_zone(zone) {
	119	if (is_highmem(zone))
	120	pages += zone_page_state(zone, NR_FREE_PAGES);
2a1e274a	121	}
c1f60a5a CL	122
	123	return pages;
	124	}
	125
1da177e4	126	static int pkmap_count[LAST_PKMAP];
1da177e4 LT	127	static __cacheline_aligned_in_smp DEFINE_SPINLOCK(kmap_lock);
	128
	129	pte_t * pkmap_page_table;
	130
3297e760 NP	131	/*
	132	* Most architectures have no use for kmap_high_get(), so let's abstract
	133	* the disabling of IRQ out of the locking in that case to save on a
	134	* potential useless overhead.
	135	*/
	136	#ifdef ARCH_NEEDS_KMAP_HIGH_GET
	137	#define lock_kmap() spin_lock_irq(&kmap_lock)
	138	#define unlock_kmap() spin_unlock_irq(&kmap_lock)
	139	#define lock_kmap_any(flags) spin_lock_irqsave(&kmap_lock, flags)
	140	#define unlock_kmap_any(flags) spin_unlock_irqrestore(&kmap_lock, flags)
	141	#else
	142	#define lock_kmap() spin_lock(&kmap_lock)
	143	#define unlock_kmap() spin_unlock(&kmap_lock)
	144	#define lock_kmap_any(flags) \
	145	do { spin_lock(&kmap_lock); (void)(flags); } while (0)
	146	#define unlock_kmap_any(flags) \
	147	do { spin_unlock(&kmap_lock); (void)(flags); } while (0)
	148	#endif
	149
5a178119 MG	150	struct page kmap_to_page(void vaddr)
	151	{
	152	unsigned long addr = (unsigned long)vaddr;
	153
498c2280	154	if (addr >= PKMAP_ADDR(0) && addr < PKMAP_ADDR(LAST_PKMAP)) {
4de22c05	155	int i = PKMAP_NR(addr);
5a178119 MG	156	return pte_page(pkmap_page_table[i]);
	157	}
	158
	159	return virt_to_page(addr);
	160	}
f0263d2d	161	EXPORT_SYMBOL(kmap_to_page);
5a178119	162
1da177e4 LT	163	static void flush_all_zero_pkmaps(void)
	164	{
	165	int i;
5843d9a4	166	int need_flush = 0;
1da177e4 LT	167
	168	flush_cache_kmaps();
	169
	170	for (i = 0; i < LAST_PKMAP; i++) {
	171	struct page *page;
	172
	173	/*
	174	* zero means we don't have anything to do,
	175	* >1 means that it is still in use. Only
	176	* a count of 1 means that it is free but
	177	* needs to be unmapped
	178	*/
	179	if (pkmap_count[i] != 1)
	180	continue;
	181	pkmap_count[i] = 0;
	182
	183	/* sanity check */
75babcac	184	BUG_ON(pte_none(pkmap_page_table[i]));
1da177e4 LT	185
	186	/*
	187	* Don't need an atomic fetch-and-clear op here;
	188	* no-one has the page mapped, and cannot get at
	189	* its virtual address (and hence PTE) without first
	190	* getting the kmap_lock (which is held here).
	191	* So no dangers, even with speculative execution.
	192	*/
	193	page = pte_page(pkmap_page_table[i]);
eb2db439	194	pte_clear(&init_mm, PKMAP_ADDR(i), &pkmap_page_table[i]);
1da177e4 LT	195
1da177e4 LT	196	set_page_address(page, NULL);
5843d9a4	197	need_flush = 1;
1da177e4	198	}
5843d9a4 NP	199	if (need_flush)
5843d9a4 NP	200	flush_tlb_kernel_range(PKMAP_ADDR(0), PKMAP_ADDR(LAST_PKMAP));
1da177e4 LT	201	}
1da177e4 LT	202
77f6078a RD	203	/**
	204	* kmap_flush_unused - flush all unused kmap mappings in order to remove stray mappings
	205	*/
ce6234b5 JF	206	void kmap_flush_unused(void)
ce6234b5 JF	207	{
3297e760	208	lock_kmap();
ce6234b5	209	flush_all_zero_pkmaps();
3297e760	210	unlock_kmap();
ce6234b5 JF	211	}
ce6234b5 JF	212
1da177e4 LT	213	static inline unsigned long map_new_virtual(struct page *page)
	214	{
	215	unsigned long vaddr;
	216	int count;
15de36a4 MF	217	unsigned int last_pkmap_nr;
15de36a4 MF	218	unsigned int color = get_pkmap_color(page);
1da177e4 LT	219
1da177e4 LT	220	start:
15de36a4	221	count = get_pkmap_entries_count(color);
1da177e4 LT	222	/* Find an empty entry */
1da177e4 LT	223	for (;;) {
15de36a4 MF	224	last_pkmap_nr = get_next_pkmap_nr(color);
15de36a4 MF	225	if (no_more_pkmaps(last_pkmap_nr, color)) {
1da177e4	226	flush_all_zero_pkmaps();
15de36a4	227	count = get_pkmap_entries_count(color);
1da177e4 LT	228	}
	229	if (!pkmap_count[last_pkmap_nr])
	230	break; /* Found a usable entry */
	231	if (--count)
	232	continue;
	233
	234	/*
	235	* Sleep for somebody else to unmap their entries
	236	*/
	237	{
	238	DECLARE_WAITQUEUE(wait, current);
15de36a4 MF	239	wait_queue_head_t *pkmap_map_wait =
15de36a4 MF	240	get_pkmap_wait_queue_head(color);
1da177e4 LT	241
1da177e4 LT	242	__set_current_state(TASK_UNINTERRUPTIBLE);
15de36a4	243	add_wait_queue(pkmap_map_wait, &wait);
3297e760	244	unlock_kmap();
1da177e4	245	schedule();
15de36a4	246	remove_wait_queue(pkmap_map_wait, &wait);
3297e760	247	lock_kmap();
1da177e4 LT	248
	249	/* Somebody else might have mapped it while we slept */
	250	if (page_address(page))
	251	return (unsigned long)page_address(page);
	252
	253	/* Re-start */
	254	goto start;
	255	}
	256	}
	257	vaddr = PKMAP_ADDR(last_pkmap_nr);
	258	set_pte_at(&init_mm, vaddr,
	259	&(pkmap_page_table[last_pkmap_nr]), mk_pte(page, kmap_prot));
	260
	261	pkmap_count[last_pkmap_nr] = 1;
	262	set_page_address(page, (void *)vaddr);
	263
	264	return vaddr;
	265	}
	266
77f6078a RD	267	/**
	268	* kmap_high - map a highmem page into memory
	269	* @page: &struct page to map
	270	*
	271	* Returns the page's virtual memory address.
	272	*
	273	* We cannot call this from interrupts, as it may block.
	274	*/
920c7a5d	275	void kmap_high(struct page page)
1da177e4 LT	276	{
	277	unsigned long vaddr;
	278
	279	/*
	280	* For highmem pages, we can't trust "virtual" until
	281	* after we have the lock.
1da177e4	282	*/
3297e760	283	lock_kmap();
1da177e4 LT	284	vaddr = (unsigned long)page_address(page);
	285	if (!vaddr)
	286	vaddr = map_new_virtual(page);
	287	pkmap_count[PKMAP_NR(vaddr)]++;
75babcac	288	BUG_ON(pkmap_count[PKMAP_NR(vaddr)] < 2);
3297e760	289	unlock_kmap();
1da177e4 LT	290	return (void*) vaddr;
	291	}
	292
	293	EXPORT_SYMBOL(kmap_high);
	294
3297e760 NP	295	#ifdef ARCH_NEEDS_KMAP_HIGH_GET
	296	/**
	297	* kmap_high_get - pin a highmem page into memory
	298	* @page: &struct page to pin
	299	*
	300	* Returns the page's current virtual memory address, or NULL if no mapping
5e39df56	301	* exists. If and only if a non null address is returned then a
3297e760 NP	302	* matching call to kunmap_high() is necessary.
	303	*
	304	* This can be called from any context.
	305	*/
	306	void kmap_high_get(struct page page)
	307	{
	308	unsigned long vaddr, flags;
	309
	310	lock_kmap_any(flags);
	311	vaddr = (unsigned long)page_address(page);
	312	if (vaddr) {
	313	BUG_ON(pkmap_count[PKMAP_NR(vaddr)] < 1);
	314	pkmap_count[PKMAP_NR(vaddr)]++;
	315	}
	316	unlock_kmap_any(flags);
	317	return (void*) vaddr;
	318	}
	319	#endif
	320
77f6078a	321	/**
4e9dc5df	322	* kunmap_high - unmap a highmem page into memory
77f6078a	323	* @page: &struct page to unmap
3297e760 NP	324	*
	325	* If ARCH_NEEDS_KMAP_HIGH_GET is not defined then this may be called
	326	* only from user context.
77f6078a	327	*/
920c7a5d	328	void kunmap_high(struct page *page)
1da177e4 LT	329	{
	330	unsigned long vaddr;
	331	unsigned long nr;
3297e760	332	unsigned long flags;
1da177e4	333	int need_wakeup;
15de36a4 MF	334	unsigned int color = get_pkmap_color(page);
15de36a4 MF	335	wait_queue_head_t *pkmap_map_wait;
1da177e4	336
3297e760	337	lock_kmap_any(flags);
1da177e4	338	vaddr = (unsigned long)page_address(page);
75babcac	339	BUG_ON(!vaddr);
1da177e4 LT	340	nr = PKMAP_NR(vaddr);
	341
	342	/*
	343	* A count must never go down to zero
	344	* without a TLB flush!
	345	*/
	346	need_wakeup = 0;
	347	switch (--pkmap_count[nr]) {
	348	case 0:
	349	BUG();
	350	case 1:
	351	/*
	352	* Avoid an unnecessary wake_up() function call.
	353	* The common case is pkmap_count[] == 1, but
	354	* no waiters.
	355	* The tasks queued in the wait-queue are guarded
	356	* by both the lock in the wait-queue-head and by
	357	* the kmap_lock. As the kmap_lock is held here,
	358	* no need for the wait-queue-head's lock. Simply
	359	* test if the queue is empty.
	360	*/
15de36a4 MF	361	pkmap_map_wait = get_pkmap_wait_queue_head(color);
15de36a4 MF	362	need_wakeup = waitqueue_active(pkmap_map_wait);
1da177e4	363	}
3297e760	364	unlock_kmap_any(flags);
1da177e4 LT	365
	366	/* do wake-up, if needed, race-free outside of the spin lock */
	367	if (need_wakeup)
15de36a4	368	wake_up(pkmap_map_wait);
1da177e4 LT	369	}
	370
	371	EXPORT_SYMBOL(kunmap_high);
1da177e4 LT	372	#endif
1da177e4 LT	373
1da177e4 LT	374	#if defined(HASHED_PAGE_VIRTUAL)
	375
	376	#define PA_HASH_ORDER 7
	377
	378	/*
	379	* Describes one page->virtual association
	380	*/
	381	struct page_address_map {
	382	struct page *page;
	383	void *virtual;
	384	struct list_head list;
	385	};
	386
a354e2c8	387	static struct page_address_map page_address_maps[LAST_PKMAP];
1da177e4 LT	388
	389	/*
	390	* Hash table bucket
	391	*/
	392	static struct page_address_slot {
	393	struct list_head lh; /* List of page_address_maps */
	394	spinlock_t lock; /* Protect this bucket's list */
	395	} ____cacheline_aligned_in_smp page_address_htable[1<<PA_HASH_ORDER];
	396
f9918794	397	static struct page_address_slot page_slot(const struct page page)
1da177e4 LT	398	{
	399	return &page_address_htable[hash_ptr(page, PA_HASH_ORDER)];
	400	}
	401
77f6078a RD	402	/**
	403	* page_address - get the mapped virtual address of a page
	404	* @page: &struct page to get the virtual address of
	405	*
	406	* Returns the page's virtual address.
	407	*/
f9918794	408	void page_address(const struct page page)
1da177e4 LT	409	{
	410	unsigned long flags;
	411	void *ret;
	412	struct page_address_slot *pas;
	413
	414	if (!PageHighMem(page))
	415	return lowmem_page_address(page);
	416
	417	pas = page_slot(page);
	418	ret = NULL;
	419	spin_lock_irqsave(&pas->lock, flags);
	420	if (!list_empty(&pas->lh)) {
	421	struct page_address_map *pam;
	422
	423	list_for_each_entry(pam, &pas->lh, list) {
	424	if (pam->page == page) {
	425	ret = pam->virtual;
	426	goto done;
	427	}
	428	}
	429	}
	430	done:
	431	spin_unlock_irqrestore(&pas->lock, flags);
	432	return ret;
	433	}
	434
	435	EXPORT_SYMBOL(page_address);
	436
77f6078a RD	437	/**
	438	* set_page_address - set a page's virtual address
	439	* @page: &struct page to set
	440	* @virtual: virtual address to use
	441	*/
1da177e4 LT	442	void set_page_address(struct page page, void virtual)
	443	{
	444	unsigned long flags;
	445	struct page_address_slot *pas;
	446	struct page_address_map *pam;
	447
	448	BUG_ON(!PageHighMem(page));
	449
	450	pas = page_slot(page);
	451	if (virtual) { /* Add */
a354e2c8	452	pam = &page_address_maps[PKMAP_NR((unsigned long)virtual)];
1da177e4 LT	453	pam->page = page;
	454	pam->virtual = virtual;
	455
	456	spin_lock_irqsave(&pas->lock, flags);
	457	list_add_tail(&pam->list, &pas->lh);
	458	spin_unlock_irqrestore(&pas->lock, flags);
	459	} else { /* Remove */
	460	spin_lock_irqsave(&pas->lock, flags);
	461	list_for_each_entry(pam, &pas->lh, list) {
	462	if (pam->page == page) {
	463	list_del(&pam->list);
	464	spin_unlock_irqrestore(&pas->lock, flags);
1da177e4 LT	465	goto done;
	466	}
	467	}
	468	spin_unlock_irqrestore(&pas->lock, flags);
	469	}
	470	done:
	471	return;
	472	}
	473
1da177e4 LT	474	void __init page_address_init(void)
	475	{
	476	int i;
	477
1da177e4 LT	478	for (i = 0; i < ARRAY_SIZE(page_address_htable); i++) {
	479	INIT_LIST_HEAD(&page_address_htable[i].lh);
	480	spin_lock_init(&page_address_htable[i].lock);
	481	}
1da177e4 LT	482	}
	483
	484	#endif /* defined(CONFIG_HIGHMEM) && !defined(WANT_PAGE_VIRTUAL) */