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 <linux/kgdb.h>
30#include <asm/tlbflush.h>
31
32/*
33 * Virtual_count is not a pure "count".
34 *  0 means that it is not mapped, and has not been mapped
35 *    since a TLB flush - it is usable.
36 *  1 means that there are no users, but it has been mapped
37 *    since the last TLB flush - so we can't use it.
38 *  n means that there are (n-1) current users of it.
39 */
40#ifdef CONFIG_HIGHMEM
41
42unsigned long totalhigh_pages __read_mostly;
43EXPORT_SYMBOL(totalhigh_pages);
44
45unsigned int nr_free_highpages (void)
46{
47	pg_data_t *pgdat;
48	unsigned int pages = 0;
49
50	for_each_online_pgdat(pgdat) {
51		pages += zone_page_state(&pgdat->node_zones[ZONE_HIGHMEM],
52			NR_FREE_PAGES);
53		if (zone_movable_is_highmem())
54			pages += zone_page_state(
55					&pgdat->node_zones[ZONE_MOVABLE],
56					NR_FREE_PAGES);
57	}
58
59	return pages;
60}
61
62static int pkmap_count[LAST_PKMAP];
63static unsigned int last_pkmap_nr;
64static  __cacheline_aligned_in_smp DEFINE_SPINLOCK(kmap_lock);
65
66pte_t * pkmap_page_table;
67
68static DECLARE_WAIT_QUEUE_HEAD(pkmap_map_wait);
69
70/*
71 * Most architectures have no use for kmap_high_get(), so let's abstract
72 * the disabling of IRQ out of the locking in that case to save on a
73 * potential useless overhead.
74 */
75#ifdef ARCH_NEEDS_KMAP_HIGH_GET
76#define lock_kmap()             spin_lock_irq(&kmap_lock)
77#define unlock_kmap()           spin_unlock_irq(&kmap_lock)
78#define lock_kmap_any(flags)    spin_lock_irqsave(&kmap_lock, flags)
79#define unlock_kmap_any(flags)  spin_unlock_irqrestore(&kmap_lock, flags)
80#else
81#define lock_kmap()             spin_lock(&kmap_lock)
82#define unlock_kmap()           spin_unlock(&kmap_lock)
83#define lock_kmap_any(flags)    \
84		do { spin_lock(&kmap_lock); (void)(flags); } while (0)
85#define unlock_kmap_any(flags)  \
86		do { spin_unlock(&kmap_lock); (void)(flags); } while (0)
87#endif
88
89static void flush_all_zero_pkmaps(void)
90{
91	int i;
92	int need_flush = 0;
93
94	flush_cache_kmaps();
95
96	for (i = 0; i < LAST_PKMAP; i++) {
97		struct page *page;
98
99		/*
100		 * zero means we don't have anything to do,
101		 * >1 means that it is still in use. Only
102		 * a count of 1 means that it is free but
103		 * needs to be unmapped
104		 */
105		if (pkmap_count[i] != 1)
106			continue;
107		pkmap_count[i] = 0;
108
109		/* sanity check */
110		BUG_ON(pte_none(pkmap_page_table[i]));
111
112		/*
113		 * Don't need an atomic fetch-and-clear op here;
114		 * no-one has the page mapped, and cannot get at
115		 * its virtual address (and hence PTE) without first
116		 * getting the kmap_lock (which is held here).
117		 * So no dangers, even with speculative execution.
118		 */
119		page = pte_page(pkmap_page_table[i]);
120		pte_clear(&init_mm, (unsigned long)page_address(page),
121			  &pkmap_page_table[i]);
122
123		set_page_address(page, NULL);
124		need_flush = 1;
125	}
126	if (need_flush)
127		flush_tlb_kernel_range(PKMAP_ADDR(0), PKMAP_ADDR(LAST_PKMAP));
128}
129
130/**
131 * kmap_flush_unused - flush all unused kmap mappings in order to remove stray mappings
132 */
133void kmap_flush_unused(void)
134{
135	lock_kmap();
136	flush_all_zero_pkmaps();
137	unlock_kmap();
138}
139
140static inline unsigned long map_new_virtual(struct page *page)
141{
142	unsigned long vaddr;
143	int count;
144
145start:
146	count = LAST_PKMAP;
147	/* Find an empty entry */
148	for (;;) {
149		last_pkmap_nr = (last_pkmap_nr + 1) & LAST_PKMAP_MASK;
150		if (!last_pkmap_nr) {
151			flush_all_zero_pkmaps();
152			count = LAST_PKMAP;
153		}
154		if (!pkmap_count[last_pkmap_nr])
155			break;	/* Found a usable entry */
156		if (--count)
157			continue;
158
159		/*
160		 * Sleep for somebody else to unmap their entries
161		 */
162		{
163			DECLARE_WAITQUEUE(wait, current);
164
165			__set_current_state(TASK_UNINTERRUPTIBLE);
166			add_wait_queue(&pkmap_map_wait, &wait);
167			unlock_kmap();
168			schedule();
169			remove_wait_queue(&pkmap_map_wait, &wait);
170			lock_kmap();
171
172			/* Somebody else might have mapped it while we slept */
173			if (page_address(page))
174				return (unsigned long)page_address(page);
175
176			/* Re-start */
177			goto start;
178		}
179	}
180	vaddr = PKMAP_ADDR(last_pkmap_nr);
181	set_pte_at(&init_mm, vaddr,
182		   &(pkmap_page_table[last_pkmap_nr]), mk_pte(page, kmap_prot));
183
184	pkmap_count[last_pkmap_nr] = 1;
185	set_page_address(page, (void *)vaddr);
186
187	return vaddr;
188}
189
190/**
191 * kmap_high - map a highmem page into memory
192 * @page: &struct page to map
193 *
194 * Returns the page's virtual memory address.
195 *
196 * We cannot call this from interrupts, as it may block.
197 */
198void *kmap_high(struct page *page)
199{
200	unsigned long vaddr;
201
202	/*
203	 * For highmem pages, we can't trust "virtual" until
204	 * after we have the lock.
205	 */
206	lock_kmap();
207	vaddr = (unsigned long)page_address(page);
208	if (!vaddr)
209		vaddr = map_new_virtual(page);
210	pkmap_count[PKMAP_NR(vaddr)]++;
211	BUG_ON(pkmap_count[PKMAP_NR(vaddr)] < 2);
212	unlock_kmap();
213	return (void*) vaddr;
214}
215
216EXPORT_SYMBOL(kmap_high);
217
218#ifdef ARCH_NEEDS_KMAP_HIGH_GET
219/**
220 * kmap_high_get - pin a highmem page into memory
221 * @page: &struct page to pin
222 *
223 * Returns the page's current virtual memory address, or NULL if no mapping
224 * exists.  If and only if a non null address is returned then a
225 * matching call to kunmap_high() is necessary.
226 *
227 * This can be called from any context.
228 */
229void *kmap_high_get(struct page *page)
230{
231	unsigned long vaddr, flags;
232
233	lock_kmap_any(flags);
234	vaddr = (unsigned long)page_address(page);
235	if (vaddr) {
236		BUG_ON(pkmap_count[PKMAP_NR(vaddr)] < 1);
237		pkmap_count[PKMAP_NR(vaddr)]++;
238	}
239	unlock_kmap_any(flags);
240	return (void*) vaddr;
241}
242#endif
243
244/**
245 * kunmap_high - map a highmem page into memory
246 * @page: &struct page to unmap
247 *
248 * If ARCH_NEEDS_KMAP_HIGH_GET is not defined then this may be called
249 * only from user context.
250 */
251void kunmap_high(struct page *page)
252{
253	unsigned long vaddr;
254	unsigned long nr;
255	unsigned long flags;
256	int need_wakeup;
257
258	lock_kmap_any(flags);
259	vaddr = (unsigned long)page_address(page);
260	BUG_ON(!vaddr);
261	nr = PKMAP_NR(vaddr);
262
263	/*
264	 * A count must never go down to zero
265	 * without a TLB flush!
266	 */
267	need_wakeup = 0;
268	switch (--pkmap_count[nr]) {
269	case 0:
270		BUG();
271	case 1:
272		/*
273		 * Avoid an unnecessary wake_up() function call.
274		 * The common case is pkmap_count[] == 1, but
275		 * no waiters.
276		 * The tasks queued in the wait-queue are guarded
277		 * by both the lock in the wait-queue-head and by
278		 * the kmap_lock.  As the kmap_lock is held here,
279		 * no need for the wait-queue-head's lock.  Simply
280		 * test if the queue is empty.
281		 */
282		need_wakeup = waitqueue_active(&pkmap_map_wait);
283	}
284	unlock_kmap_any(flags);
285
286	/* do wake-up, if needed, race-free outside of the spin lock */
287	if (need_wakeup)
288		wake_up(&pkmap_map_wait);
289}
290
291EXPORT_SYMBOL(kunmap_high);
292#endif
293
294#if defined(HASHED_PAGE_VIRTUAL)
295
296#define PA_HASH_ORDER	7
297
298/*
299 * Describes one page->virtual association
300 */
301struct page_address_map {
302	struct page *page;
303	void *virtual;
304	struct list_head list;
305};
306
307/*
308 * page_address_map freelist, allocated from page_address_maps.
309 */
310static struct list_head page_address_pool;	/* freelist */
311static spinlock_t pool_lock;			/* protects page_address_pool */
312
313/*
314 * Hash table bucket
315 */
316static struct page_address_slot {
317	struct list_head lh;			/* List of page_address_maps */
318	spinlock_t lock;			/* Protect this bucket's list */
319} ____cacheline_aligned_in_smp page_address_htable[1<<PA_HASH_ORDER];
320
321static struct page_address_slot *page_slot(struct page *page)
322{
323	return &page_address_htable[hash_ptr(page, PA_HASH_ORDER)];
324}
325
326/**
327 * page_address - get the mapped virtual address of a page
328 * @page: &struct page to get the virtual address of
329 *
330 * Returns the page's virtual address.
331 */
332void *page_address(struct page *page)
333{
334	unsigned long flags;
335	void *ret;
336	struct page_address_slot *pas;
337
338	if (!PageHighMem(page))
339		return lowmem_page_address(page);
340
341	pas = page_slot(page);
342	ret = NULL;
343	spin_lock_irqsave(&pas->lock, flags);
344	if (!list_empty(&pas->lh)) {
345		struct page_address_map *pam;
346
347		list_for_each_entry(pam, &pas->lh, list) {
348			if (pam->page == page) {
349				ret = pam->virtual;
350				goto done;
351			}
352		}
353	}
354done:
355	spin_unlock_irqrestore(&pas->lock, flags);
356	return ret;
357}
358
359EXPORT_SYMBOL(page_address);
360
361/**
362 * set_page_address - set a page's virtual address
363 * @page: &struct page to set
364 * @virtual: virtual address to use
365 */
366void set_page_address(struct page *page, void *virtual)
367{
368	unsigned long flags;
369	struct page_address_slot *pas;
370	struct page_address_map *pam;
371
372	BUG_ON(!PageHighMem(page));
373
374	pas = page_slot(page);
375	if (virtual) {		/* Add */
376		BUG_ON(list_empty(&page_address_pool));
377
378		spin_lock_irqsave(&pool_lock, flags);
379		pam = list_entry(page_address_pool.next,
380				struct page_address_map, list);
381		list_del(&pam->list);
382		spin_unlock_irqrestore(&pool_lock, flags);
383
384		pam->page = page;
385		pam->virtual = virtual;
386
387		spin_lock_irqsave(&pas->lock, flags);
388		list_add_tail(&pam->list, &pas->lh);
389		spin_unlock_irqrestore(&pas->lock, flags);
390	} else {		/* Remove */
391		spin_lock_irqsave(&pas->lock, flags);
392		list_for_each_entry(pam, &pas->lh, list) {
393			if (pam->page == page) {
394				list_del(&pam->list);
395				spin_unlock_irqrestore(&pas->lock, flags);
396				spin_lock_irqsave(&pool_lock, flags);
397				list_add_tail(&pam->list, &page_address_pool);
398				spin_unlock_irqrestore(&pool_lock, flags);
399				goto done;
400			}
401		}
402		spin_unlock_irqrestore(&pas->lock, flags);
403	}
404done:
405	return;
406}
407
408static struct page_address_map page_address_maps[LAST_PKMAP];
409
410void __init page_address_init(void)
411{
412	int i;
413
414	INIT_LIST_HEAD(&page_address_pool);
415	for (i = 0; i < ARRAY_SIZE(page_address_maps); i++)
416		list_add(&page_address_maps[i].list, &page_address_pool);
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	}
421	spin_lock_init(&pool_lock);
422}
423
424#endif	/* defined(CONFIG_HIGHMEM) && !defined(WANT_PAGE_VIRTUAL) */
425
426#ifdef CONFIG_DEBUG_HIGHMEM
427
428void debug_kmap_atomic(enum km_type type)
429{
430	static int warn_count = 10;
431
432	if (unlikely(warn_count < 0))
433		return;
434
435	if (unlikely(in_interrupt())) {
436		if (in_nmi()) {
437			if (type != KM_NMI && type != KM_NMI_PTE) {
438				WARN_ON(1);
439				warn_count--;
440			}
441		} else if (in_irq()) {
442			if (type != KM_IRQ0 && type != KM_IRQ1 &&
443			    type != KM_BIO_SRC_IRQ && type != KM_BIO_DST_IRQ &&
444			    type != KM_BOUNCE_READ && type != KM_IRQ_PTE) {
445				WARN_ON(1);
446				warn_count--;
447			}
448		} else if (!irqs_disabled()) {	/* softirq */
449			if (type != KM_IRQ0 && type != KM_IRQ1 &&
450			    type != KM_SOFTIRQ0 && type != KM_SOFTIRQ1 &&
451			    type != KM_SKB_SUNRPC_DATA &&
452			    type != KM_SKB_DATA_SOFTIRQ &&
453			    type != KM_BOUNCE_READ) {
454				WARN_ON(1);
455				warn_count--;
456			}
457		}
458	}
459
460	if (type == KM_IRQ0 || type == KM_IRQ1 || type == KM_BOUNCE_READ ||
461			type == KM_BIO_SRC_IRQ || type == KM_BIO_DST_IRQ ||
462			type == KM_IRQ_PTE || type == KM_NMI ||
463			type == KM_NMI_PTE ) {
464		if (!irqs_disabled()) {
465			WARN_ON(1);
466			warn_count--;
467		}
468	} else if (type == KM_SOFTIRQ0 || type == KM_SOFTIRQ1) {
469		if (irq_count() == 0 && !irqs_disabled()) {
470			WARN_ON(1);
471			warn_count--;
472		}
473	}
474#ifdef CONFIG_KGDB_KDB
475	if (unlikely(type == KM_KDB && atomic_read(&kgdb_active) == -1)) {
476		WARN_ON(1);
477		warn_count--;
478	}
479#endif /* CONFIG_KGDB_KDB */
480}
481
482#endif
483