highmem.c revision ff3d58c22b6827039983911d3460cf0c1657f8cc 
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
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
40
41unsigned long totalhigh_pages __read_mostly;
42EXPORT_SYMBOL(totalhigh_pages);
43
44unsigned int nr_free_highpages (void)
45{
46	pg_data_t *pgdat;
47	unsigned int pages = 0;
48
49	for_each_online_pgdat(pgdat) {
50		pages += zone_page_state(&pgdat->node_zones[ZONE_HIGHMEM],
51			NR_FREE_PAGES);
52		if (zone_movable_is_highmem())
53			pages += zone_page_state(
54					&pgdat->node_zones[ZONE_MOVABLE],
55					NR_FREE_PAGES);
56	}
57
58	return pages;
59}
60
61static int pkmap_count[LAST_PKMAP];
62static unsigned int last_pkmap_nr;
63static  __cacheline_aligned_in_smp DEFINE_SPINLOCK(kmap_lock);
64
65pte_t * pkmap_page_table;
66
67static DECLARE_WAIT_QUEUE_HEAD(pkmap_map_wait);
68
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
88static void flush_all_zero_pkmaps(void)
89{
90	int i;
91	int need_flush = 0;
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 */
109		BUG_ON(pte_none(pkmap_page_table[i]));
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);
123		need_flush = 1;
124	}
125	if (need_flush)
126		flush_tlb_kernel_range(PKMAP_ADDR(0), PKMAP_ADDR(LAST_PKMAP));
127}
128
129/**
130 * kmap_flush_unused - flush all unused kmap mappings in order to remove stray mappings
131 */
132void kmap_flush_unused(void)
133{
134	lock_kmap();
135	flush_all_zero_pkmaps();
136	unlock_kmap();
137}
138
139static inline unsigned long map_new_virtual(struct page *page)
140{
141	unsigned long vaddr;
142	int count;
143
144start:
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);
166			unlock_kmap();
167			schedule();
168			remove_wait_queue(&pkmap_map_wait, &wait);
169			lock_kmap();
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
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 */
197void *kmap_high(struct page *page)
198{
199	unsigned long vaddr;
200
201	/*
202	 * For highmem pages, we can't trust "virtual" until
203	 * after we have the lock.
204	 */
205	lock_kmap();
206	vaddr = (unsigned long)page_address(page);
207	if (!vaddr)
208		vaddr = map_new_virtual(page);
209	pkmap_count[PKMAP_NR(vaddr)]++;
210	BUG_ON(pkmap_count[PKMAP_NR(vaddr)] < 2);
211	unlock_kmap();
212	return (void*) vaddr;
213}
214
215EXPORT_SYMBOL(kmap_high);
216
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.  If and only if 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 */
228void *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
243/**
244 * kunmap_high - map a highmem page into memory
245 * @page: &struct page to unmap
246 *
247 * If ARCH_NEEDS_KMAP_HIGH_GET is not defined then this may be called
248 * only from user context.
249 */
250void kunmap_high(struct page *page)
251{
252	unsigned long vaddr;
253	unsigned long nr;
254	unsigned long flags;
255	int need_wakeup;
256
257	lock_kmap_any(flags);
258	vaddr = (unsigned long)page_address(page);
259	BUG_ON(!vaddr);
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	}
283	unlock_kmap_any(flags);
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
290EXPORT_SYMBOL(kunmap_high);
291#endif
292
293#if defined(HASHED_PAGE_VIRTUAL)
294
295#define PA_HASH_ORDER	7
296
297/*
298 * Describes one page->virtual association
299 */
300struct 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 */
309static struct list_head page_address_pool;	/* freelist */
310static spinlock_t pool_lock;			/* protects page_address_pool */
311
312/*
313 * Hash table bucket
314 */
315static 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
320static struct page_address_slot *page_slot(struct page *page)
321{
322	return &page_address_htable[hash_ptr(page, PA_HASH_ORDER)];
323}
324
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 */
331void *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	}
353done:
354	spin_unlock_irqrestore(&pas->lock, flags);
355	return ret;
356}
357
358EXPORT_SYMBOL(page_address);
359
360/**
361 * set_page_address - set a page's virtual address
362 * @page: &struct page to set
363 * @virtual: virtual address to use
364 */
365void 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	}
403done:
404	return;
405}
406
407static struct page_address_map page_address_maps[LAST_PKMAP];
408
409void __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) */
424
425#ifdef CONFIG_DEBUG_HIGHMEM
426
427void debug_kmap_atomic(enum km_type type)
428{
429	static int warn_count = 10;
430
431	if (unlikely(warn_count < 0))
432		return;
433
434	if (unlikely(in_interrupt())) {
435		if (in_nmi()) {
436			if (type != KM_NMI && type != KM_NMI_PTE) {
437				WARN_ON(1);
438				warn_count--;
439			}
440		} else if (in_irq()) {
441			if (type != KM_IRQ0 && type != KM_IRQ1 &&
442			    type != KM_BIO_SRC_IRQ && type != KM_BIO_DST_IRQ &&
443			    type != KM_BOUNCE_READ && type != KM_IRQ_PTE) {
444				WARN_ON(1);
445				warn_count--;
446			}
447		} else if (!irqs_disabled()) {	/* softirq */
448			if (type != KM_IRQ0 && type != KM_IRQ1 &&
449			    type != KM_SOFTIRQ0 && type != KM_SOFTIRQ1 &&
450			    type != KM_SKB_SUNRPC_DATA &&
451			    type != KM_SKB_DATA_SOFTIRQ &&
452			    type != KM_BOUNCE_READ) {
453				WARN_ON(1);
454				warn_count--;
455			}
456		}
457	}
458
459	if (type == KM_IRQ0 || type == KM_IRQ1 || type == KM_BOUNCE_READ ||
460			type == KM_BIO_SRC_IRQ || type == KM_BIO_DST_IRQ ||
461			type == KM_IRQ_PTE || type == KM_NMI ||
462			type == KM_NMI_PTE ) {
463		if (!irqs_disabled()) {
464			WARN_ON(1);
465			warn_count--;
466		}
467	} else if (type == KM_SOFTIRQ0 || type == KM_SOFTIRQ1) {
468		if (irq_count() == 0 && !irqs_disabled()) {
469			WARN_ON(1);
470			warn_count--;
471		}
472	}
473}
474
475#endif
476