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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/export.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#if defined(CONFIG_HIGHMEM) || defined(CONFIG_X86_32)
34DEFINE_PER_CPU(int, __kmap_atomic_idx);
35#endif
36
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
46
47/*
48 * Architecture with aliasing data cache may define the following family of
49 * helper functions in its asm/highmem.h to control cache color of virtual
50 * addresses where physical memory pages are mapped by kmap.
51 */
52#ifndef get_pkmap_color
53
54/*
55 * Determine color of virtual address where the page should be mapped.
56 */
57static inline unsigned int get_pkmap_color(struct page *page)
58{
59 return 0;
60}
61#define get_pkmap_color get_pkmap_color
62
63/*
64 * Get next index for mapping inside PKMAP region for page with given color.
65 */
66static inline unsigned int get_next_pkmap_nr(unsigned int color)
67{
68 static unsigned int last_pkmap_nr;
69
70 last_pkmap_nr = (last_pkmap_nr + 1) & LAST_PKMAP_MASK;
71 return last_pkmap_nr;
72}
73
74/*
75 * Determine if page index inside PKMAP region (pkmap_nr) of given color
76 * has wrapped around PKMAP region end. When this happens an attempt to
77 * flush all unused PKMAP slots is made.
78 */
79static inline int no_more_pkmaps(unsigned int pkmap_nr, unsigned int color)
80{
81 return pkmap_nr == 0;
82}
83
84/*
85 * Get the number of PKMAP entries of the given color. If no free slot is
86 * found after checking that many entries, kmap will sleep waiting for
87 * someone to call kunmap and free PKMAP slot.
88 */
89static inline int get_pkmap_entries_count(unsigned int color)
90{
91 return LAST_PKMAP;
92}
93
94/*
95 * Get head of a wait queue for PKMAP entries of the given color.
96 * Wait queues for different mapping colors should be independent to avoid
97 * unnecessary wakeups caused by freeing of slots of other colors.
98 */
99static inline wait_queue_head_t *get_pkmap_wait_queue_head(unsigned int color)
100{
101 static DECLARE_WAIT_QUEUE_HEAD(pkmap_map_wait);
102
103 return &pkmap_map_wait;
104}
105#endif
106
107unsigned long totalhigh_pages __read_mostly;
108EXPORT_SYMBOL(totalhigh_pages);
109
110
111EXPORT_PER_CPU_SYMBOL(__kmap_atomic_idx);
112
113unsigned int nr_free_highpages (void)
114{
115 pg_data_t *pgdat;
116 unsigned int pages = 0;
117
118 for_each_online_pgdat(pgdat) {
119 pages += zone_page_state(&pgdat->node_zones[ZONE_HIGHMEM],
120 NR_FREE_PAGES);
121 if (zone_movable_is_highmem())
122 pages += zone_page_state(
123 &pgdat->node_zones[ZONE_MOVABLE],
124 NR_FREE_PAGES);
125 }
126
127 return pages;
128}
129
130static int pkmap_count[LAST_PKMAP];
131static __cacheline_aligned_in_smp DEFINE_SPINLOCK(kmap_lock);
132
133pte_t * pkmap_page_table;
134
135/*
136 * Most architectures have no use for kmap_high_get(), so let's abstract
137 * the disabling of IRQ out of the locking in that case to save on a
138 * potential useless overhead.
139 */
140#ifdef ARCH_NEEDS_KMAP_HIGH_GET
141#define lock_kmap() spin_lock_irq(&kmap_lock)
142#define unlock_kmap() spin_unlock_irq(&kmap_lock)
143#define lock_kmap_any(flags) spin_lock_irqsave(&kmap_lock, flags)
144#define unlock_kmap_any(flags) spin_unlock_irqrestore(&kmap_lock, flags)
145#else
146#define lock_kmap() spin_lock(&kmap_lock)
147#define unlock_kmap() spin_unlock(&kmap_lock)
148#define lock_kmap_any(flags) \
149 do { spin_lock(&kmap_lock); (void)(flags); } while (0)
150#define unlock_kmap_any(flags) \
151 do { spin_unlock(&kmap_lock); (void)(flags); } while (0)
152#endif
153
154struct page *kmap_to_page(void *vaddr)
155{
156 unsigned long addr = (unsigned long)vaddr;
157
158 if (addr >= PKMAP_ADDR(0) && addr < PKMAP_ADDR(LAST_PKMAP)) {
159 int i = PKMAP_NR(addr);
160 return pte_page(pkmap_page_table[i]);
161 }
162
163 return virt_to_page(addr);
164}
165EXPORT_SYMBOL(kmap_to_page);
166
167static void flush_all_zero_pkmaps(void)
168{
169 int i;
170 int need_flush = 0;
171
172 flush_cache_kmaps();
173
174 for (i = 0; i < LAST_PKMAP; i++) {
175 struct page *page;
176
177 /*
178 * zero means we don't have anything to do,
179 * >1 means that it is still in use. Only
180 * a count of 1 means that it is free but
181 * needs to be unmapped
182 */
183 if (pkmap_count[i] != 1)
184 continue;
185 pkmap_count[i] = 0;
186
187 /* sanity check */
188 BUG_ON(pte_none(pkmap_page_table[i]));
189
190 /*
191 * Don't need an atomic fetch-and-clear op here;
192 * no-one has the page mapped, and cannot get at
193 * its virtual address (and hence PTE) without first
194 * getting the kmap_lock (which is held here).
195 * So no dangers, even with speculative execution.
196 */
197 page = pte_page(pkmap_page_table[i]);
198 pte_clear(&init_mm, PKMAP_ADDR(i), &pkmap_page_table[i]);
199
200 set_page_address(page, NULL);
201 need_flush = 1;
202 }
203 if (need_flush)
204 flush_tlb_kernel_range(PKMAP_ADDR(0), PKMAP_ADDR(LAST_PKMAP));
205}
206
207/**
208 * kmap_flush_unused - flush all unused kmap mappings in order to remove stray mappings
209 */
210void kmap_flush_unused(void)
211{
212 lock_kmap();
213 flush_all_zero_pkmaps();
214 unlock_kmap();
215}
216
217static inline unsigned long map_new_virtual(struct page *page)
218{
219 unsigned long vaddr;
220 int count;
221 unsigned int last_pkmap_nr;
222 unsigned int color = get_pkmap_color(page);
223
224start:
225 count = get_pkmap_entries_count(color);
226 /* Find an empty entry */
227 for (;;) {
228 last_pkmap_nr = get_next_pkmap_nr(color);
229 if (no_more_pkmaps(last_pkmap_nr, color)) {
230 flush_all_zero_pkmaps();
231 count = get_pkmap_entries_count(color);
232 }
233 if (!pkmap_count[last_pkmap_nr])
234 break; /* Found a usable entry */
235 if (--count)
236 continue;
237
238 /*
239 * Sleep for somebody else to unmap their entries
240 */
241 {
242 DECLARE_WAITQUEUE(wait, current);
243 wait_queue_head_t *pkmap_map_wait =
244 get_pkmap_wait_queue_head(color);
245
246 __set_current_state(TASK_UNINTERRUPTIBLE);
247 add_wait_queue(pkmap_map_wait, &wait);
248 unlock_kmap();
249 schedule();
250 remove_wait_queue(pkmap_map_wait, &wait);
251 lock_kmap();
252
253 /* Somebody else might have mapped it while we slept */
254 if (page_address(page))
255 return (unsigned long)page_address(page);
256
257 /* Re-start */
258 goto start;
259 }
260 }
261 vaddr = PKMAP_ADDR(last_pkmap_nr);
262 set_pte_at(&init_mm, vaddr,
263 &(pkmap_page_table[last_pkmap_nr]), mk_pte(page, kmap_prot));
264
265 pkmap_count[last_pkmap_nr] = 1;
266 set_page_address(page, (void *)vaddr);
267
268 return vaddr;
269}
270
271/**
272 * kmap_high - map a highmem page into memory
273 * @page: &struct page to map
274 *
275 * Returns the page's virtual memory address.
276 *
277 * We cannot call this from interrupts, as it may block.
278 */
279void *kmap_high(struct page *page)
280{
281 unsigned long vaddr;
282
283 /*
284 * For highmem pages, we can't trust "virtual" until
285 * after we have the lock.
286 */
287 lock_kmap();
288 vaddr = (unsigned long)page_address(page);
289 if (!vaddr)
290 vaddr = map_new_virtual(page);
291 pkmap_count[PKMAP_NR(vaddr)]++;
292 BUG_ON(pkmap_count[PKMAP_NR(vaddr)] < 2);
293 unlock_kmap();
294 return (void*) vaddr;
295}
296
297EXPORT_SYMBOL(kmap_high);
298
299#ifdef ARCH_NEEDS_KMAP_HIGH_GET
300/**
301 * kmap_high_get - pin a highmem page into memory
302 * @page: &struct page to pin
303 *
304 * Returns the page's current virtual memory address, or NULL if no mapping
305 * exists. If and only if a non null address is returned then a
306 * matching call to kunmap_high() is necessary.
307 *
308 * This can be called from any context.
309 */
310void *kmap_high_get(struct page *page)
311{
312 unsigned long vaddr, flags;
313
314 lock_kmap_any(flags);
315 vaddr = (unsigned long)page_address(page);
316 if (vaddr) {
317 BUG_ON(pkmap_count[PKMAP_NR(vaddr)] < 1);
318 pkmap_count[PKMAP_NR(vaddr)]++;
319 }
320 unlock_kmap_any(flags);
321 return (void*) vaddr;
322}
323#endif
324
325/**
326 * kunmap_high - unmap a highmem page into memory
327 * @page: &struct page to unmap
328 *
329 * If ARCH_NEEDS_KMAP_HIGH_GET is not defined then this may be called
330 * only from user context.
331 */
332void kunmap_high(struct page *page)
333{
334 unsigned long vaddr;
335 unsigned long nr;
336 unsigned long flags;
337 int need_wakeup;
338 unsigned int color = get_pkmap_color(page);
339 wait_queue_head_t *pkmap_map_wait;
340
341 lock_kmap_any(flags);
342 vaddr = (unsigned long)page_address(page);
343 BUG_ON(!vaddr);
344 nr = PKMAP_NR(vaddr);
345
346 /*
347 * A count must never go down to zero
348 * without a TLB flush!
349 */
350 need_wakeup = 0;
351 switch (--pkmap_count[nr]) {
352 case 0:
353 BUG();
354 case 1:
355 /*
356 * Avoid an unnecessary wake_up() function call.
357 * The common case is pkmap_count[] == 1, but
358 * no waiters.
359 * The tasks queued in the wait-queue are guarded
360 * by both the lock in the wait-queue-head and by
361 * the kmap_lock. As the kmap_lock is held here,
362 * no need for the wait-queue-head's lock. Simply
363 * test if the queue is empty.
364 */
365 pkmap_map_wait = get_pkmap_wait_queue_head(color);
366 need_wakeup = waitqueue_active(pkmap_map_wait);
367 }
368 unlock_kmap_any(flags);
369
370 /* do wake-up, if needed, race-free outside of the spin lock */
371 if (need_wakeup)
372 wake_up(pkmap_map_wait);
373}
374
375EXPORT_SYMBOL(kunmap_high);
376#endif
377
378#if defined(HASHED_PAGE_VIRTUAL)
379
380#define PA_HASH_ORDER 7
381
382/*
383 * Describes one page->virtual association
384 */
385struct page_address_map {
386 struct page *page;
387 void *virtual;
388 struct list_head list;
389};
390
391static struct page_address_map page_address_maps[LAST_PKMAP];
392
393/*
394 * Hash table bucket
395 */
396static struct page_address_slot {
397 struct list_head lh; /* List of page_address_maps */
398 spinlock_t lock; /* Protect this bucket's list */
399} ____cacheline_aligned_in_smp page_address_htable[1<<PA_HASH_ORDER];
400
401static struct page_address_slot *page_slot(const struct page *page)
402{
403 return &page_address_htable[hash_ptr(page, PA_HASH_ORDER)];
404}
405
406/**
407 * page_address - get the mapped virtual address of a page
408 * @page: &struct page to get the virtual address of
409 *
410 * Returns the page's virtual address.
411 */
412void *page_address(const struct page *page)
413{
414 unsigned long flags;
415 void *ret;
416 struct page_address_slot *pas;
417
418 if (!PageHighMem(page))
419 return lowmem_page_address(page);
420
421 pas = page_slot(page);
422 ret = NULL;
423 spin_lock_irqsave(&pas->lock, flags);
424 if (!list_empty(&pas->lh)) {
425 struct page_address_map *pam;
426
427 list_for_each_entry(pam, &pas->lh, list) {
428 if (pam->page == page) {
429 ret = pam->virtual;
430 goto done;
431 }
432 }
433 }
434done:
435 spin_unlock_irqrestore(&pas->lock, flags);
436 return ret;
437}
438
439EXPORT_SYMBOL(page_address);
440
441/**
442 * set_page_address - set a page's virtual address
443 * @page: &struct page to set
444 * @virtual: virtual address to use
445 */
446void set_page_address(struct page *page, void *virtual)
447{
448 unsigned long flags;
449 struct page_address_slot *pas;
450 struct page_address_map *pam;
451
452 BUG_ON(!PageHighMem(page));
453
454 pas = page_slot(page);
455 if (virtual) { /* Add */
456 pam = &page_address_maps[PKMAP_NR((unsigned long)virtual)];
457 pam->page = page;
458 pam->virtual = virtual;
459
460 spin_lock_irqsave(&pas->lock, flags);
461 list_add_tail(&pam->list, &pas->lh);
462 spin_unlock_irqrestore(&pas->lock, flags);
463 } else { /* Remove */
464 spin_lock_irqsave(&pas->lock, flags);
465 list_for_each_entry(pam, &pas->lh, list) {
466 if (pam->page == page) {
467 list_del(&pam->list);
468 spin_unlock_irqrestore(&pas->lock, flags);
469 goto done;
470 }
471 }
472 spin_unlock_irqrestore(&pas->lock, flags);
473 }
474done:
475 return;
476}
477
478void __init page_address_init(void)
479{
480 int i;
481
482 for (i = 0; i < ARRAY_SIZE(page_address_htable); i++) {
483 INIT_LIST_HEAD(&page_address_htable[i].lh);
484 spin_lock_init(&page_address_htable[i].lock);
485 }
486}
487
488#endif /* defined(CONFIG_HIGHMEM) && !defined(WANT_PAGE_VIRTUAL) */
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#if defined(CONFIG_HIGHMEM) || defined(CONFIG_X86_32)
34DEFINE_PER_CPU(int, __kmap_atomic_idx);
35#endif
36
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
46
47unsigned long totalhigh_pages __read_mostly;
48EXPORT_SYMBOL(totalhigh_pages);
49
50
51EXPORT_PER_CPU_SYMBOL(__kmap_atomic_idx);
52
53unsigned int nr_free_highpages (void)
54{
55 pg_data_t *pgdat;
56 unsigned int pages = 0;
57
58 for_each_online_pgdat(pgdat) {
59 pages += zone_page_state(&pgdat->node_zones[ZONE_HIGHMEM],
60 NR_FREE_PAGES);
61 if (zone_movable_is_highmem())
62 pages += zone_page_state(
63 &pgdat->node_zones[ZONE_MOVABLE],
64 NR_FREE_PAGES);
65 }
66
67 return pages;
68}
69
70static int pkmap_count[LAST_PKMAP];
71static unsigned int last_pkmap_nr;
72static __cacheline_aligned_in_smp DEFINE_SPINLOCK(kmap_lock);
73
74pte_t * pkmap_page_table;
75
76static DECLARE_WAIT_QUEUE_HEAD(pkmap_map_wait);
77
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
97static void flush_all_zero_pkmaps(void)
98{
99 int i;
100 int need_flush = 0;
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 */
118 BUG_ON(pte_none(pkmap_page_table[i]));
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);
132 need_flush = 1;
133 }
134 if (need_flush)
135 flush_tlb_kernel_range(PKMAP_ADDR(0), PKMAP_ADDR(LAST_PKMAP));
136}
137
138/**
139 * kmap_flush_unused - flush all unused kmap mappings in order to remove stray mappings
140 */
141void kmap_flush_unused(void)
142{
143 lock_kmap();
144 flush_all_zero_pkmaps();
145 unlock_kmap();
146}
147
148static inline unsigned long map_new_virtual(struct page *page)
149{
150 unsigned long vaddr;
151 int count;
152
153start:
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);
175 unlock_kmap();
176 schedule();
177 remove_wait_queue(&pkmap_map_wait, &wait);
178 lock_kmap();
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
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 */
206void *kmap_high(struct page *page)
207{
208 unsigned long vaddr;
209
210 /*
211 * For highmem pages, we can't trust "virtual" until
212 * after we have the lock.
213 */
214 lock_kmap();
215 vaddr = (unsigned long)page_address(page);
216 if (!vaddr)
217 vaddr = map_new_virtual(page);
218 pkmap_count[PKMAP_NR(vaddr)]++;
219 BUG_ON(pkmap_count[PKMAP_NR(vaddr)] < 2);
220 unlock_kmap();
221 return (void*) vaddr;
222}
223
224EXPORT_SYMBOL(kmap_high);
225
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
232 * exists. If and only if a non null address is returned then a
233 * matching call to kunmap_high() is necessary.
234 *
235 * This can be called from any context.
236 */
237void *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
252/**
253 * kunmap_high - map a highmem page into memory
254 * @page: &struct page to unmap
255 *
256 * If ARCH_NEEDS_KMAP_HIGH_GET is not defined then this may be called
257 * only from user context.
258 */
259void kunmap_high(struct page *page)
260{
261 unsigned long vaddr;
262 unsigned long nr;
263 unsigned long flags;
264 int need_wakeup;
265
266 lock_kmap_any(flags);
267 vaddr = (unsigned long)page_address(page);
268 BUG_ON(!vaddr);
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 }
292 unlock_kmap_any(flags);
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
299EXPORT_SYMBOL(kunmap_high);
300#endif
301
302#if defined(HASHED_PAGE_VIRTUAL)
303
304#define PA_HASH_ORDER 7
305
306/*
307 * Describes one page->virtual association
308 */
309struct 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 */
318static struct list_head page_address_pool; /* freelist */
319static spinlock_t pool_lock; /* protects page_address_pool */
320
321/*
322 * Hash table bucket
323 */
324static 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
329static struct page_address_slot *page_slot(const struct page *page)
330{
331 return &page_address_htable[hash_ptr(page, PA_HASH_ORDER)];
332}
333
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 */
340void *page_address(const struct page *page)
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 }
362done:
363 spin_unlock_irqrestore(&pas->lock, flags);
364 return ret;
365}
366
367EXPORT_SYMBOL(page_address);
368
369/**
370 * set_page_address - set a page's virtual address
371 * @page: &struct page to set
372 * @virtual: virtual address to use
373 */
374void 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 }
412done:
413 return;
414}
415
416static struct page_address_map page_address_maps[LAST_PKMAP];
417
418void __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) */