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1// SPDX-License-Identifier: GPL-2.0
2/*
3 * High memory handling common code and variables.
4 *
5 * (C) 1999 Andrea Arcangeli, SuSE GmbH, andrea@suse.de
6 * Gerhard Wichert, Siemens AG, Gerhard.Wichert@pdb.siemens.de
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 <mingo@redhat.com>
18 */
19
20#include <linux/mm.h>
21#include <linux/export.h>
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>
30#include <linux/kgdb.h>
31#include <asm/tlbflush.h>
32
33
34#if defined(CONFIG_HIGHMEM) || defined(CONFIG_X86_32)
35DEFINE_PER_CPU(int, __kmap_atomic_idx);
36#endif
37
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
47
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 */
58static 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 */
67static 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 */
80static 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 */
90static 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 */
100static 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
108unsigned long totalhigh_pages __read_mostly;
109EXPORT_SYMBOL(totalhigh_pages);
110
111
112EXPORT_PER_CPU_SYMBOL(__kmap_atomic_idx);
113
114unsigned int nr_free_highpages (void)
115{
116 struct zone *zone;
117 unsigned int pages = 0;
118
119 for_each_populated_zone(zone) {
120 if (is_highmem(zone))
121 pages += zone_page_state(zone, NR_FREE_PAGES);
122 }
123
124 return pages;
125}
126
127static int pkmap_count[LAST_PKMAP];
128static __cacheline_aligned_in_smp DEFINE_SPINLOCK(kmap_lock);
129
130pte_t * pkmap_page_table;
131
132/*
133 * Most architectures have no use for kmap_high_get(), so let's abstract
134 * the disabling of IRQ out of the locking in that case to save on a
135 * potential useless overhead.
136 */
137#ifdef ARCH_NEEDS_KMAP_HIGH_GET
138#define lock_kmap() spin_lock_irq(&kmap_lock)
139#define unlock_kmap() spin_unlock_irq(&kmap_lock)
140#define lock_kmap_any(flags) spin_lock_irqsave(&kmap_lock, flags)
141#define unlock_kmap_any(flags) spin_unlock_irqrestore(&kmap_lock, flags)
142#else
143#define lock_kmap() spin_lock(&kmap_lock)
144#define unlock_kmap() spin_unlock(&kmap_lock)
145#define lock_kmap_any(flags) \
146 do { spin_lock(&kmap_lock); (void)(flags); } while (0)
147#define unlock_kmap_any(flags) \
148 do { spin_unlock(&kmap_lock); (void)(flags); } while (0)
149#endif
150
151struct page *kmap_to_page(void *vaddr)
152{
153 unsigned long addr = (unsigned long)vaddr;
154
155 if (addr >= PKMAP_ADDR(0) && addr < PKMAP_ADDR(LAST_PKMAP)) {
156 int i = PKMAP_NR(addr);
157 return pte_page(pkmap_page_table[i]);
158 }
159
160 return virt_to_page(addr);
161}
162EXPORT_SYMBOL(kmap_to_page);
163
164static void flush_all_zero_pkmaps(void)
165{
166 int i;
167 int need_flush = 0;
168
169 flush_cache_kmaps();
170
171 for (i = 0; i < LAST_PKMAP; i++) {
172 struct page *page;
173
174 /*
175 * zero means we don't have anything to do,
176 * >1 means that it is still in use. Only
177 * a count of 1 means that it is free but
178 * needs to be unmapped
179 */
180 if (pkmap_count[i] != 1)
181 continue;
182 pkmap_count[i] = 0;
183
184 /* sanity check */
185 BUG_ON(pte_none(pkmap_page_table[i]));
186
187 /*
188 * Don't need an atomic fetch-and-clear op here;
189 * no-one has the page mapped, and cannot get at
190 * its virtual address (and hence PTE) without first
191 * getting the kmap_lock (which is held here).
192 * So no dangers, even with speculative execution.
193 */
194 page = pte_page(pkmap_page_table[i]);
195 pte_clear(&init_mm, PKMAP_ADDR(i), &pkmap_page_table[i]);
196
197 set_page_address(page, NULL);
198 need_flush = 1;
199 }
200 if (need_flush)
201 flush_tlb_kernel_range(PKMAP_ADDR(0), PKMAP_ADDR(LAST_PKMAP));
202}
203
204/**
205 * kmap_flush_unused - flush all unused kmap mappings in order to remove stray mappings
206 */
207void kmap_flush_unused(void)
208{
209 lock_kmap();
210 flush_all_zero_pkmaps();
211 unlock_kmap();
212}
213
214static inline unsigned long map_new_virtual(struct page *page)
215{
216 unsigned long vaddr;
217 int count;
218 unsigned int last_pkmap_nr;
219 unsigned int color = get_pkmap_color(page);
220
221start:
222 count = get_pkmap_entries_count(color);
223 /* Find an empty entry */
224 for (;;) {
225 last_pkmap_nr = get_next_pkmap_nr(color);
226 if (no_more_pkmaps(last_pkmap_nr, color)) {
227 flush_all_zero_pkmaps();
228 count = get_pkmap_entries_count(color);
229 }
230 if (!pkmap_count[last_pkmap_nr])
231 break; /* Found a usable entry */
232 if (--count)
233 continue;
234
235 /*
236 * Sleep for somebody else to unmap their entries
237 */
238 {
239 DECLARE_WAITQUEUE(wait, current);
240 wait_queue_head_t *pkmap_map_wait =
241 get_pkmap_wait_queue_head(color);
242
243 __set_current_state(TASK_UNINTERRUPTIBLE);
244 add_wait_queue(pkmap_map_wait, &wait);
245 unlock_kmap();
246 schedule();
247 remove_wait_queue(pkmap_map_wait, &wait);
248 lock_kmap();
249
250 /* Somebody else might have mapped it while we slept */
251 if (page_address(page))
252 return (unsigned long)page_address(page);
253
254 /* Re-start */
255 goto start;
256 }
257 }
258 vaddr = PKMAP_ADDR(last_pkmap_nr);
259 set_pte_at(&init_mm, vaddr,
260 &(pkmap_page_table[last_pkmap_nr]), mk_pte(page, kmap_prot));
261
262 pkmap_count[last_pkmap_nr] = 1;
263 set_page_address(page, (void *)vaddr);
264
265 return vaddr;
266}
267
268/**
269 * kmap_high - map a highmem page into memory
270 * @page: &struct page to map
271 *
272 * Returns the page's virtual memory address.
273 *
274 * We cannot call this from interrupts, as it may block.
275 */
276void *kmap_high(struct page *page)
277{
278 unsigned long vaddr;
279
280 /*
281 * For highmem pages, we can't trust "virtual" until
282 * after we have the lock.
283 */
284 lock_kmap();
285 vaddr = (unsigned long)page_address(page);
286 if (!vaddr)
287 vaddr = map_new_virtual(page);
288 pkmap_count[PKMAP_NR(vaddr)]++;
289 BUG_ON(pkmap_count[PKMAP_NR(vaddr)] < 2);
290 unlock_kmap();
291 return (void*) vaddr;
292}
293
294EXPORT_SYMBOL(kmap_high);
295
296#ifdef ARCH_NEEDS_KMAP_HIGH_GET
297/**
298 * kmap_high_get - pin a highmem page into memory
299 * @page: &struct page to pin
300 *
301 * Returns the page's current virtual memory address, or NULL if no mapping
302 * exists. If and only if a non null address is returned then a
303 * matching call to kunmap_high() is necessary.
304 *
305 * This can be called from any context.
306 */
307void *kmap_high_get(struct page *page)
308{
309 unsigned long vaddr, flags;
310
311 lock_kmap_any(flags);
312 vaddr = (unsigned long)page_address(page);
313 if (vaddr) {
314 BUG_ON(pkmap_count[PKMAP_NR(vaddr)] < 1);
315 pkmap_count[PKMAP_NR(vaddr)]++;
316 }
317 unlock_kmap_any(flags);
318 return (void*) vaddr;
319}
320#endif
321
322/**
323 * kunmap_high - unmap a highmem page into memory
324 * @page: &struct page to unmap
325 *
326 * If ARCH_NEEDS_KMAP_HIGH_GET is not defined then this may be called
327 * only from user context.
328 */
329void kunmap_high(struct page *page)
330{
331 unsigned long vaddr;
332 unsigned long nr;
333 unsigned long flags;
334 int need_wakeup;
335 unsigned int color = get_pkmap_color(page);
336 wait_queue_head_t *pkmap_map_wait;
337
338 lock_kmap_any(flags);
339 vaddr = (unsigned long)page_address(page);
340 BUG_ON(!vaddr);
341 nr = PKMAP_NR(vaddr);
342
343 /*
344 * A count must never go down to zero
345 * without a TLB flush!
346 */
347 need_wakeup = 0;
348 switch (--pkmap_count[nr]) {
349 case 0:
350 BUG();
351 case 1:
352 /*
353 * Avoid an unnecessary wake_up() function call.
354 * The common case is pkmap_count[] == 1, but
355 * no waiters.
356 * The tasks queued in the wait-queue are guarded
357 * by both the lock in the wait-queue-head and by
358 * the kmap_lock. As the kmap_lock is held here,
359 * no need for the wait-queue-head's lock. Simply
360 * test if the queue is empty.
361 */
362 pkmap_map_wait = get_pkmap_wait_queue_head(color);
363 need_wakeup = waitqueue_active(pkmap_map_wait);
364 }
365 unlock_kmap_any(flags);
366
367 /* do wake-up, if needed, race-free outside of the spin lock */
368 if (need_wakeup)
369 wake_up(pkmap_map_wait);
370}
371
372EXPORT_SYMBOL(kunmap_high);
373#endif
374
375#if defined(HASHED_PAGE_VIRTUAL)
376
377#define PA_HASH_ORDER 7
378
379/*
380 * Describes one page->virtual association
381 */
382struct page_address_map {
383 struct page *page;
384 void *virtual;
385 struct list_head list;
386};
387
388static struct page_address_map page_address_maps[LAST_PKMAP];
389
390/*
391 * Hash table bucket
392 */
393static struct page_address_slot {
394 struct list_head lh; /* List of page_address_maps */
395 spinlock_t lock; /* Protect this bucket's list */
396} ____cacheline_aligned_in_smp page_address_htable[1<<PA_HASH_ORDER];
397
398static struct page_address_slot *page_slot(const struct page *page)
399{
400 return &page_address_htable[hash_ptr(page, PA_HASH_ORDER)];
401}
402
403/**
404 * page_address - get the mapped virtual address of a page
405 * @page: &struct page to get the virtual address of
406 *
407 * Returns the page's virtual address.
408 */
409void *page_address(const struct page *page)
410{
411 unsigned long flags;
412 void *ret;
413 struct page_address_slot *pas;
414
415 if (!PageHighMem(page))
416 return lowmem_page_address(page);
417
418 pas = page_slot(page);
419 ret = NULL;
420 spin_lock_irqsave(&pas->lock, flags);
421 if (!list_empty(&pas->lh)) {
422 struct page_address_map *pam;
423
424 list_for_each_entry(pam, &pas->lh, list) {
425 if (pam->page == page) {
426 ret = pam->virtual;
427 goto done;
428 }
429 }
430 }
431done:
432 spin_unlock_irqrestore(&pas->lock, flags);
433 return ret;
434}
435
436EXPORT_SYMBOL(page_address);
437
438/**
439 * set_page_address - set a page's virtual address
440 * @page: &struct page to set
441 * @virtual: virtual address to use
442 */
443void set_page_address(struct page *page, void *virtual)
444{
445 unsigned long flags;
446 struct page_address_slot *pas;
447 struct page_address_map *pam;
448
449 BUG_ON(!PageHighMem(page));
450
451 pas = page_slot(page);
452 if (virtual) { /* Add */
453 pam = &page_address_maps[PKMAP_NR((unsigned long)virtual)];
454 pam->page = page;
455 pam->virtual = virtual;
456
457 spin_lock_irqsave(&pas->lock, flags);
458 list_add_tail(&pam->list, &pas->lh);
459 spin_unlock_irqrestore(&pas->lock, flags);
460 } else { /* Remove */
461 spin_lock_irqsave(&pas->lock, flags);
462 list_for_each_entry(pam, &pas->lh, list) {
463 if (pam->page == page) {
464 list_del(&pam->list);
465 spin_unlock_irqrestore(&pas->lock, flags);
466 goto done;
467 }
468 }
469 spin_unlock_irqrestore(&pas->lock, flags);
470 }
471done:
472 return;
473}
474
475void __init page_address_init(void)
476{
477 int i;
478
479 for (i = 0; i < ARRAY_SIZE(page_address_htable); i++) {
480 INIT_LIST_HEAD(&page_address_htable[i].lh);
481 spin_lock_init(&page_address_htable[i].lock);
482 }
483}
484
485#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/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
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
97struct page *kmap_to_page(void *vaddr)
98{
99 unsigned long addr = (unsigned long)vaddr;
100
101 if (addr >= PKMAP_ADDR(0) && addr < PKMAP_ADDR(LAST_PKMAP)) {
102 int i = PKMAP_NR(addr);
103 return pte_page(pkmap_page_table[i]);
104 }
105
106 return virt_to_page(addr);
107}
108EXPORT_SYMBOL(kmap_to_page);
109
110static void flush_all_zero_pkmaps(void)
111{
112 int i;
113 int need_flush = 0;
114
115 flush_cache_kmaps();
116
117 for (i = 0; i < LAST_PKMAP; i++) {
118 struct page *page;
119
120 /*
121 * zero means we don't have anything to do,
122 * >1 means that it is still in use. Only
123 * a count of 1 means that it is free but
124 * needs to be unmapped
125 */
126 if (pkmap_count[i] != 1)
127 continue;
128 pkmap_count[i] = 0;
129
130 /* sanity check */
131 BUG_ON(pte_none(pkmap_page_table[i]));
132
133 /*
134 * Don't need an atomic fetch-and-clear op here;
135 * no-one has the page mapped, and cannot get at
136 * its virtual address (and hence PTE) without first
137 * getting the kmap_lock (which is held here).
138 * So no dangers, even with speculative execution.
139 */
140 page = pte_page(pkmap_page_table[i]);
141 pte_clear(&init_mm, PKMAP_ADDR(i), &pkmap_page_table[i]);
142
143 set_page_address(page, NULL);
144 need_flush = 1;
145 }
146 if (need_flush)
147 flush_tlb_kernel_range(PKMAP_ADDR(0), PKMAP_ADDR(LAST_PKMAP));
148}
149
150/**
151 * kmap_flush_unused - flush all unused kmap mappings in order to remove stray mappings
152 */
153void kmap_flush_unused(void)
154{
155 lock_kmap();
156 flush_all_zero_pkmaps();
157 unlock_kmap();
158}
159
160static inline unsigned long map_new_virtual(struct page *page)
161{
162 unsigned long vaddr;
163 int count;
164
165start:
166 count = LAST_PKMAP;
167 /* Find an empty entry */
168 for (;;) {
169 last_pkmap_nr = (last_pkmap_nr + 1) & LAST_PKMAP_MASK;
170 if (!last_pkmap_nr) {
171 flush_all_zero_pkmaps();
172 count = LAST_PKMAP;
173 }
174 if (!pkmap_count[last_pkmap_nr])
175 break; /* Found a usable entry */
176 if (--count)
177 continue;
178
179 /*
180 * Sleep for somebody else to unmap their entries
181 */
182 {
183 DECLARE_WAITQUEUE(wait, current);
184
185 __set_current_state(TASK_UNINTERRUPTIBLE);
186 add_wait_queue(&pkmap_map_wait, &wait);
187 unlock_kmap();
188 schedule();
189 remove_wait_queue(&pkmap_map_wait, &wait);
190 lock_kmap();
191
192 /* Somebody else might have mapped it while we slept */
193 if (page_address(page))
194 return (unsigned long)page_address(page);
195
196 /* Re-start */
197 goto start;
198 }
199 }
200 vaddr = PKMAP_ADDR(last_pkmap_nr);
201 set_pte_at(&init_mm, vaddr,
202 &(pkmap_page_table[last_pkmap_nr]), mk_pte(page, kmap_prot));
203
204 pkmap_count[last_pkmap_nr] = 1;
205 set_page_address(page, (void *)vaddr);
206
207 return vaddr;
208}
209
210/**
211 * kmap_high - map a highmem page into memory
212 * @page: &struct page to map
213 *
214 * Returns the page's virtual memory address.
215 *
216 * We cannot call this from interrupts, as it may block.
217 */
218void *kmap_high(struct page *page)
219{
220 unsigned long vaddr;
221
222 /*
223 * For highmem pages, we can't trust "virtual" until
224 * after we have the lock.
225 */
226 lock_kmap();
227 vaddr = (unsigned long)page_address(page);
228 if (!vaddr)
229 vaddr = map_new_virtual(page);
230 pkmap_count[PKMAP_NR(vaddr)]++;
231 BUG_ON(pkmap_count[PKMAP_NR(vaddr)] < 2);
232 unlock_kmap();
233 return (void*) vaddr;
234}
235
236EXPORT_SYMBOL(kmap_high);
237
238#ifdef ARCH_NEEDS_KMAP_HIGH_GET
239/**
240 * kmap_high_get - pin a highmem page into memory
241 * @page: &struct page to pin
242 *
243 * Returns the page's current virtual memory address, or NULL if no mapping
244 * exists. If and only if a non null address is returned then a
245 * matching call to kunmap_high() is necessary.
246 *
247 * This can be called from any context.
248 */
249void *kmap_high_get(struct page *page)
250{
251 unsigned long vaddr, flags;
252
253 lock_kmap_any(flags);
254 vaddr = (unsigned long)page_address(page);
255 if (vaddr) {
256 BUG_ON(pkmap_count[PKMAP_NR(vaddr)] < 1);
257 pkmap_count[PKMAP_NR(vaddr)]++;
258 }
259 unlock_kmap_any(flags);
260 return (void*) vaddr;
261}
262#endif
263
264/**
265 * kunmap_high - unmap a highmem page into memory
266 * @page: &struct page to unmap
267 *
268 * If ARCH_NEEDS_KMAP_HIGH_GET is not defined then this may be called
269 * only from user context.
270 */
271void kunmap_high(struct page *page)
272{
273 unsigned long vaddr;
274 unsigned long nr;
275 unsigned long flags;
276 int need_wakeup;
277
278 lock_kmap_any(flags);
279 vaddr = (unsigned long)page_address(page);
280 BUG_ON(!vaddr);
281 nr = PKMAP_NR(vaddr);
282
283 /*
284 * A count must never go down to zero
285 * without a TLB flush!
286 */
287 need_wakeup = 0;
288 switch (--pkmap_count[nr]) {
289 case 0:
290 BUG();
291 case 1:
292 /*
293 * Avoid an unnecessary wake_up() function call.
294 * The common case is pkmap_count[] == 1, but
295 * no waiters.
296 * The tasks queued in the wait-queue are guarded
297 * by both the lock in the wait-queue-head and by
298 * the kmap_lock. As the kmap_lock is held here,
299 * no need for the wait-queue-head's lock. Simply
300 * test if the queue is empty.
301 */
302 need_wakeup = waitqueue_active(&pkmap_map_wait);
303 }
304 unlock_kmap_any(flags);
305
306 /* do wake-up, if needed, race-free outside of the spin lock */
307 if (need_wakeup)
308 wake_up(&pkmap_map_wait);
309}
310
311EXPORT_SYMBOL(kunmap_high);
312#endif
313
314#if defined(HASHED_PAGE_VIRTUAL)
315
316#define PA_HASH_ORDER 7
317
318/*
319 * Describes one page->virtual association
320 */
321struct page_address_map {
322 struct page *page;
323 void *virtual;
324 struct list_head list;
325};
326
327static struct page_address_map page_address_maps[LAST_PKMAP];
328
329/*
330 * Hash table bucket
331 */
332static struct page_address_slot {
333 struct list_head lh; /* List of page_address_maps */
334 spinlock_t lock; /* Protect this bucket's list */
335} ____cacheline_aligned_in_smp page_address_htable[1<<PA_HASH_ORDER];
336
337static struct page_address_slot *page_slot(const struct page *page)
338{
339 return &page_address_htable[hash_ptr(page, PA_HASH_ORDER)];
340}
341
342/**
343 * page_address - get the mapped virtual address of a page
344 * @page: &struct page to get the virtual address of
345 *
346 * Returns the page's virtual address.
347 */
348void *page_address(const struct page *page)
349{
350 unsigned long flags;
351 void *ret;
352 struct page_address_slot *pas;
353
354 if (!PageHighMem(page))
355 return lowmem_page_address(page);
356
357 pas = page_slot(page);
358 ret = NULL;
359 spin_lock_irqsave(&pas->lock, flags);
360 if (!list_empty(&pas->lh)) {
361 struct page_address_map *pam;
362
363 list_for_each_entry(pam, &pas->lh, list) {
364 if (pam->page == page) {
365 ret = pam->virtual;
366 goto done;
367 }
368 }
369 }
370done:
371 spin_unlock_irqrestore(&pas->lock, flags);
372 return ret;
373}
374
375EXPORT_SYMBOL(page_address);
376
377/**
378 * set_page_address - set a page's virtual address
379 * @page: &struct page to set
380 * @virtual: virtual address to use
381 */
382void set_page_address(struct page *page, void *virtual)
383{
384 unsigned long flags;
385 struct page_address_slot *pas;
386 struct page_address_map *pam;
387
388 BUG_ON(!PageHighMem(page));
389
390 pas = page_slot(page);
391 if (virtual) { /* Add */
392 pam = &page_address_maps[PKMAP_NR((unsigned long)virtual)];
393 pam->page = page;
394 pam->virtual = virtual;
395
396 spin_lock_irqsave(&pas->lock, flags);
397 list_add_tail(&pam->list, &pas->lh);
398 spin_unlock_irqrestore(&pas->lock, flags);
399 } else { /* Remove */
400 spin_lock_irqsave(&pas->lock, flags);
401 list_for_each_entry(pam, &pas->lh, list) {
402 if (pam->page == page) {
403 list_del(&pam->list);
404 spin_unlock_irqrestore(&pas->lock, flags);
405 goto done;
406 }
407 }
408 spin_unlock_irqrestore(&pas->lock, flags);
409 }
410done:
411 return;
412}
413
414void __init page_address_init(void)
415{
416 int i;
417
418 for (i = 0; i < ARRAY_SIZE(page_address_htable); i++) {
419 INIT_LIST_HEAD(&page_address_htable[i].lh);
420 spin_lock_init(&page_address_htable[i].lock);
421 }
422}
423
424#endif /* defined(CONFIG_HIGHMEM) && !defined(WANT_PAGE_VIRTUAL) */