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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) | |
34 | DEFINE_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 | */ | |
57 | static 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 | */ | |
66 | static 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 | */ | |
79 | static 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 | */ | |
89 | static 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 | */ | |
99 | static 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 | ||
107 | unsigned long totalhigh_pages __read_mostly; | |
108 | EXPORT_SYMBOL(totalhigh_pages); | |
109 | ||
110 | ||
111 | EXPORT_PER_CPU_SYMBOL(__kmap_atomic_idx); | |
112 | ||
113 | unsigned int nr_free_highpages (void) | |
114 | { | |
115 | struct zone *zone; | |
116 | unsigned int pages = 0; | |
117 | ||
118 | for_each_populated_zone(zone) { | |
119 | if (is_highmem(zone)) | |
120 | pages += zone_page_state(zone, NR_FREE_PAGES); | |
121 | } | |
122 | ||
123 | return pages; | |
124 | } | |
125 | ||
126 | static int pkmap_count[LAST_PKMAP]; | |
127 | static __cacheline_aligned_in_smp DEFINE_SPINLOCK(kmap_lock); | |
128 | ||
129 | pte_t * pkmap_page_table; | |
130 | ||
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 | ||
150 | struct page *kmap_to_page(void *vaddr) | |
151 | { | |
152 | unsigned long addr = (unsigned long)vaddr; | |
153 | ||
154 | if (addr >= PKMAP_ADDR(0) && addr < PKMAP_ADDR(LAST_PKMAP)) { | |
155 | int i = PKMAP_NR(addr); | |
156 | return pte_page(pkmap_page_table[i]); | |
157 | } | |
158 | ||
159 | return virt_to_page(addr); | |
160 | } | |
161 | EXPORT_SYMBOL(kmap_to_page); | |
162 | ||
163 | static void flush_all_zero_pkmaps(void) | |
164 | { | |
165 | int i; | |
166 | int need_flush = 0; | |
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 */ | |
184 | BUG_ON(pte_none(pkmap_page_table[i])); | |
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]); | |
194 | pte_clear(&init_mm, PKMAP_ADDR(i), &pkmap_page_table[i]); | |
195 | ||
196 | set_page_address(page, NULL); | |
197 | need_flush = 1; | |
198 | } | |
199 | if (need_flush) | |
200 | flush_tlb_kernel_range(PKMAP_ADDR(0), PKMAP_ADDR(LAST_PKMAP)); | |
201 | } | |
202 | ||
203 | /** | |
204 | * kmap_flush_unused - flush all unused kmap mappings in order to remove stray mappings | |
205 | */ | |
206 | void kmap_flush_unused(void) | |
207 | { | |
208 | lock_kmap(); | |
209 | flush_all_zero_pkmaps(); | |
210 | unlock_kmap(); | |
211 | } | |
212 | ||
213 | static inline unsigned long map_new_virtual(struct page *page) | |
214 | { | |
215 | unsigned long vaddr; | |
216 | int count; | |
217 | unsigned int last_pkmap_nr; | |
218 | unsigned int color = get_pkmap_color(page); | |
219 | ||
220 | start: | |
221 | count = get_pkmap_entries_count(color); | |
222 | /* Find an empty entry */ | |
223 | for (;;) { | |
224 | last_pkmap_nr = get_next_pkmap_nr(color); | |
225 | if (no_more_pkmaps(last_pkmap_nr, color)) { | |
226 | flush_all_zero_pkmaps(); | |
227 | count = get_pkmap_entries_count(color); | |
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); | |
239 | wait_queue_head_t *pkmap_map_wait = | |
240 | get_pkmap_wait_queue_head(color); | |
241 | ||
242 | __set_current_state(TASK_UNINTERRUPTIBLE); | |
243 | add_wait_queue(pkmap_map_wait, &wait); | |
244 | unlock_kmap(); | |
245 | schedule(); | |
246 | remove_wait_queue(pkmap_map_wait, &wait); | |
247 | lock_kmap(); | |
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 | ||
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 | */ | |
275 | void *kmap_high(struct page *page) | |
276 | { | |
277 | unsigned long vaddr; | |
278 | ||
279 | /* | |
280 | * For highmem pages, we can't trust "virtual" until | |
281 | * after we have the lock. | |
282 | */ | |
283 | lock_kmap(); | |
284 | vaddr = (unsigned long)page_address(page); | |
285 | if (!vaddr) | |
286 | vaddr = map_new_virtual(page); | |
287 | pkmap_count[PKMAP_NR(vaddr)]++; | |
288 | BUG_ON(pkmap_count[PKMAP_NR(vaddr)] < 2); | |
289 | unlock_kmap(); | |
290 | return (void*) vaddr; | |
291 | } | |
292 | ||
293 | EXPORT_SYMBOL(kmap_high); | |
294 | ||
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 | |
301 | * exists. If and only if a non null address is returned then a | |
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 | ||
321 | /** | |
322 | * kunmap_high - unmap a highmem page into memory | |
323 | * @page: &struct page to unmap | |
324 | * | |
325 | * If ARCH_NEEDS_KMAP_HIGH_GET is not defined then this may be called | |
326 | * only from user context. | |
327 | */ | |
328 | void kunmap_high(struct page *page) | |
329 | { | |
330 | unsigned long vaddr; | |
331 | unsigned long nr; | |
332 | unsigned long flags; | |
333 | int need_wakeup; | |
334 | unsigned int color = get_pkmap_color(page); | |
335 | wait_queue_head_t *pkmap_map_wait; | |
336 | ||
337 | lock_kmap_any(flags); | |
338 | vaddr = (unsigned long)page_address(page); | |
339 | BUG_ON(!vaddr); | |
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 | */ | |
361 | pkmap_map_wait = get_pkmap_wait_queue_head(color); | |
362 | need_wakeup = waitqueue_active(pkmap_map_wait); | |
363 | } | |
364 | unlock_kmap_any(flags); | |
365 | ||
366 | /* do wake-up, if needed, race-free outside of the spin lock */ | |
367 | if (need_wakeup) | |
368 | wake_up(pkmap_map_wait); | |
369 | } | |
370 | ||
371 | EXPORT_SYMBOL(kunmap_high); | |
372 | #endif | |
373 | ||
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 | ||
387 | static struct page_address_map page_address_maps[LAST_PKMAP]; | |
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 | ||
397 | static struct page_address_slot *page_slot(const struct page *page) | |
398 | { | |
399 | return &page_address_htable[hash_ptr(page, PA_HASH_ORDER)]; | |
400 | } | |
401 | ||
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 | */ | |
408 | void *page_address(const struct page *page) | |
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 | ||
437 | /** | |
438 | * set_page_address - set a page's virtual address | |
439 | * @page: &struct page to set | |
440 | * @virtual: virtual address to use | |
441 | */ | |
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 */ | |
452 | pam = &page_address_maps[PKMAP_NR((unsigned long)virtual)]; | |
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); | |
465 | goto done; | |
466 | } | |
467 | } | |
468 | spin_unlock_irqrestore(&pas->lock, flags); | |
469 | } | |
470 | done: | |
471 | return; | |
472 | } | |
473 | ||
474 | void __init page_address_init(void) | |
475 | { | |
476 | int i; | |
477 | ||
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 | } | |
482 | } | |
483 | ||
484 | #endif /* defined(CONFIG_HIGHMEM) && !defined(WANT_PAGE_VIRTUAL) */ |