blob: 50b4ca6787f08e75037c81c853bfb5d22b1cbd36
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) */ |
485 |