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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 | unsigned long totalhigh_pages __read_mostly; | |
48 | EXPORT_SYMBOL(totalhigh_pages); | |
49 | ||
50 | ||
51 | EXPORT_PER_CPU_SYMBOL(__kmap_atomic_idx); | |
52 | ||
53 | unsigned 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 | ||
70 | static int pkmap_count[LAST_PKMAP]; | |
71 | static unsigned int last_pkmap_nr; | |
72 | static __cacheline_aligned_in_smp DEFINE_SPINLOCK(kmap_lock); | |
73 | ||
74 | pte_t * pkmap_page_table; | |
75 | ||
76 | static 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 | ||
97 | struct 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 | } | |
108 | ||
109 | static void flush_all_zero_pkmaps(void) | |
110 | { | |
111 | int i; | |
112 | int need_flush = 0; | |
113 | ||
114 | flush_cache_kmaps(); | |
115 | ||
116 | for (i = 0; i < LAST_PKMAP; i++) { | |
117 | struct page *page; | |
118 | ||
119 | /* | |
120 | * zero means we don't have anything to do, | |
121 | * >1 means that it is still in use. Only | |
122 | * a count of 1 means that it is free but | |
123 | * needs to be unmapped | |
124 | */ | |
125 | if (pkmap_count[i] != 1) | |
126 | continue; | |
127 | pkmap_count[i] = 0; | |
128 | ||
129 | /* sanity check */ | |
130 | BUG_ON(pte_none(pkmap_page_table[i])); | |
131 | ||
132 | /* | |
133 | * Don't need an atomic fetch-and-clear op here; | |
134 | * no-one has the page mapped, and cannot get at | |
135 | * its virtual address (and hence PTE) without first | |
136 | * getting the kmap_lock (which is held here). | |
137 | * So no dangers, even with speculative execution. | |
138 | */ | |
139 | page = pte_page(pkmap_page_table[i]); | |
140 | pte_clear(&init_mm, (unsigned long)page_address(page), | |
141 | &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 | */ | |
153 | void kmap_flush_unused(void) | |
154 | { | |
155 | lock_kmap(); | |
156 | flush_all_zero_pkmaps(); | |
157 | unlock_kmap(); | |
158 | } | |
159 | ||
160 | static inline unsigned long map_new_virtual(struct page *page) | |
161 | { | |
162 | unsigned long vaddr; | |
163 | int count; | |
164 | ||
165 | start: | |
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 | */ | |
218 | void *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 | ||
236 | EXPORT_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 | */ | |
249 | void *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 | */ | |
271 | void 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 | ||
311 | EXPORT_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 | */ | |
321 | struct page_address_map { | |
322 | struct page *page; | |
323 | void *virtual; | |
324 | struct list_head list; | |
325 | }; | |
326 | ||
327 | static struct page_address_map page_address_maps[LAST_PKMAP]; | |
328 | ||
329 | /* | |
330 | * Hash table bucket | |
331 | */ | |
332 | static 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 | ||
337 | static 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 | */ | |
348 | void *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 | } | |
370 | done: | |
371 | spin_unlock_irqrestore(&pas->lock, flags); | |
372 | return ret; | |
373 | } | |
374 | ||
375 | EXPORT_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 | */ | |
382 | void 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 | } | |
410 | done: | |
411 | return; | |
412 | } | |
413 | ||
414 | void __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) */ |