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)
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
nr_free_highpages(void)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
flush_all_zero_pkmaps(void)97 static 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 */
kmap_flush_unused(void)141 void kmap_flush_unused(void)
142 {
143 lock_kmap();
144 flush_all_zero_pkmaps();
145 unlock_kmap();
146 }
147
map_new_virtual(struct page * page)148 static inline unsigned long map_new_virtual(struct page *page)
149 {
150 unsigned long vaddr;
151 int count;
152
153 start:
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 */
kmap_high(struct page * page)206 void *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
224 EXPORT_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 */
kmap_high_get(struct page * page)237 void *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 */
kunmap_high(struct page * page)259 void 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
299 EXPORT_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 */
309 struct 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 */
318 static struct list_head page_address_pool; /* freelist */
319 static spinlock_t pool_lock; /* protects page_address_pool */
320
321 /*
322 * Hash table bucket
323 */
324 static 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
page_slot(struct page * page)329 static struct page_address_slot *page_slot(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 */
page_address(struct page * page)340 void *page_address(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 }
362 done:
363 spin_unlock_irqrestore(&pas->lock, flags);
364 return ret;
365 }
366
367 EXPORT_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 */
set_page_address(struct page * page,void * virtual)374 void 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 }
412 done:
413 return;
414 }
415
416 static struct page_address_map page_address_maps[LAST_PKMAP];
417
page_address_init(void)418 void __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) */
433