1 /*
2 * linux/mm/swap.c
3 *
4 * Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds
5 */
6
7 /*
8 * This file contains the default values for the opereation of the
9 * Linux VM subsystem. Fine-tuning documentation can be found in
10 * Documentation/sysctl/vm.txt.
11 * Started 18.12.91
12 * Swap aging added 23.2.95, Stephen Tweedie.
13 * Buffermem limits added 12.3.98, Rik van Riel.
14 */
15
16 #include <linux/mm.h>
17 #include <linux/sched.h>
18 #include <linux/kernel_stat.h>
19 #include <linux/swap.h>
20 #include <linux/mman.h>
21 #include <linux/pagemap.h>
22 #include <linux/pagevec.h>
23 #include <linux/init.h>
24 #include <linux/module.h>
25 #include <linux/mm_inline.h>
26 #include <linux/buffer_head.h> /* for try_to_release_page() */
27 #include <linux/module.h>
28 #include <linux/percpu_counter.h>
29 #include <linux/percpu.h>
30 #include <linux/cpu.h>
31 #include <linux/notifier.h>
32 #include <linux/init.h>
33
34 /* How many pages do we try to swap or page in/out together? */
35 int page_cluster;
36
37 static void put_compound_page(struct page *page)
38 {
39 page = (struct page *)page_private(page);
40 if (put_page_testzero(page)) {
41 void (*dtor)(struct page *page);
42
43 dtor = (void (*)(struct page *))page[1].lru.next;
44 (*dtor)(page);
45 }
46 }
47
48 void put_page(struct page *page)
49 {
50 if (unlikely(PageCompound(page)))
51 put_compound_page(page);
52 else if (put_page_testzero(page))
53 __page_cache_release(page);
54 }
55 EXPORT_SYMBOL(put_page);
56
57 /*
58 * Writeback is about to end against a page which has been marked for immediate
59 * reclaim. If it still appears to be reclaimable, move it to the tail of the
60 * inactive list. The page still has PageWriteback set, which will pin it.
61 *
62 * We don't expect many pages to come through here, so don't bother batching
63 * things up.
64 *
65 * To avoid placing the page at the tail of the LRU while PG_writeback is still
66 * set, this function will clear PG_writeback before performing the page
67 * motion. Do that inside the lru lock because once PG_writeback is cleared
68 * we may not touch the page.
69 *
70 * Returns zero if it cleared PG_writeback.
71 */
72 int rotate_reclaimable_page(struct page *page)
73 {
74 struct zone *zone;
75 unsigned long flags;
76
77 if (PageLocked(page))
78 return 1;
79 if (PageDirty(page))
80 return 1;
81 if (PageActive(page))
82 return 1;
83 if (!PageLRU(page))
84 return 1;
85
86 zone = page_zone(page);
87 spin_lock_irqsave(&zone->lru_lock, flags);
88 if (PageLRU(page) && !PageActive(page)) {
89 list_del(&page->lru);
90 list_add_tail(&page->lru, &zone->inactive_list);
91 inc_page_state(pgrotated);
92 }
93 if (!test_clear_page_writeback(page))
94 BUG();
95 spin_unlock_irqrestore(&zone->lru_lock, flags);
96 return 0;
97 }
98
99 /*
100 * FIXME: speed this up?
101 */
102 void fastcall activate_page(struct page *page)
103 {
104 struct zone *zone = page_zone(page);
105
106 spin_lock_irq(&zone->lru_lock);
107 if (PageLRU(page) && !PageActive(page)) {
108 del_page_from_inactive_list(zone, page);
109 SetPageActive(page);
110 add_page_to_active_list(zone, page);
111 inc_page_state(pgactivate);
112 }
113 spin_unlock_irq(&zone->lru_lock);
114 }
115
116 /*
117 * Mark a page as having seen activity.
118 *
119 * inactive,unreferenced -> inactive,referenced
120 * inactive,referenced -> active,unreferenced
121 * active,unreferenced -> active,referenced
122 */
123 void fastcall mark_page_accessed(struct page *page)
124 {
125 if (!PageActive(page) && PageReferenced(page) && PageLRU(page)) {
126 activate_page(page);
127 ClearPageReferenced(page);
128 } else if (!PageReferenced(page)) {
129 SetPageReferenced(page);
130 }
131 }
132
133 EXPORT_SYMBOL(mark_page_accessed);
134
135 /**
136 * lru_cache_add: add a page to the page lists
137 * @page: the page to add
138 */
139 static DEFINE_PER_CPU(struct pagevec, lru_add_pvecs) = { 0, };
140 static DEFINE_PER_CPU(struct pagevec, lru_add_active_pvecs) = { 0, };
141
142 void fastcall lru_cache_add(struct page *page)
143 {
144 struct pagevec *pvec = &get_cpu_var(lru_add_pvecs);
145
146 page_cache_get(page);
147 if (!pagevec_add(pvec, page))
148 __pagevec_lru_add(pvec);
149 put_cpu_var(lru_add_pvecs);
150 }
151
152 void fastcall lru_cache_add_active(struct page *page)
153 {
154 struct pagevec *pvec = &get_cpu_var(lru_add_active_pvecs);
155
156 page_cache_get(page);
157 if (!pagevec_add(pvec, page))
158 __pagevec_lru_add_active(pvec);
159 put_cpu_var(lru_add_active_pvecs);
160 }
161
162 static void __lru_add_drain(int cpu)
163 {
164 struct pagevec *pvec = &per_cpu(lru_add_pvecs, cpu);
165
166 /* CPU is dead, so no locking needed. */
167 if (pagevec_count(pvec))
168 __pagevec_lru_add(pvec);
169 pvec = &per_cpu(lru_add_active_pvecs, cpu);
170 if (pagevec_count(pvec))
171 __pagevec_lru_add_active(pvec);
172 }
173
174 void lru_add_drain(void)
175 {
176 __lru_add_drain(get_cpu());
177 put_cpu();
178 }
179
180 #ifdef CONFIG_NUMA
181 static void lru_add_drain_per_cpu(void *dummy)
182 {
183 lru_add_drain();
184 }
185
186 /*
187 * Returns 0 for success
188 */
189 int lru_add_drain_all(void)
190 {
191 return schedule_on_each_cpu(lru_add_drain_per_cpu, NULL);
192 }
193
194 #else
195
196 /*
197 * Returns 0 for success
198 */
199 int lru_add_drain_all(void)
200 {
201 lru_add_drain();
202 return 0;
203 }
204 #endif
205
206 /*
207 * This path almost never happens for VM activity - pages are normally
208 * freed via pagevecs. But it gets used by networking.
209 */
210 void fastcall __page_cache_release(struct page *page)
211 {
212 if (PageLRU(page)) {
213 unsigned long flags;
214 struct zone *zone = page_zone(page);
215
216 spin_lock_irqsave(&zone->lru_lock, flags);
217 BUG_ON(!PageLRU(page));
218 __ClearPageLRU(page);
219 del_page_from_lru(zone, page);
220 spin_unlock_irqrestore(&zone->lru_lock, flags);
221 }
222 free_hot_page(page);
223 }
224 EXPORT_SYMBOL(__page_cache_release);
225
226 /*
227 * Batched page_cache_release(). Decrement the reference count on all the
228 * passed pages. If it fell to zero then remove the page from the LRU and
229 * free it.
230 *
231 * Avoid taking zone->lru_lock if possible, but if it is taken, retain it
232 * for the remainder of the operation.
233 *
234 * The locking in this function is against shrink_cache(): we recheck the
235 * page count inside the lock to see whether shrink_cache grabbed the page
236 * via the LRU. If it did, give up: shrink_cache will free it.
237 */
238 void release_pages(struct page **pages, int nr, int cold)
239 {
240 int i;
241 struct pagevec pages_to_free;
242 struct zone *zone = NULL;
243
244 pagevec_init(&pages_to_free, cold);
245 for (i = 0; i < nr; i++) {
246 struct page *page = pages[i];
247
248 if (unlikely(PageCompound(page))) {
249 if (zone) {
250 spin_unlock_irq(&zone->lru_lock);
251 zone = NULL;
252 }
253 put_compound_page(page);
254 continue;
255 }
256
257 if (!put_page_testzero(page))
258 continue;
259
260 if (PageLRU(page)) {
261 struct zone *pagezone = page_zone(page);
262 if (pagezone != zone) {
263 if (zone)
264 spin_unlock_irq(&zone->lru_lock);
265 zone = pagezone;
266 spin_lock_irq(&zone->lru_lock);
267 }
268 BUG_ON(!PageLRU(page));
269 __ClearPageLRU(page);
270 del_page_from_lru(zone, page);
271 }
272
273 if (!pagevec_add(&pages_to_free, page)) {
274 if (zone) {
275 spin_unlock_irq(&zone->lru_lock);
276 zone = NULL;
277 }
278 __pagevec_free(&pages_to_free);
279 pagevec_reinit(&pages_to_free);
280 }
281 }
282 if (zone)
283 spin_unlock_irq(&zone->lru_lock);
284
285 pagevec_free(&pages_to_free);
286 }
287
288 /*
289 * The pages which we're about to release may be in the deferred lru-addition
290 * queues. That would prevent them from really being freed right now. That's
291 * OK from a correctness point of view but is inefficient - those pages may be
292 * cache-warm and we want to give them back to the page allocator ASAP.
293 *
294 * So __pagevec_release() will drain those queues here. __pagevec_lru_add()
295 * and __pagevec_lru_add_active() call release_pages() directly to avoid
296 * mutual recursion.
297 */
298 void __pagevec_release(struct pagevec *pvec)
299 {
300 lru_add_drain();
301 release_pages(pvec->pages, pagevec_count(pvec), pvec->cold);
302 pagevec_reinit(pvec);
303 }
304
305 EXPORT_SYMBOL(__pagevec_release);
306
307 /*
308 * pagevec_release() for pages which are known to not be on the LRU
309 *
310 * This function reinitialises the caller's pagevec.
311 */
312 void __pagevec_release_nonlru(struct pagevec *pvec)
313 {
314 int i;
315 struct pagevec pages_to_free;
316
317 pagevec_init(&pages_to_free, pvec->cold);
318 for (i = 0; i < pagevec_count(pvec); i++) {
319 struct page *page = pvec->pages[i];
320
321 BUG_ON(PageLRU(page));
322 if (put_page_testzero(page))
323 pagevec_add(&pages_to_free, page);
324 }
325 pagevec_free(&pages_to_free);
326 pagevec_reinit(pvec);
327 }
328
329 /*
330 * Add the passed pages to the LRU, then drop the caller's refcount
331 * on them. Reinitialises the caller's pagevec.
332 */
333 void __pagevec_lru_add(struct pagevec *pvec)
334 {
335 int i;
336 struct zone *zone = NULL;
337
338 for (i = 0; i < pagevec_count(pvec); i++) {
339 struct page *page = pvec->pages[i];
340 struct zone *pagezone = page_zone(page);
341
342 if (pagezone != zone) {
343 if (zone)
344 spin_unlock_irq(&zone->lru_lock);
345 zone = pagezone;
346 spin_lock_irq(&zone->lru_lock);
347 }
348 BUG_ON(PageLRU(page));
349 SetPageLRU(page);
350 add_page_to_inactive_list(zone, page);
351 }
352 if (zone)
353 spin_unlock_irq(&zone->lru_lock);
354 release_pages(pvec->pages, pvec->nr, pvec->cold);
355 pagevec_reinit(pvec);
356 }
357
358 EXPORT_SYMBOL(__pagevec_lru_add);
359
360 void __pagevec_lru_add_active(struct pagevec *pvec)
361 {
362 int i;
363 struct zone *zone = NULL;
364
365 for (i = 0; i < pagevec_count(pvec); i++) {
366 struct page *page = pvec->pages[i];
367 struct zone *pagezone = page_zone(page);
368
369 if (pagezone != zone) {
370 if (zone)
371 spin_unlock_irq(&zone->lru_lock);
372 zone = pagezone;
373 spin_lock_irq(&zone->lru_lock);
374 }
375 BUG_ON(PageLRU(page));
376 SetPageLRU(page);
377 BUG_ON(PageActive(page));
378 SetPageActive(page);
379 add_page_to_active_list(zone, page);
380 }
381 if (zone)
382 spin_unlock_irq(&zone->lru_lock);
383 release_pages(pvec->pages, pvec->nr, pvec->cold);
384 pagevec_reinit(pvec);
385 }
386
387 /*
388 * Try to drop buffers from the pages in a pagevec
389 */
390 void pagevec_strip(struct pagevec *pvec)
391 {
392 int i;
393
394 for (i = 0; i < pagevec_count(pvec); i++) {
395 struct page *page = pvec->pages[i];
396
397 if (PagePrivate(page) && !TestSetPageLocked(page)) {
398 if (PagePrivate(page))
399 try_to_release_page(page, 0);
400 unlock_page(page);
401 }
402 }
403 }
404
405 /**
406 * pagevec_lookup - gang pagecache lookup
407 * @pvec: Where the resulting pages are placed
408 * @mapping: The address_space to search
409 * @start: The starting page index
410 * @nr_pages: The maximum number of pages
411 *
412 * pagevec_lookup() will search for and return a group of up to @nr_pages pages
413 * in the mapping. The pages are placed in @pvec. pagevec_lookup() takes a
414 * reference against the pages in @pvec.
415 *
416 * The search returns a group of mapping-contiguous pages with ascending
417 * indexes. There may be holes in the indices due to not-present pages.
418 *
419 * pagevec_lookup() returns the number of pages which were found.
420 */
421 unsigned pagevec_lookup(struct pagevec *pvec, struct address_space *mapping,
422 pgoff_t start, unsigned nr_pages)
423 {
424 pvec->nr = find_get_pages(mapping, start, nr_pages, pvec->pages);
425 return pagevec_count(pvec);
426 }
427
428 EXPORT_SYMBOL(pagevec_lookup);
429
430 unsigned pagevec_lookup_tag(struct pagevec *pvec, struct address_space *mapping,
431 pgoff_t *index, int tag, unsigned nr_pages)
432 {
433 pvec->nr = find_get_pages_tag(mapping, index, tag,
434 nr_pages, pvec->pages);
435 return pagevec_count(pvec);
436 }
437
438 EXPORT_SYMBOL(pagevec_lookup_tag);
439
440 #ifdef CONFIG_SMP
441 /*
442 * We tolerate a little inaccuracy to avoid ping-ponging the counter between
443 * CPUs
444 */
445 #define ACCT_THRESHOLD max(16, NR_CPUS * 2)
446
447 static DEFINE_PER_CPU(long, committed_space) = 0;
448
449 void vm_acct_memory(long pages)
450 {
451 long *local;
452
453 preempt_disable();
454 local = &__get_cpu_var(committed_space);
455 *local += pages;
456 if (*local > ACCT_THRESHOLD || *local < -ACCT_THRESHOLD) {
457 atomic_add(*local, &vm_committed_space);
458 *local = 0;
459 }
460 preempt_enable();
461 }
462
463 #ifdef CONFIG_HOTPLUG_CPU
464
465 /* Drop the CPU's cached committed space back into the central pool. */
466 static int cpu_swap_callback(struct notifier_block *nfb,
467 unsigned long action,
468 void *hcpu)
469 {
470 long *committed;
471
472 committed = &per_cpu(committed_space, (long)hcpu);
473 if (action == CPU_DEAD) {
474 atomic_add(*committed, &vm_committed_space);
475 *committed = 0;
476 __lru_add_drain((long)hcpu);
477 }
478 return NOTIFY_OK;
479 }
480 #endif /* CONFIG_HOTPLUG_CPU */
481 #endif /* CONFIG_SMP */
482
483 #ifdef CONFIG_SMP
484 void percpu_counter_mod(struct percpu_counter *fbc, long amount)
485 {
486 long count;
487 long *pcount;
488 int cpu = get_cpu();
489
490 pcount = per_cpu_ptr(fbc->counters, cpu);
491 count = *pcount + amount;
492 if (count >= FBC_BATCH || count <= -FBC_BATCH) {
493 spin_lock(&fbc->lock);
494 fbc->count += count;
495 *pcount = 0;
496 spin_unlock(&fbc->lock);
497 } else {
498 *pcount = count;
499 }
500 put_cpu();
501 }
502 EXPORT_SYMBOL(percpu_counter_mod);
503
504 /*
505 * Add up all the per-cpu counts, return the result. This is a more accurate
506 * but much slower version of percpu_counter_read_positive()
507 */
508 long percpu_counter_sum(struct percpu_counter *fbc)
509 {
510 long ret;
511 int cpu;
512
513 spin_lock(&fbc->lock);
514 ret = fbc->count;
515 for_each_possible_cpu(cpu) {
516 long *pcount = per_cpu_ptr(fbc->counters, cpu);
517 ret += *pcount;
518 }
519 spin_unlock(&fbc->lock);
520 return ret < 0 ? 0 : ret;
521 }
522 EXPORT_SYMBOL(percpu_counter_sum);
523 #endif
524
525 /*
526 * Perform any setup for the swap system
527 */
528 void __init swap_setup(void)
529 {
530 unsigned long megs = num_physpages >> (20 - PAGE_SHIFT);
531
532 /* Use a smaller cluster for small-memory machines */
533 if (megs < 16)
534 page_cluster = 2;
535 else
536 page_cluster = 3;
537 /*
538 * Right now other parts of the system means that we
539 * _really_ don't want to cluster much more
540 */
541 hotcpu_notifier(cpu_swap_callback, 0);
542 }
543
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