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Linus Torvalds1da177e2005-04-16 15:20:36 -07001/*
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? */
35int page_cluster;
36
Nick Piggin8519fb32006-02-07 12:58:52 -080037static 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
Hugh Dickins41d78ba2006-02-14 13:52:58 -080043 dtor = (void (*)(struct page *))page[1].lru.next;
Nick Piggin8519fb32006-02-07 12:58:52 -080044 (*dtor)(page);
45 }
46}
47
Linus Torvalds1da177e2005-04-16 15:20:36 -070048void put_page(struct page *page)
49{
Nick Piggin8519fb32006-02-07 12:58:52 -080050 if (unlikely(PageCompound(page)))
51 put_compound_page(page);
52 else if (put_page_testzero(page))
Linus Torvalds1da177e2005-04-16 15:20:36 -070053 __page_cache_release(page);
54}
55EXPORT_SYMBOL(put_page);
Linus Torvalds1da177e2005-04-16 15:20:36 -070056
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 */
72int 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 */
102void 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 */
123void 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
133EXPORT_SYMBOL(mark_page_accessed);
134
135/**
136 * lru_cache_add: add a page to the page lists
137 * @page: the page to add
138 */
139static DEFINE_PER_CPU(struct pagevec, lru_add_pvecs) = { 0, };
140static DEFINE_PER_CPU(struct pagevec, lru_add_active_pvecs) = { 0, };
141
142void 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
152void 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
Andrew Morton80bfed92006-01-06 00:11:14 -0800162static void __lru_add_drain(int cpu)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700163{
Andrew Morton80bfed92006-01-06 00:11:14 -0800164 struct pagevec *pvec = &per_cpu(lru_add_pvecs, cpu);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700165
Andrew Morton80bfed92006-01-06 00:11:14 -0800166 /* CPU is dead, so no locking needed. */
Linus Torvalds1da177e2005-04-16 15:20:36 -0700167 if (pagevec_count(pvec))
168 __pagevec_lru_add(pvec);
Andrew Morton80bfed92006-01-06 00:11:14 -0800169 pvec = &per_cpu(lru_add_active_pvecs, cpu);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700170 if (pagevec_count(pvec))
171 __pagevec_lru_add_active(pvec);
Andrew Morton80bfed92006-01-06 00:11:14 -0800172}
173
174void lru_add_drain(void)
175{
176 __lru_add_drain(get_cpu());
177 put_cpu();
Linus Torvalds1da177e2005-04-16 15:20:36 -0700178}
179
Nick Piggin053837f2006-01-18 17:42:27 -0800180#ifdef CONFIG_NUMA
181static void lru_add_drain_per_cpu(void *dummy)
182{
183 lru_add_drain();
184}
185
186/*
187 * Returns 0 for success
188 */
189int 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 */
199int lru_add_drain_all(void)
200{
201 lru_add_drain();
202 return 0;
203}
204#endif
205
Linus Torvalds1da177e2005-04-16 15:20:36 -0700206/*
207 * This path almost never happens for VM activity - pages are normally
208 * freed via pagevecs. But it gets used by networking.
209 */
210void fastcall __page_cache_release(struct page *page)
211{
212 unsigned long flags;
213 struct zone *zone = page_zone(page);
214
215 spin_lock_irqsave(&zone->lru_lock, flags);
216 if (TestClearPageLRU(page))
217 del_page_from_lru(zone, page);
218 if (page_count(page) != 0)
219 page = NULL;
220 spin_unlock_irqrestore(&zone->lru_lock, flags);
221 if (page)
222 free_hot_page(page);
223}
224
225EXPORT_SYMBOL(__page_cache_release);
226
227/*
228 * Batched page_cache_release(). Decrement the reference count on all the
229 * passed pages. If it fell to zero then remove the page from the LRU and
230 * free it.
231 *
232 * Avoid taking zone->lru_lock if possible, but if it is taken, retain it
233 * for the remainder of the operation.
234 *
235 * The locking in this function is against shrink_cache(): we recheck the
236 * page count inside the lock to see whether shrink_cache grabbed the page
237 * via the LRU. If it did, give up: shrink_cache will free it.
238 */
239void release_pages(struct page **pages, int nr, int cold)
240{
241 int i;
242 struct pagevec pages_to_free;
243 struct zone *zone = NULL;
244
245 pagevec_init(&pages_to_free, cold);
246 for (i = 0; i < nr; i++) {
247 struct page *page = pages[i];
248 struct zone *pagezone;
249
Nick Piggin8519fb32006-02-07 12:58:52 -0800250 if (unlikely(PageCompound(page))) {
251 if (zone) {
252 spin_unlock_irq(&zone->lru_lock);
253 zone = NULL;
254 }
255 put_compound_page(page);
256 continue;
257 }
258
Nick Pigginb5810032005-10-29 18:16:12 -0700259 if (!put_page_testzero(page))
Linus Torvalds1da177e2005-04-16 15:20:36 -0700260 continue;
261
262 pagezone = page_zone(page);
263 if (pagezone != zone) {
264 if (zone)
265 spin_unlock_irq(&zone->lru_lock);
266 zone = pagezone;
267 spin_lock_irq(&zone->lru_lock);
268 }
269 if (TestClearPageLRU(page))
270 del_page_from_lru(zone, page);
271 if (page_count(page) == 0) {
272 if (!pagevec_add(&pages_to_free, page)) {
273 spin_unlock_irq(&zone->lru_lock);
274 __pagevec_free(&pages_to_free);
275 pagevec_reinit(&pages_to_free);
276 zone = NULL; /* No lock is held */
277 }
278 }
279 }
280 if (zone)
281 spin_unlock_irq(&zone->lru_lock);
282
283 pagevec_free(&pages_to_free);
284}
285
286/*
287 * The pages which we're about to release may be in the deferred lru-addition
288 * queues. That would prevent them from really being freed right now. That's
289 * OK from a correctness point of view but is inefficient - those pages may be
290 * cache-warm and we want to give them back to the page allocator ASAP.
291 *
292 * So __pagevec_release() will drain those queues here. __pagevec_lru_add()
293 * and __pagevec_lru_add_active() call release_pages() directly to avoid
294 * mutual recursion.
295 */
296void __pagevec_release(struct pagevec *pvec)
297{
298 lru_add_drain();
299 release_pages(pvec->pages, pagevec_count(pvec), pvec->cold);
300 pagevec_reinit(pvec);
301}
302
Steve French7f285702005-11-01 10:22:55 -0800303EXPORT_SYMBOL(__pagevec_release);
304
Linus Torvalds1da177e2005-04-16 15:20:36 -0700305/*
306 * pagevec_release() for pages which are known to not be on the LRU
307 *
308 * This function reinitialises the caller's pagevec.
309 */
310void __pagevec_release_nonlru(struct pagevec *pvec)
311{
312 int i;
313 struct pagevec pages_to_free;
314
315 pagevec_init(&pages_to_free, pvec->cold);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700316 for (i = 0; i < pagevec_count(pvec); i++) {
317 struct page *page = pvec->pages[i];
318
319 BUG_ON(PageLRU(page));
320 if (put_page_testzero(page))
321 pagevec_add(&pages_to_free, page);
322 }
323 pagevec_free(&pages_to_free);
324 pagevec_reinit(pvec);
325}
326
327/*
328 * Add the passed pages to the LRU, then drop the caller's refcount
329 * on them. Reinitialises the caller's pagevec.
330 */
331void __pagevec_lru_add(struct pagevec *pvec)
332{
333 int i;
334 struct zone *zone = NULL;
335
336 for (i = 0; i < pagevec_count(pvec); i++) {
337 struct page *page = pvec->pages[i];
338 struct zone *pagezone = page_zone(page);
339
340 if (pagezone != zone) {
341 if (zone)
342 spin_unlock_irq(&zone->lru_lock);
343 zone = pagezone;
344 spin_lock_irq(&zone->lru_lock);
345 }
346 if (TestSetPageLRU(page))
347 BUG();
348 add_page_to_inactive_list(zone, page);
349 }
350 if (zone)
351 spin_unlock_irq(&zone->lru_lock);
352 release_pages(pvec->pages, pvec->nr, pvec->cold);
353 pagevec_reinit(pvec);
354}
355
356EXPORT_SYMBOL(__pagevec_lru_add);
357
358void __pagevec_lru_add_active(struct pagevec *pvec)
359{
360 int i;
361 struct zone *zone = NULL;
362
363 for (i = 0; i < pagevec_count(pvec); i++) {
364 struct page *page = pvec->pages[i];
365 struct zone *pagezone = page_zone(page);
366
367 if (pagezone != zone) {
368 if (zone)
369 spin_unlock_irq(&zone->lru_lock);
370 zone = pagezone;
371 spin_lock_irq(&zone->lru_lock);
372 }
373 if (TestSetPageLRU(page))
374 BUG();
375 if (TestSetPageActive(page))
376 BUG();
377 add_page_to_active_list(zone, page);
378 }
379 if (zone)
380 spin_unlock_irq(&zone->lru_lock);
381 release_pages(pvec->pages, pvec->nr, pvec->cold);
382 pagevec_reinit(pvec);
383}
384
385/*
386 * Try to drop buffers from the pages in a pagevec
387 */
388void pagevec_strip(struct pagevec *pvec)
389{
390 int i;
391
392 for (i = 0; i < pagevec_count(pvec); i++) {
393 struct page *page = pvec->pages[i];
394
395 if (PagePrivate(page) && !TestSetPageLocked(page)) {
396 try_to_release_page(page, 0);
397 unlock_page(page);
398 }
399 }
400}
401
402/**
403 * pagevec_lookup - gang pagecache lookup
404 * @pvec: Where the resulting pages are placed
405 * @mapping: The address_space to search
406 * @start: The starting page index
407 * @nr_pages: The maximum number of pages
408 *
409 * pagevec_lookup() will search for and return a group of up to @nr_pages pages
410 * in the mapping. The pages are placed in @pvec. pagevec_lookup() takes a
411 * reference against the pages in @pvec.
412 *
413 * The search returns a group of mapping-contiguous pages with ascending
414 * indexes. There may be holes in the indices due to not-present pages.
415 *
416 * pagevec_lookup() returns the number of pages which were found.
417 */
418unsigned pagevec_lookup(struct pagevec *pvec, struct address_space *mapping,
419 pgoff_t start, unsigned nr_pages)
420{
421 pvec->nr = find_get_pages(mapping, start, nr_pages, pvec->pages);
422 return pagevec_count(pvec);
423}
424
Christoph Hellwig78539fd2006-01-11 20:47:41 +1100425EXPORT_SYMBOL(pagevec_lookup);
426
Linus Torvalds1da177e2005-04-16 15:20:36 -0700427unsigned pagevec_lookup_tag(struct pagevec *pvec, struct address_space *mapping,
428 pgoff_t *index, int tag, unsigned nr_pages)
429{
430 pvec->nr = find_get_pages_tag(mapping, index, tag,
431 nr_pages, pvec->pages);
432 return pagevec_count(pvec);
433}
434
Steve French7f285702005-11-01 10:22:55 -0800435EXPORT_SYMBOL(pagevec_lookup_tag);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700436
437#ifdef CONFIG_SMP
438/*
439 * We tolerate a little inaccuracy to avoid ping-ponging the counter between
440 * CPUs
441 */
442#define ACCT_THRESHOLD max(16, NR_CPUS * 2)
443
444static DEFINE_PER_CPU(long, committed_space) = 0;
445
446void vm_acct_memory(long pages)
447{
448 long *local;
449
450 preempt_disable();
451 local = &__get_cpu_var(committed_space);
452 *local += pages;
453 if (*local > ACCT_THRESHOLD || *local < -ACCT_THRESHOLD) {
454 atomic_add(*local, &vm_committed_space);
455 *local = 0;
456 }
457 preempt_enable();
458}
Linus Torvalds1da177e2005-04-16 15:20:36 -0700459
460#ifdef CONFIG_HOTPLUG_CPU
Linus Torvalds1da177e2005-04-16 15:20:36 -0700461
462/* Drop the CPU's cached committed space back into the central pool. */
463static int cpu_swap_callback(struct notifier_block *nfb,
464 unsigned long action,
465 void *hcpu)
466{
467 long *committed;
468
469 committed = &per_cpu(committed_space, (long)hcpu);
470 if (action == CPU_DEAD) {
471 atomic_add(*committed, &vm_committed_space);
472 *committed = 0;
Andrew Morton80bfed92006-01-06 00:11:14 -0800473 __lru_add_drain((long)hcpu);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700474 }
475 return NOTIFY_OK;
476}
477#endif /* CONFIG_HOTPLUG_CPU */
478#endif /* CONFIG_SMP */
479
480#ifdef CONFIG_SMP
481void percpu_counter_mod(struct percpu_counter *fbc, long amount)
482{
483 long count;
484 long *pcount;
485 int cpu = get_cpu();
486
487 pcount = per_cpu_ptr(fbc->counters, cpu);
488 count = *pcount + amount;
489 if (count >= FBC_BATCH || count <= -FBC_BATCH) {
490 spin_lock(&fbc->lock);
491 fbc->count += count;
Andrew Mortone2bab3d2006-03-07 21:55:31 -0800492 *pcount = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700493 spin_unlock(&fbc->lock);
Andrew Mortone2bab3d2006-03-07 21:55:31 -0800494 } else {
495 *pcount = count;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700496 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700497 put_cpu();
498}
499EXPORT_SYMBOL(percpu_counter_mod);
Andrew Mortone2bab3d2006-03-07 21:55:31 -0800500
501/*
502 * Add up all the per-cpu counts, return the result. This is a more accurate
503 * but much slower version of percpu_counter_read_positive()
504 */
505long percpu_counter_sum(struct percpu_counter *fbc)
506{
507 long ret;
508 int cpu;
509
510 spin_lock(&fbc->lock);
511 ret = fbc->count;
512 for_each_cpu(cpu) {
513 long *pcount = per_cpu_ptr(fbc->counters, cpu);
514 ret += *pcount;
515 }
516 spin_unlock(&fbc->lock);
517 return ret < 0 ? 0 : ret;
518}
519EXPORT_SYMBOL(percpu_counter_sum);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700520#endif
521
522/*
523 * Perform any setup for the swap system
524 */
525void __init swap_setup(void)
526{
527 unsigned long megs = num_physpages >> (20 - PAGE_SHIFT);
528
529 /* Use a smaller cluster for small-memory machines */
530 if (megs < 16)
531 page_cluster = 2;
532 else
533 page_cluster = 3;
534 /*
535 * Right now other parts of the system means that we
536 * _really_ don't want to cluster much more
537 */
538 hotcpu_notifier(cpu_swap_callback, 0);
539}