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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)) {
Akinobu Mita1bfba4e2006-06-26 00:24:40 -070089 list_move_tail(&page->lru, &zone->inactive_list);
Linus Torvalds1da177e2005-04-16 15:20:36 -070090 inc_page_state(pgrotated);
91 }
92 if (!test_clear_page_writeback(page))
93 BUG();
94 spin_unlock_irqrestore(&zone->lru_lock, flags);
95 return 0;
96}
97
98/*
99 * FIXME: speed this up?
100 */
101void fastcall activate_page(struct page *page)
102{
103 struct zone *zone = page_zone(page);
104
105 spin_lock_irq(&zone->lru_lock);
106 if (PageLRU(page) && !PageActive(page)) {
107 del_page_from_inactive_list(zone, page);
108 SetPageActive(page);
109 add_page_to_active_list(zone, page);
110 inc_page_state(pgactivate);
111 }
112 spin_unlock_irq(&zone->lru_lock);
113}
114
115/*
116 * Mark a page as having seen activity.
117 *
118 * inactive,unreferenced -> inactive,referenced
119 * inactive,referenced -> active,unreferenced
120 * active,unreferenced -> active,referenced
121 */
122void fastcall mark_page_accessed(struct page *page)
123{
124 if (!PageActive(page) && PageReferenced(page) && PageLRU(page)) {
125 activate_page(page);
126 ClearPageReferenced(page);
127 } else if (!PageReferenced(page)) {
128 SetPageReferenced(page);
129 }
130}
131
132EXPORT_SYMBOL(mark_page_accessed);
133
134/**
135 * lru_cache_add: add a page to the page lists
136 * @page: the page to add
137 */
138static DEFINE_PER_CPU(struct pagevec, lru_add_pvecs) = { 0, };
139static DEFINE_PER_CPU(struct pagevec, lru_add_active_pvecs) = { 0, };
140
141void fastcall lru_cache_add(struct page *page)
142{
143 struct pagevec *pvec = &get_cpu_var(lru_add_pvecs);
144
145 page_cache_get(page);
146 if (!pagevec_add(pvec, page))
147 __pagevec_lru_add(pvec);
148 put_cpu_var(lru_add_pvecs);
149}
150
151void fastcall lru_cache_add_active(struct page *page)
152{
153 struct pagevec *pvec = &get_cpu_var(lru_add_active_pvecs);
154
155 page_cache_get(page);
156 if (!pagevec_add(pvec, page))
157 __pagevec_lru_add_active(pvec);
158 put_cpu_var(lru_add_active_pvecs);
159}
160
Andrew Morton80bfed92006-01-06 00:11:14 -0800161static void __lru_add_drain(int cpu)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700162{
Andrew Morton80bfed92006-01-06 00:11:14 -0800163 struct pagevec *pvec = &per_cpu(lru_add_pvecs, cpu);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700164
Andrew Morton80bfed92006-01-06 00:11:14 -0800165 /* CPU is dead, so no locking needed. */
Linus Torvalds1da177e2005-04-16 15:20:36 -0700166 if (pagevec_count(pvec))
167 __pagevec_lru_add(pvec);
Andrew Morton80bfed92006-01-06 00:11:14 -0800168 pvec = &per_cpu(lru_add_active_pvecs, cpu);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700169 if (pagevec_count(pvec))
170 __pagevec_lru_add_active(pvec);
Andrew Morton80bfed92006-01-06 00:11:14 -0800171}
172
173void lru_add_drain(void)
174{
175 __lru_add_drain(get_cpu());
176 put_cpu();
Linus Torvalds1da177e2005-04-16 15:20:36 -0700177}
178
Nick Piggin053837f2006-01-18 17:42:27 -0800179#ifdef CONFIG_NUMA
180static void lru_add_drain_per_cpu(void *dummy)
181{
182 lru_add_drain();
183}
184
185/*
186 * Returns 0 for success
187 */
188int lru_add_drain_all(void)
189{
190 return schedule_on_each_cpu(lru_add_drain_per_cpu, NULL);
191}
192
193#else
194
195/*
196 * Returns 0 for success
197 */
198int lru_add_drain_all(void)
199{
200 lru_add_drain();
201 return 0;
202}
203#endif
204
Linus Torvalds1da177e2005-04-16 15:20:36 -0700205/*
206 * This path almost never happens for VM activity - pages are normally
207 * freed via pagevecs. But it gets used by networking.
208 */
209void fastcall __page_cache_release(struct page *page)
210{
Nick Piggin46453a62006-03-22 00:07:58 -0800211 if (PageLRU(page)) {
212 unsigned long flags;
213 struct zone *zone = page_zone(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700214
Nick Piggin46453a62006-03-22 00:07:58 -0800215 spin_lock_irqsave(&zone->lru_lock, flags);
Nick Piggin8d438f92006-03-22 00:07:59 -0800216 BUG_ON(!PageLRU(page));
Nick Piggin67453912006-03-22 00:08:00 -0800217 __ClearPageLRU(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700218 del_page_from_lru(zone, page);
Nick Piggin46453a62006-03-22 00:07:58 -0800219 spin_unlock_irqrestore(&zone->lru_lock, flags);
220 }
221 free_hot_page(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700222}
Linus Torvalds1da177e2005-04-16 15:20:36 -0700223EXPORT_SYMBOL(__page_cache_release);
224
225/*
226 * Batched page_cache_release(). Decrement the reference count on all the
227 * passed pages. If it fell to zero then remove the page from the LRU and
228 * free it.
229 *
230 * Avoid taking zone->lru_lock if possible, but if it is taken, retain it
231 * for the remainder of the operation.
232 *
233 * The locking in this function is against shrink_cache(): we recheck the
234 * page count inside the lock to see whether shrink_cache grabbed the page
235 * via the LRU. If it did, give up: shrink_cache will free it.
236 */
237void release_pages(struct page **pages, int nr, int cold)
238{
239 int i;
240 struct pagevec pages_to_free;
241 struct zone *zone = NULL;
242
243 pagevec_init(&pages_to_free, cold);
244 for (i = 0; i < nr; i++) {
245 struct page *page = pages[i];
Linus Torvalds1da177e2005-04-16 15:20:36 -0700246
Nick Piggin8519fb32006-02-07 12:58:52 -0800247 if (unlikely(PageCompound(page))) {
248 if (zone) {
249 spin_unlock_irq(&zone->lru_lock);
250 zone = NULL;
251 }
252 put_compound_page(page);
253 continue;
254 }
255
Nick Pigginb5810032005-10-29 18:16:12 -0700256 if (!put_page_testzero(page))
Linus Torvalds1da177e2005-04-16 15:20:36 -0700257 continue;
258
Nick Piggin46453a62006-03-22 00:07:58 -0800259 if (PageLRU(page)) {
260 struct zone *pagezone = page_zone(page);
261 if (pagezone != zone) {
262 if (zone)
263 spin_unlock_irq(&zone->lru_lock);
264 zone = pagezone;
265 spin_lock_irq(&zone->lru_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700266 }
Nick Piggin8d438f92006-03-22 00:07:59 -0800267 BUG_ON(!PageLRU(page));
Nick Piggin67453912006-03-22 00:08:00 -0800268 __ClearPageLRU(page);
Nick Piggin46453a62006-03-22 00:07:58 -0800269 del_page_from_lru(zone, page);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700270 }
Nick Piggin46453a62006-03-22 00:07:58 -0800271
272 if (!pagevec_add(&pages_to_free, page)) {
273 if (zone) {
274 spin_unlock_irq(&zone->lru_lock);
275 zone = NULL;
276 }
277 __pagevec_free(&pages_to_free);
278 pagevec_reinit(&pages_to_free);
279 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700280 }
281 if (zone)
282 spin_unlock_irq(&zone->lru_lock);
283
284 pagevec_free(&pages_to_free);
285}
286
287/*
288 * The pages which we're about to release may be in the deferred lru-addition
289 * queues. That would prevent them from really being freed right now. That's
290 * OK from a correctness point of view but is inefficient - those pages may be
291 * cache-warm and we want to give them back to the page allocator ASAP.
292 *
293 * So __pagevec_release() will drain those queues here. __pagevec_lru_add()
294 * and __pagevec_lru_add_active() call release_pages() directly to avoid
295 * mutual recursion.
296 */
297void __pagevec_release(struct pagevec *pvec)
298{
299 lru_add_drain();
300 release_pages(pvec->pages, pagevec_count(pvec), pvec->cold);
301 pagevec_reinit(pvec);
302}
303
Steve French7f285702005-11-01 10:22:55 -0800304EXPORT_SYMBOL(__pagevec_release);
305
Linus Torvalds1da177e2005-04-16 15:20:36 -0700306/*
307 * pagevec_release() for pages which are known to not be on the LRU
308 *
309 * This function reinitialises the caller's pagevec.
310 */
311void __pagevec_release_nonlru(struct pagevec *pvec)
312{
313 int i;
314 struct pagevec pages_to_free;
315
316 pagevec_init(&pages_to_free, pvec->cold);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700317 for (i = 0; i < pagevec_count(pvec); i++) {
318 struct page *page = pvec->pages[i];
319
320 BUG_ON(PageLRU(page));
321 if (put_page_testzero(page))
322 pagevec_add(&pages_to_free, page);
323 }
324 pagevec_free(&pages_to_free);
325 pagevec_reinit(pvec);
326}
327
328/*
329 * Add the passed pages to the LRU, then drop the caller's refcount
330 * on them. Reinitialises the caller's pagevec.
331 */
332void __pagevec_lru_add(struct pagevec *pvec)
333{
334 int i;
335 struct zone *zone = NULL;
336
337 for (i = 0; i < pagevec_count(pvec); i++) {
338 struct page *page = pvec->pages[i];
339 struct zone *pagezone = page_zone(page);
340
341 if (pagezone != zone) {
342 if (zone)
343 spin_unlock_irq(&zone->lru_lock);
344 zone = pagezone;
345 spin_lock_irq(&zone->lru_lock);
346 }
Nick Piggin8d438f92006-03-22 00:07:59 -0800347 BUG_ON(PageLRU(page));
348 SetPageLRU(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700349 add_page_to_inactive_list(zone, page);
350 }
351 if (zone)
352 spin_unlock_irq(&zone->lru_lock);
353 release_pages(pvec->pages, pvec->nr, pvec->cold);
354 pagevec_reinit(pvec);
355}
356
357EXPORT_SYMBOL(__pagevec_lru_add);
358
359void __pagevec_lru_add_active(struct pagevec *pvec)
360{
361 int i;
362 struct zone *zone = NULL;
363
364 for (i = 0; i < pagevec_count(pvec); i++) {
365 struct page *page = pvec->pages[i];
366 struct zone *pagezone = page_zone(page);
367
368 if (pagezone != zone) {
369 if (zone)
370 spin_unlock_irq(&zone->lru_lock);
371 zone = pagezone;
372 spin_lock_irq(&zone->lru_lock);
373 }
Nick Piggin8d438f92006-03-22 00:07:59 -0800374 BUG_ON(PageLRU(page));
375 SetPageLRU(page);
Nick Piggin4c84cac2006-03-22 00:08:00 -0800376 BUG_ON(PageActive(page));
377 SetPageActive(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700378 add_page_to_active_list(zone, page);
379 }
380 if (zone)
381 spin_unlock_irq(&zone->lru_lock);
382 release_pages(pvec->pages, pvec->nr, pvec->cold);
383 pagevec_reinit(pvec);
384}
385
386/*
387 * Try to drop buffers from the pages in a pagevec
388 */
389void pagevec_strip(struct pagevec *pvec)
390{
391 int i;
392
393 for (i = 0; i < pagevec_count(pvec); i++) {
394 struct page *page = pvec->pages[i];
395
396 if (PagePrivate(page) && !TestSetPageLocked(page)) {
Christoph Lameter5b40dc72006-03-16 23:04:07 -0800397 if (PagePrivate(page))
398 try_to_release_page(page, 0);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700399 unlock_page(page);
400 }
401 }
402}
403
404/**
405 * pagevec_lookup - gang pagecache lookup
406 * @pvec: Where the resulting pages are placed
407 * @mapping: The address_space to search
408 * @start: The starting page index
409 * @nr_pages: The maximum number of pages
410 *
411 * pagevec_lookup() will search for and return a group of up to @nr_pages pages
412 * in the mapping. The pages are placed in @pvec. pagevec_lookup() takes a
413 * reference against the pages in @pvec.
414 *
415 * The search returns a group of mapping-contiguous pages with ascending
416 * indexes. There may be holes in the indices due to not-present pages.
417 *
418 * pagevec_lookup() returns the number of pages which were found.
419 */
420unsigned pagevec_lookup(struct pagevec *pvec, struct address_space *mapping,
421 pgoff_t start, unsigned nr_pages)
422{
423 pvec->nr = find_get_pages(mapping, start, nr_pages, pvec->pages);
424 return pagevec_count(pvec);
425}
426
Christoph Hellwig78539fd2006-01-11 20:47:41 +1100427EXPORT_SYMBOL(pagevec_lookup);
428
Linus Torvalds1da177e2005-04-16 15:20:36 -0700429unsigned pagevec_lookup_tag(struct pagevec *pvec, struct address_space *mapping,
430 pgoff_t *index, int tag, unsigned nr_pages)
431{
432 pvec->nr = find_get_pages_tag(mapping, index, tag,
433 nr_pages, pvec->pages);
434 return pagevec_count(pvec);
435}
436
Steve French7f285702005-11-01 10:22:55 -0800437EXPORT_SYMBOL(pagevec_lookup_tag);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700438
439#ifdef CONFIG_SMP
440/*
441 * We tolerate a little inaccuracy to avoid ping-ponging the counter between
442 * CPUs
443 */
444#define ACCT_THRESHOLD max(16, NR_CPUS * 2)
445
446static DEFINE_PER_CPU(long, committed_space) = 0;
447
448void vm_acct_memory(long pages)
449{
450 long *local;
451
452 preempt_disable();
453 local = &__get_cpu_var(committed_space);
454 *local += pages;
455 if (*local > ACCT_THRESHOLD || *local < -ACCT_THRESHOLD) {
456 atomic_add(*local, &vm_committed_space);
457 *local = 0;
458 }
459 preempt_enable();
460}
Linus Torvalds1da177e2005-04-16 15:20:36 -0700461
462#ifdef CONFIG_HOTPLUG_CPU
Linus Torvalds1da177e2005-04-16 15:20:36 -0700463
464/* Drop the CPU's cached committed space back into the central pool. */
465static int cpu_swap_callback(struct notifier_block *nfb,
466 unsigned long action,
467 void *hcpu)
468{
469 long *committed;
470
471 committed = &per_cpu(committed_space, (long)hcpu);
472 if (action == CPU_DEAD) {
473 atomic_add(*committed, &vm_committed_space);
474 *committed = 0;
Andrew Morton80bfed92006-01-06 00:11:14 -0800475 __lru_add_drain((long)hcpu);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700476 }
477 return NOTIFY_OK;
478}
479#endif /* CONFIG_HOTPLUG_CPU */
480#endif /* CONFIG_SMP */
481
Linus Torvalds1da177e2005-04-16 15:20:36 -0700482/*
483 * Perform any setup for the swap system
484 */
485void __init swap_setup(void)
486{
487 unsigned long megs = num_physpages >> (20 - PAGE_SHIFT);
488
489 /* Use a smaller cluster for small-memory machines */
490 if (megs < 16)
491 page_cluster = 2;
492 else
493 page_cluster = 3;
494 /*
495 * Right now other parts of the system means that we
496 * _really_ don't want to cluster much more
497 */
498 hotcpu_notifier(cpu_swap_callback, 0);
499}