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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
37#ifdef CONFIG_HUGETLB_PAGE
38
39void put_page(struct page *page)
40{
41 if (unlikely(PageCompound(page))) {
Hugh Dickins4c21e2f2005-10-29 18:16:40 -070042 page = (struct page *)page_private(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -070043 if (put_page_testzero(page)) {
44 void (*dtor)(struct page *page);
45
46 dtor = (void (*)(struct page *))page[1].mapping;
47 (*dtor)(page);
48 }
49 return;
50 }
Nick Pigginb5810032005-10-29 18:16:12 -070051 if (put_page_testzero(page))
Linus Torvalds1da177e2005-04-16 15:20:36 -070052 __page_cache_release(page);
53}
54EXPORT_SYMBOL(put_page);
55#endif
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 */
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
162void lru_add_drain(void)
163{
164 struct pagevec *pvec = &get_cpu_var(lru_add_pvecs);
165
166 if (pagevec_count(pvec))
167 __pagevec_lru_add(pvec);
168 pvec = &__get_cpu_var(lru_add_active_pvecs);
169 if (pagevec_count(pvec))
170 __pagevec_lru_add_active(pvec);
171 put_cpu_var(lru_add_pvecs);
172}
173
174/*
175 * This path almost never happens for VM activity - pages are normally
176 * freed via pagevecs. But it gets used by networking.
177 */
178void fastcall __page_cache_release(struct page *page)
179{
180 unsigned long flags;
181 struct zone *zone = page_zone(page);
182
183 spin_lock_irqsave(&zone->lru_lock, flags);
184 if (TestClearPageLRU(page))
185 del_page_from_lru(zone, page);
186 if (page_count(page) != 0)
187 page = NULL;
188 spin_unlock_irqrestore(&zone->lru_lock, flags);
189 if (page)
190 free_hot_page(page);
191}
192
193EXPORT_SYMBOL(__page_cache_release);
194
195/*
196 * Batched page_cache_release(). Decrement the reference count on all the
197 * passed pages. If it fell to zero then remove the page from the LRU and
198 * free it.
199 *
200 * Avoid taking zone->lru_lock if possible, but if it is taken, retain it
201 * for the remainder of the operation.
202 *
203 * The locking in this function is against shrink_cache(): we recheck the
204 * page count inside the lock to see whether shrink_cache grabbed the page
205 * via the LRU. If it did, give up: shrink_cache will free it.
206 */
207void release_pages(struct page **pages, int nr, int cold)
208{
209 int i;
210 struct pagevec pages_to_free;
211 struct zone *zone = NULL;
212
213 pagevec_init(&pages_to_free, cold);
214 for (i = 0; i < nr; i++) {
215 struct page *page = pages[i];
216 struct zone *pagezone;
217
Nick Pigginb5810032005-10-29 18:16:12 -0700218 if (!put_page_testzero(page))
Linus Torvalds1da177e2005-04-16 15:20:36 -0700219 continue;
220
221 pagezone = page_zone(page);
222 if (pagezone != zone) {
223 if (zone)
224 spin_unlock_irq(&zone->lru_lock);
225 zone = pagezone;
226 spin_lock_irq(&zone->lru_lock);
227 }
228 if (TestClearPageLRU(page))
229 del_page_from_lru(zone, page);
230 if (page_count(page) == 0) {
231 if (!pagevec_add(&pages_to_free, page)) {
232 spin_unlock_irq(&zone->lru_lock);
233 __pagevec_free(&pages_to_free);
234 pagevec_reinit(&pages_to_free);
235 zone = NULL; /* No lock is held */
236 }
237 }
238 }
239 if (zone)
240 spin_unlock_irq(&zone->lru_lock);
241
242 pagevec_free(&pages_to_free);
243}
244
245/*
246 * The pages which we're about to release may be in the deferred lru-addition
247 * queues. That would prevent them from really being freed right now. That's
248 * OK from a correctness point of view but is inefficient - those pages may be
249 * cache-warm and we want to give them back to the page allocator ASAP.
250 *
251 * So __pagevec_release() will drain those queues here. __pagevec_lru_add()
252 * and __pagevec_lru_add_active() call release_pages() directly to avoid
253 * mutual recursion.
254 */
255void __pagevec_release(struct pagevec *pvec)
256{
257 lru_add_drain();
258 release_pages(pvec->pages, pagevec_count(pvec), pvec->cold);
259 pagevec_reinit(pvec);
260}
261
Steve French7f285702005-11-01 10:22:55 -0800262EXPORT_SYMBOL(__pagevec_release);
263
Linus Torvalds1da177e2005-04-16 15:20:36 -0700264/*
265 * pagevec_release() for pages which are known to not be on the LRU
266 *
267 * This function reinitialises the caller's pagevec.
268 */
269void __pagevec_release_nonlru(struct pagevec *pvec)
270{
271 int i;
272 struct pagevec pages_to_free;
273
274 pagevec_init(&pages_to_free, pvec->cold);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700275 for (i = 0; i < pagevec_count(pvec); i++) {
276 struct page *page = pvec->pages[i];
277
278 BUG_ON(PageLRU(page));
279 if (put_page_testzero(page))
280 pagevec_add(&pages_to_free, page);
281 }
282 pagevec_free(&pages_to_free);
283 pagevec_reinit(pvec);
284}
285
286/*
287 * Add the passed pages to the LRU, then drop the caller's refcount
288 * on them. Reinitialises the caller's pagevec.
289 */
290void __pagevec_lru_add(struct pagevec *pvec)
291{
292 int i;
293 struct zone *zone = NULL;
294
295 for (i = 0; i < pagevec_count(pvec); i++) {
296 struct page *page = pvec->pages[i];
297 struct zone *pagezone = page_zone(page);
298
299 if (pagezone != zone) {
300 if (zone)
301 spin_unlock_irq(&zone->lru_lock);
302 zone = pagezone;
303 spin_lock_irq(&zone->lru_lock);
304 }
305 if (TestSetPageLRU(page))
306 BUG();
307 add_page_to_inactive_list(zone, page);
308 }
309 if (zone)
310 spin_unlock_irq(&zone->lru_lock);
311 release_pages(pvec->pages, pvec->nr, pvec->cold);
312 pagevec_reinit(pvec);
313}
314
315EXPORT_SYMBOL(__pagevec_lru_add);
316
317void __pagevec_lru_add_active(struct pagevec *pvec)
318{
319 int i;
320 struct zone *zone = NULL;
321
322 for (i = 0; i < pagevec_count(pvec); i++) {
323 struct page *page = pvec->pages[i];
324 struct zone *pagezone = page_zone(page);
325
326 if (pagezone != zone) {
327 if (zone)
328 spin_unlock_irq(&zone->lru_lock);
329 zone = pagezone;
330 spin_lock_irq(&zone->lru_lock);
331 }
332 if (TestSetPageLRU(page))
333 BUG();
334 if (TestSetPageActive(page))
335 BUG();
336 add_page_to_active_list(zone, page);
337 }
338 if (zone)
339 spin_unlock_irq(&zone->lru_lock);
340 release_pages(pvec->pages, pvec->nr, pvec->cold);
341 pagevec_reinit(pvec);
342}
343
344/*
345 * Try to drop buffers from the pages in a pagevec
346 */
347void pagevec_strip(struct pagevec *pvec)
348{
349 int i;
350
351 for (i = 0; i < pagevec_count(pvec); i++) {
352 struct page *page = pvec->pages[i];
353
354 if (PagePrivate(page) && !TestSetPageLocked(page)) {
355 try_to_release_page(page, 0);
356 unlock_page(page);
357 }
358 }
359}
360
361/**
362 * pagevec_lookup - gang pagecache lookup
363 * @pvec: Where the resulting pages are placed
364 * @mapping: The address_space to search
365 * @start: The starting page index
366 * @nr_pages: The maximum number of pages
367 *
368 * pagevec_lookup() will search for and return a group of up to @nr_pages pages
369 * in the mapping. The pages are placed in @pvec. pagevec_lookup() takes a
370 * reference against the pages in @pvec.
371 *
372 * The search returns a group of mapping-contiguous pages with ascending
373 * indexes. There may be holes in the indices due to not-present pages.
374 *
375 * pagevec_lookup() returns the number of pages which were found.
376 */
377unsigned pagevec_lookup(struct pagevec *pvec, struct address_space *mapping,
378 pgoff_t start, unsigned nr_pages)
379{
380 pvec->nr = find_get_pages(mapping, start, nr_pages, pvec->pages);
381 return pagevec_count(pvec);
382}
383
384unsigned pagevec_lookup_tag(struct pagevec *pvec, struct address_space *mapping,
385 pgoff_t *index, int tag, unsigned nr_pages)
386{
387 pvec->nr = find_get_pages_tag(mapping, index, tag,
388 nr_pages, pvec->pages);
389 return pagevec_count(pvec);
390}
391
Steve French7f285702005-11-01 10:22:55 -0800392EXPORT_SYMBOL(pagevec_lookup_tag);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700393
394#ifdef CONFIG_SMP
395/*
396 * We tolerate a little inaccuracy to avoid ping-ponging the counter between
397 * CPUs
398 */
399#define ACCT_THRESHOLD max(16, NR_CPUS * 2)
400
401static DEFINE_PER_CPU(long, committed_space) = 0;
402
403void vm_acct_memory(long pages)
404{
405 long *local;
406
407 preempt_disable();
408 local = &__get_cpu_var(committed_space);
409 *local += pages;
410 if (*local > ACCT_THRESHOLD || *local < -ACCT_THRESHOLD) {
411 atomic_add(*local, &vm_committed_space);
412 *local = 0;
413 }
414 preempt_enable();
415}
Linus Torvalds1da177e2005-04-16 15:20:36 -0700416
417#ifdef CONFIG_HOTPLUG_CPU
418static void lru_drain_cache(unsigned int cpu)
419{
420 struct pagevec *pvec = &per_cpu(lru_add_pvecs, cpu);
421
422 /* CPU is dead, so no locking needed. */
423 if (pagevec_count(pvec))
424 __pagevec_lru_add(pvec);
425 pvec = &per_cpu(lru_add_active_pvecs, cpu);
426 if (pagevec_count(pvec))
427 __pagevec_lru_add_active(pvec);
428}
429
430/* Drop the CPU's cached committed space back into the central pool. */
431static int cpu_swap_callback(struct notifier_block *nfb,
432 unsigned long action,
433 void *hcpu)
434{
435 long *committed;
436
437 committed = &per_cpu(committed_space, (long)hcpu);
438 if (action == CPU_DEAD) {
439 atomic_add(*committed, &vm_committed_space);
440 *committed = 0;
441 lru_drain_cache((long)hcpu);
442 }
443 return NOTIFY_OK;
444}
445#endif /* CONFIG_HOTPLUG_CPU */
446#endif /* CONFIG_SMP */
447
448#ifdef CONFIG_SMP
449void percpu_counter_mod(struct percpu_counter *fbc, long amount)
450{
451 long count;
452 long *pcount;
453 int cpu = get_cpu();
454
455 pcount = per_cpu_ptr(fbc->counters, cpu);
456 count = *pcount + amount;
457 if (count >= FBC_BATCH || count <= -FBC_BATCH) {
458 spin_lock(&fbc->lock);
459 fbc->count += count;
460 spin_unlock(&fbc->lock);
461 count = 0;
462 }
463 *pcount = count;
464 put_cpu();
465}
466EXPORT_SYMBOL(percpu_counter_mod);
467#endif
468
469/*
470 * Perform any setup for the swap system
471 */
472void __init swap_setup(void)
473{
474 unsigned long megs = num_physpages >> (20 - PAGE_SHIFT);
475
476 /* Use a smaller cluster for small-memory machines */
477 if (megs < 16)
478 page_cluster = 2;
479 else
480 page_cluster = 3;
481 /*
482 * Right now other parts of the system means that we
483 * _really_ don't want to cluster much more
484 */
485 hotcpu_notifier(cpu_swap_callback, 0);
486}