xref: /openbmc/linux/mm/swap.c (revision d5cb9783536a41df9f9cba5b0a1d78047ed787f7)
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 #ifdef CONFIG_HUGETLB_PAGE
38 
39 void put_page(struct page *page)
40 {
41 	if (unlikely(PageCompound(page))) {
42 		page = (struct page *)page_private(page);
43 		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 	}
51 	if (put_page_testzero(page))
52 		__page_cache_release(page);
53 }
54 EXPORT_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  */
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 void 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  */
178 void 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 
193 EXPORT_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  */
207 void 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 
218 		if (!put_page_testzero(page))
219 			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  */
255 void __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 
262 EXPORT_SYMBOL(__pagevec_release);
263 
264 /*
265  * pagevec_release() for pages which are known to not be on the LRU
266  *
267  * This function reinitialises the caller's pagevec.
268  */
269 void __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);
275 	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  */
290 void __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 
315 EXPORT_SYMBOL(__pagevec_lru_add);
316 
317 void __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  */
347 void 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  */
377 unsigned 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 
384 unsigned 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 
392 EXPORT_SYMBOL(pagevec_lookup_tag);
393 
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 
401 static DEFINE_PER_CPU(long, committed_space) = 0;
402 
403 void 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 }
416 EXPORT_SYMBOL(vm_acct_memory);
417 
418 #ifdef CONFIG_HOTPLUG_CPU
419 static void lru_drain_cache(unsigned int cpu)
420 {
421 	struct pagevec *pvec = &per_cpu(lru_add_pvecs, cpu);
422 
423 	/* CPU is dead, so no locking needed. */
424 	if (pagevec_count(pvec))
425 		__pagevec_lru_add(pvec);
426 	pvec = &per_cpu(lru_add_active_pvecs, cpu);
427 	if (pagevec_count(pvec))
428 		__pagevec_lru_add_active(pvec);
429 }
430 
431 /* Drop the CPU's cached committed space back into the central pool. */
432 static int cpu_swap_callback(struct notifier_block *nfb,
433 			     unsigned long action,
434 			     void *hcpu)
435 {
436 	long *committed;
437 
438 	committed = &per_cpu(committed_space, (long)hcpu);
439 	if (action == CPU_DEAD) {
440 		atomic_add(*committed, &vm_committed_space);
441 		*committed = 0;
442 		lru_drain_cache((long)hcpu);
443 	}
444 	return NOTIFY_OK;
445 }
446 #endif /* CONFIG_HOTPLUG_CPU */
447 #endif /* CONFIG_SMP */
448 
449 #ifdef CONFIG_SMP
450 void percpu_counter_mod(struct percpu_counter *fbc, long amount)
451 {
452 	long count;
453 	long *pcount;
454 	int cpu = get_cpu();
455 
456 	pcount = per_cpu_ptr(fbc->counters, cpu);
457 	count = *pcount + amount;
458 	if (count >= FBC_BATCH || count <= -FBC_BATCH) {
459 		spin_lock(&fbc->lock);
460 		fbc->count += count;
461 		spin_unlock(&fbc->lock);
462 		count = 0;
463 	}
464 	*pcount = count;
465 	put_cpu();
466 }
467 EXPORT_SYMBOL(percpu_counter_mod);
468 #endif
469 
470 /*
471  * Perform any setup for the swap system
472  */
473 void __init swap_setup(void)
474 {
475 	unsigned long megs = num_physpages >> (20 - PAGE_SHIFT);
476 
477 	/* Use a smaller cluster for small-memory machines */
478 	if (megs < 16)
479 		page_cluster = 2;
480 	else
481 		page_cluster = 3;
482 	/*
483 	 * Right now other parts of the system means that we
484 	 * _really_ don't want to cluster much more
485 	 */
486 	hotcpu_notifier(cpu_swap_callback, 0);
487 }
488