xref: /openbmc/linux/mm/swap.c (revision dbf563ee)
1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3  *  linux/mm/swap.c
4  *
5  *  Copyright (C) 1991, 1992, 1993, 1994  Linus Torvalds
6  */
7 
8 /*
9  * This file contains the default values for the operation of the
10  * Linux VM subsystem. Fine-tuning documentation can be found in
11  * Documentation/admin-guide/sysctl/vm.rst.
12  * Started 18.12.91
13  * Swap aging added 23.2.95, Stephen Tweedie.
14  * Buffermem limits added 12.3.98, Rik van Riel.
15  */
16 
17 #include <linux/mm.h>
18 #include <linux/sched.h>
19 #include <linux/kernel_stat.h>
20 #include <linux/swap.h>
21 #include <linux/mman.h>
22 #include <linux/pagemap.h>
23 #include <linux/pagevec.h>
24 #include <linux/init.h>
25 #include <linux/export.h>
26 #include <linux/mm_inline.h>
27 #include <linux/percpu_counter.h>
28 #include <linux/memremap.h>
29 #include <linux/percpu.h>
30 #include <linux/cpu.h>
31 #include <linux/notifier.h>
32 #include <linux/backing-dev.h>
33 #include <linux/memcontrol.h>
34 #include <linux/gfp.h>
35 #include <linux/uio.h>
36 #include <linux/hugetlb.h>
37 #include <linux/page_idle.h>
38 #include <linux/local_lock.h>
39 
40 #include "internal.h"
41 
42 #define CREATE_TRACE_POINTS
43 #include <trace/events/pagemap.h>
44 
45 /* How many pages do we try to swap or page in/out together? */
46 int page_cluster;
47 
48 /* Protecting only lru_rotate.pvec which requires disabling interrupts */
49 struct lru_rotate {
50 	local_lock_t lock;
51 	struct pagevec pvec;
52 };
53 static DEFINE_PER_CPU(struct lru_rotate, lru_rotate) = {
54 	.lock = INIT_LOCAL_LOCK(lock),
55 };
56 
57 /*
58  * The following struct pagevec are grouped together because they are protected
59  * by disabling preemption (and interrupts remain enabled).
60  */
61 struct lru_pvecs {
62 	local_lock_t lock;
63 	struct pagevec lru_add;
64 	struct pagevec lru_deactivate_file;
65 	struct pagevec lru_deactivate;
66 	struct pagevec lru_lazyfree;
67 #ifdef CONFIG_SMP
68 	struct pagevec activate_page;
69 #endif
70 };
71 static DEFINE_PER_CPU(struct lru_pvecs, lru_pvecs) = {
72 	.lock = INIT_LOCAL_LOCK(lock),
73 };
74 
75 /*
76  * This path almost never happens for VM activity - pages are normally
77  * freed via pagevecs.  But it gets used by networking.
78  */
79 static void __page_cache_release(struct page *page)
80 {
81 	if (PageLRU(page)) {
82 		pg_data_t *pgdat = page_pgdat(page);
83 		struct lruvec *lruvec;
84 		unsigned long flags;
85 
86 		spin_lock_irqsave(&pgdat->lru_lock, flags);
87 		lruvec = mem_cgroup_page_lruvec(page, pgdat);
88 		VM_BUG_ON_PAGE(!PageLRU(page), page);
89 		__ClearPageLRU(page);
90 		del_page_from_lru_list(page, lruvec, page_off_lru(page));
91 		spin_unlock_irqrestore(&pgdat->lru_lock, flags);
92 	}
93 	__ClearPageWaiters(page);
94 }
95 
96 static void __put_single_page(struct page *page)
97 {
98 	__page_cache_release(page);
99 	mem_cgroup_uncharge(page);
100 	free_unref_page(page);
101 }
102 
103 static void __put_compound_page(struct page *page)
104 {
105 	/*
106 	 * __page_cache_release() is supposed to be called for thp, not for
107 	 * hugetlb. This is because hugetlb page does never have PageLRU set
108 	 * (it's never listed to any LRU lists) and no memcg routines should
109 	 * be called for hugetlb (it has a separate hugetlb_cgroup.)
110 	 */
111 	if (!PageHuge(page))
112 		__page_cache_release(page);
113 	destroy_compound_page(page);
114 }
115 
116 void __put_page(struct page *page)
117 {
118 	if (is_zone_device_page(page)) {
119 		put_dev_pagemap(page->pgmap);
120 
121 		/*
122 		 * The page belongs to the device that created pgmap. Do
123 		 * not return it to page allocator.
124 		 */
125 		return;
126 	}
127 
128 	if (unlikely(PageCompound(page)))
129 		__put_compound_page(page);
130 	else
131 		__put_single_page(page);
132 }
133 EXPORT_SYMBOL(__put_page);
134 
135 /**
136  * put_pages_list() - release a list of pages
137  * @pages: list of pages threaded on page->lru
138  *
139  * Release a list of pages which are strung together on page.lru.  Currently
140  * used by read_cache_pages() and related error recovery code.
141  */
142 void put_pages_list(struct list_head *pages)
143 {
144 	while (!list_empty(pages)) {
145 		struct page *victim;
146 
147 		victim = lru_to_page(pages);
148 		list_del(&victim->lru);
149 		put_page(victim);
150 	}
151 }
152 EXPORT_SYMBOL(put_pages_list);
153 
154 /*
155  * get_kernel_pages() - pin kernel pages in memory
156  * @kiov:	An array of struct kvec structures
157  * @nr_segs:	number of segments to pin
158  * @write:	pinning for read/write, currently ignored
159  * @pages:	array that receives pointers to the pages pinned.
160  *		Should be at least nr_segs long.
161  *
162  * Returns number of pages pinned. This may be fewer than the number
163  * requested. If nr_pages is 0 or negative, returns 0. If no pages
164  * were pinned, returns -errno. Each page returned must be released
165  * with a put_page() call when it is finished with.
166  */
167 int get_kernel_pages(const struct kvec *kiov, int nr_segs, int write,
168 		struct page **pages)
169 {
170 	int seg;
171 
172 	for (seg = 0; seg < nr_segs; seg++) {
173 		if (WARN_ON(kiov[seg].iov_len != PAGE_SIZE))
174 			return seg;
175 
176 		pages[seg] = kmap_to_page(kiov[seg].iov_base);
177 		get_page(pages[seg]);
178 	}
179 
180 	return seg;
181 }
182 EXPORT_SYMBOL_GPL(get_kernel_pages);
183 
184 /*
185  * get_kernel_page() - pin a kernel page in memory
186  * @start:	starting kernel address
187  * @write:	pinning for read/write, currently ignored
188  * @pages:	array that receives pointer to the page pinned.
189  *		Must be at least nr_segs long.
190  *
191  * Returns 1 if page is pinned. If the page was not pinned, returns
192  * -errno. The page returned must be released with a put_page() call
193  * when it is finished with.
194  */
195 int get_kernel_page(unsigned long start, int write, struct page **pages)
196 {
197 	const struct kvec kiov = {
198 		.iov_base = (void *)start,
199 		.iov_len = PAGE_SIZE
200 	};
201 
202 	return get_kernel_pages(&kiov, 1, write, pages);
203 }
204 EXPORT_SYMBOL_GPL(get_kernel_page);
205 
206 static void pagevec_lru_move_fn(struct pagevec *pvec,
207 	void (*move_fn)(struct page *page, struct lruvec *lruvec, void *arg),
208 	void *arg)
209 {
210 	int i;
211 	struct pglist_data *pgdat = NULL;
212 	struct lruvec *lruvec;
213 	unsigned long flags = 0;
214 
215 	for (i = 0; i < pagevec_count(pvec); i++) {
216 		struct page *page = pvec->pages[i];
217 		struct pglist_data *pagepgdat = page_pgdat(page);
218 
219 		if (pagepgdat != pgdat) {
220 			if (pgdat)
221 				spin_unlock_irqrestore(&pgdat->lru_lock, flags);
222 			pgdat = pagepgdat;
223 			spin_lock_irqsave(&pgdat->lru_lock, flags);
224 		}
225 
226 		lruvec = mem_cgroup_page_lruvec(page, pgdat);
227 		(*move_fn)(page, lruvec, arg);
228 	}
229 	if (pgdat)
230 		spin_unlock_irqrestore(&pgdat->lru_lock, flags);
231 	release_pages(pvec->pages, pvec->nr);
232 	pagevec_reinit(pvec);
233 }
234 
235 static void pagevec_move_tail_fn(struct page *page, struct lruvec *lruvec,
236 				 void *arg)
237 {
238 	int *pgmoved = arg;
239 
240 	if (PageLRU(page) && !PageUnevictable(page)) {
241 		del_page_from_lru_list(page, lruvec, page_lru(page));
242 		ClearPageActive(page);
243 		add_page_to_lru_list_tail(page, lruvec, page_lru(page));
244 		(*pgmoved) += thp_nr_pages(page);
245 	}
246 }
247 
248 /*
249  * pagevec_move_tail() must be called with IRQ disabled.
250  * Otherwise this may cause nasty races.
251  */
252 static void pagevec_move_tail(struct pagevec *pvec)
253 {
254 	int pgmoved = 0;
255 
256 	pagevec_lru_move_fn(pvec, pagevec_move_tail_fn, &pgmoved);
257 	__count_vm_events(PGROTATED, pgmoved);
258 }
259 
260 /*
261  * Writeback is about to end against a page which has been marked for immediate
262  * reclaim.  If it still appears to be reclaimable, move it to the tail of the
263  * inactive list.
264  */
265 void rotate_reclaimable_page(struct page *page)
266 {
267 	if (!PageLocked(page) && !PageDirty(page) &&
268 	    !PageUnevictable(page) && PageLRU(page)) {
269 		struct pagevec *pvec;
270 		unsigned long flags;
271 
272 		get_page(page);
273 		local_lock_irqsave(&lru_rotate.lock, flags);
274 		pvec = this_cpu_ptr(&lru_rotate.pvec);
275 		if (!pagevec_add(pvec, page) || PageCompound(page))
276 			pagevec_move_tail(pvec);
277 		local_unlock_irqrestore(&lru_rotate.lock, flags);
278 	}
279 }
280 
281 void lru_note_cost(struct lruvec *lruvec, bool file, unsigned int nr_pages)
282 {
283 	do {
284 		unsigned long lrusize;
285 
286 		/* Record cost event */
287 		if (file)
288 			lruvec->file_cost += nr_pages;
289 		else
290 			lruvec->anon_cost += nr_pages;
291 
292 		/*
293 		 * Decay previous events
294 		 *
295 		 * Because workloads change over time (and to avoid
296 		 * overflow) we keep these statistics as a floating
297 		 * average, which ends up weighing recent refaults
298 		 * more than old ones.
299 		 */
300 		lrusize = lruvec_page_state(lruvec, NR_INACTIVE_ANON) +
301 			  lruvec_page_state(lruvec, NR_ACTIVE_ANON) +
302 			  lruvec_page_state(lruvec, NR_INACTIVE_FILE) +
303 			  lruvec_page_state(lruvec, NR_ACTIVE_FILE);
304 
305 		if (lruvec->file_cost + lruvec->anon_cost > lrusize / 4) {
306 			lruvec->file_cost /= 2;
307 			lruvec->anon_cost /= 2;
308 		}
309 	} while ((lruvec = parent_lruvec(lruvec)));
310 }
311 
312 void lru_note_cost_page(struct page *page)
313 {
314 	lru_note_cost(mem_cgroup_page_lruvec(page, page_pgdat(page)),
315 		      page_is_file_lru(page), thp_nr_pages(page));
316 }
317 
318 static void __activate_page(struct page *page, struct lruvec *lruvec,
319 			    void *arg)
320 {
321 	if (PageLRU(page) && !PageActive(page) && !PageUnevictable(page)) {
322 		int lru = page_lru_base_type(page);
323 		int nr_pages = thp_nr_pages(page);
324 
325 		del_page_from_lru_list(page, lruvec, lru);
326 		SetPageActive(page);
327 		lru += LRU_ACTIVE;
328 		add_page_to_lru_list(page, lruvec, lru);
329 		trace_mm_lru_activate(page);
330 
331 		__count_vm_events(PGACTIVATE, nr_pages);
332 		__count_memcg_events(lruvec_memcg(lruvec), PGACTIVATE,
333 				     nr_pages);
334 	}
335 }
336 
337 #ifdef CONFIG_SMP
338 static void activate_page_drain(int cpu)
339 {
340 	struct pagevec *pvec = &per_cpu(lru_pvecs.activate_page, cpu);
341 
342 	if (pagevec_count(pvec))
343 		pagevec_lru_move_fn(pvec, __activate_page, NULL);
344 }
345 
346 static bool need_activate_page_drain(int cpu)
347 {
348 	return pagevec_count(&per_cpu(lru_pvecs.activate_page, cpu)) != 0;
349 }
350 
351 void activate_page(struct page *page)
352 {
353 	page = compound_head(page);
354 	if (PageLRU(page) && !PageActive(page) && !PageUnevictable(page)) {
355 		struct pagevec *pvec;
356 
357 		local_lock(&lru_pvecs.lock);
358 		pvec = this_cpu_ptr(&lru_pvecs.activate_page);
359 		get_page(page);
360 		if (!pagevec_add(pvec, page) || PageCompound(page))
361 			pagevec_lru_move_fn(pvec, __activate_page, NULL);
362 		local_unlock(&lru_pvecs.lock);
363 	}
364 }
365 
366 #else
367 static inline void activate_page_drain(int cpu)
368 {
369 }
370 
371 void activate_page(struct page *page)
372 {
373 	pg_data_t *pgdat = page_pgdat(page);
374 
375 	page = compound_head(page);
376 	spin_lock_irq(&pgdat->lru_lock);
377 	__activate_page(page, mem_cgroup_page_lruvec(page, pgdat), NULL);
378 	spin_unlock_irq(&pgdat->lru_lock);
379 }
380 #endif
381 
382 static void __lru_cache_activate_page(struct page *page)
383 {
384 	struct pagevec *pvec;
385 	int i;
386 
387 	local_lock(&lru_pvecs.lock);
388 	pvec = this_cpu_ptr(&lru_pvecs.lru_add);
389 
390 	/*
391 	 * Search backwards on the optimistic assumption that the page being
392 	 * activated has just been added to this pagevec. Note that only
393 	 * the local pagevec is examined as a !PageLRU page could be in the
394 	 * process of being released, reclaimed, migrated or on a remote
395 	 * pagevec that is currently being drained. Furthermore, marking
396 	 * a remote pagevec's page PageActive potentially hits a race where
397 	 * a page is marked PageActive just after it is added to the inactive
398 	 * list causing accounting errors and BUG_ON checks to trigger.
399 	 */
400 	for (i = pagevec_count(pvec) - 1; i >= 0; i--) {
401 		struct page *pagevec_page = pvec->pages[i];
402 
403 		if (pagevec_page == page) {
404 			SetPageActive(page);
405 			break;
406 		}
407 	}
408 
409 	local_unlock(&lru_pvecs.lock);
410 }
411 
412 /*
413  * Mark a page as having seen activity.
414  *
415  * inactive,unreferenced	->	inactive,referenced
416  * inactive,referenced		->	active,unreferenced
417  * active,unreferenced		->	active,referenced
418  *
419  * When a newly allocated page is not yet visible, so safe for non-atomic ops,
420  * __SetPageReferenced(page) may be substituted for mark_page_accessed(page).
421  */
422 void mark_page_accessed(struct page *page)
423 {
424 	page = compound_head(page);
425 
426 	if (!PageReferenced(page)) {
427 		SetPageReferenced(page);
428 	} else if (PageUnevictable(page)) {
429 		/*
430 		 * Unevictable pages are on the "LRU_UNEVICTABLE" list. But,
431 		 * this list is never rotated or maintained, so marking an
432 		 * evictable page accessed has no effect.
433 		 */
434 	} else if (!PageActive(page)) {
435 		/*
436 		 * If the page is on the LRU, queue it for activation via
437 		 * lru_pvecs.activate_page. Otherwise, assume the page is on a
438 		 * pagevec, mark it active and it'll be moved to the active
439 		 * LRU on the next drain.
440 		 */
441 		if (PageLRU(page))
442 			activate_page(page);
443 		else
444 			__lru_cache_activate_page(page);
445 		ClearPageReferenced(page);
446 		workingset_activation(page);
447 	}
448 	if (page_is_idle(page))
449 		clear_page_idle(page);
450 }
451 EXPORT_SYMBOL(mark_page_accessed);
452 
453 /**
454  * lru_cache_add - add a page to a page list
455  * @page: the page to be added to the LRU.
456  *
457  * Queue the page for addition to the LRU via pagevec. The decision on whether
458  * to add the page to the [in]active [file|anon] list is deferred until the
459  * pagevec is drained. This gives a chance for the caller of lru_cache_add()
460  * have the page added to the active list using mark_page_accessed().
461  */
462 void lru_cache_add(struct page *page)
463 {
464 	struct pagevec *pvec;
465 
466 	VM_BUG_ON_PAGE(PageActive(page) && PageUnevictable(page), page);
467 	VM_BUG_ON_PAGE(PageLRU(page), page);
468 
469 	get_page(page);
470 	local_lock(&lru_pvecs.lock);
471 	pvec = this_cpu_ptr(&lru_pvecs.lru_add);
472 	if (!pagevec_add(pvec, page) || PageCompound(page))
473 		__pagevec_lru_add(pvec);
474 	local_unlock(&lru_pvecs.lock);
475 }
476 EXPORT_SYMBOL(lru_cache_add);
477 
478 /**
479  * lru_cache_add_inactive_or_unevictable
480  * @page:  the page to be added to LRU
481  * @vma:   vma in which page is mapped for determining reclaimability
482  *
483  * Place @page on the inactive or unevictable LRU list, depending on its
484  * evictability.  Note that if the page is not evictable, it goes
485  * directly back onto it's zone's unevictable list, it does NOT use a
486  * per cpu pagevec.
487  */
488 void lru_cache_add_inactive_or_unevictable(struct page *page,
489 					 struct vm_area_struct *vma)
490 {
491 	bool unevictable;
492 
493 	VM_BUG_ON_PAGE(PageLRU(page), page);
494 
495 	unevictable = (vma->vm_flags & (VM_LOCKED | VM_SPECIAL)) == VM_LOCKED;
496 	if (unlikely(unevictable) && !TestSetPageMlocked(page)) {
497 		int nr_pages = thp_nr_pages(page);
498 		/*
499 		 * We use the irq-unsafe __mod_zone_page_stat because this
500 		 * counter is not modified from interrupt context, and the pte
501 		 * lock is held(spinlock), which implies preemption disabled.
502 		 */
503 		__mod_zone_page_state(page_zone(page), NR_MLOCK, nr_pages);
504 		count_vm_events(UNEVICTABLE_PGMLOCKED, nr_pages);
505 	}
506 	lru_cache_add(page);
507 }
508 
509 /*
510  * If the page can not be invalidated, it is moved to the
511  * inactive list to speed up its reclaim.  It is moved to the
512  * head of the list, rather than the tail, to give the flusher
513  * threads some time to write it out, as this is much more
514  * effective than the single-page writeout from reclaim.
515  *
516  * If the page isn't page_mapped and dirty/writeback, the page
517  * could reclaim asap using PG_reclaim.
518  *
519  * 1. active, mapped page -> none
520  * 2. active, dirty/writeback page -> inactive, head, PG_reclaim
521  * 3. inactive, mapped page -> none
522  * 4. inactive, dirty/writeback page -> inactive, head, PG_reclaim
523  * 5. inactive, clean -> inactive, tail
524  * 6. Others -> none
525  *
526  * In 4, why it moves inactive's head, the VM expects the page would
527  * be write it out by flusher threads as this is much more effective
528  * than the single-page writeout from reclaim.
529  */
530 static void lru_deactivate_file_fn(struct page *page, struct lruvec *lruvec,
531 			      void *arg)
532 {
533 	int lru;
534 	bool active;
535 	int nr_pages = thp_nr_pages(page);
536 
537 	if (!PageLRU(page))
538 		return;
539 
540 	if (PageUnevictable(page))
541 		return;
542 
543 	/* Some processes are using the page */
544 	if (page_mapped(page))
545 		return;
546 
547 	active = PageActive(page);
548 	lru = page_lru_base_type(page);
549 
550 	del_page_from_lru_list(page, lruvec, lru + active);
551 	ClearPageActive(page);
552 	ClearPageReferenced(page);
553 
554 	if (PageWriteback(page) || PageDirty(page)) {
555 		/*
556 		 * PG_reclaim could be raced with end_page_writeback
557 		 * It can make readahead confusing.  But race window
558 		 * is _really_ small and  it's non-critical problem.
559 		 */
560 		add_page_to_lru_list(page, lruvec, lru);
561 		SetPageReclaim(page);
562 	} else {
563 		/*
564 		 * The page's writeback ends up during pagevec
565 		 * We moves tha page into tail of inactive.
566 		 */
567 		add_page_to_lru_list_tail(page, lruvec, lru);
568 		__count_vm_events(PGROTATED, nr_pages);
569 	}
570 
571 	if (active) {
572 		__count_vm_events(PGDEACTIVATE, nr_pages);
573 		__count_memcg_events(lruvec_memcg(lruvec), PGDEACTIVATE,
574 				     nr_pages);
575 	}
576 }
577 
578 static void lru_deactivate_fn(struct page *page, struct lruvec *lruvec,
579 			    void *arg)
580 {
581 	if (PageLRU(page) && PageActive(page) && !PageUnevictable(page)) {
582 		int lru = page_lru_base_type(page);
583 		int nr_pages = thp_nr_pages(page);
584 
585 		del_page_from_lru_list(page, lruvec, lru + LRU_ACTIVE);
586 		ClearPageActive(page);
587 		ClearPageReferenced(page);
588 		add_page_to_lru_list(page, lruvec, lru);
589 
590 		__count_vm_events(PGDEACTIVATE, nr_pages);
591 		__count_memcg_events(lruvec_memcg(lruvec), PGDEACTIVATE,
592 				     nr_pages);
593 	}
594 }
595 
596 static void lru_lazyfree_fn(struct page *page, struct lruvec *lruvec,
597 			    void *arg)
598 {
599 	if (PageLRU(page) && PageAnon(page) && PageSwapBacked(page) &&
600 	    !PageSwapCache(page) && !PageUnevictable(page)) {
601 		bool active = PageActive(page);
602 		int nr_pages = thp_nr_pages(page);
603 
604 		del_page_from_lru_list(page, lruvec,
605 				       LRU_INACTIVE_ANON + active);
606 		ClearPageActive(page);
607 		ClearPageReferenced(page);
608 		/*
609 		 * Lazyfree pages are clean anonymous pages.  They have
610 		 * PG_swapbacked flag cleared, to distinguish them from normal
611 		 * anonymous pages
612 		 */
613 		ClearPageSwapBacked(page);
614 		add_page_to_lru_list(page, lruvec, LRU_INACTIVE_FILE);
615 
616 		__count_vm_events(PGLAZYFREE, nr_pages);
617 		__count_memcg_events(lruvec_memcg(lruvec), PGLAZYFREE,
618 				     nr_pages);
619 	}
620 }
621 
622 /*
623  * Drain pages out of the cpu's pagevecs.
624  * Either "cpu" is the current CPU, and preemption has already been
625  * disabled; or "cpu" is being hot-unplugged, and is already dead.
626  */
627 void lru_add_drain_cpu(int cpu)
628 {
629 	struct pagevec *pvec = &per_cpu(lru_pvecs.lru_add, cpu);
630 
631 	if (pagevec_count(pvec))
632 		__pagevec_lru_add(pvec);
633 
634 	pvec = &per_cpu(lru_rotate.pvec, cpu);
635 	/* Disabling interrupts below acts as a compiler barrier. */
636 	if (data_race(pagevec_count(pvec))) {
637 		unsigned long flags;
638 
639 		/* No harm done if a racing interrupt already did this */
640 		local_lock_irqsave(&lru_rotate.lock, flags);
641 		pagevec_move_tail(pvec);
642 		local_unlock_irqrestore(&lru_rotate.lock, flags);
643 	}
644 
645 	pvec = &per_cpu(lru_pvecs.lru_deactivate_file, cpu);
646 	if (pagevec_count(pvec))
647 		pagevec_lru_move_fn(pvec, lru_deactivate_file_fn, NULL);
648 
649 	pvec = &per_cpu(lru_pvecs.lru_deactivate, cpu);
650 	if (pagevec_count(pvec))
651 		pagevec_lru_move_fn(pvec, lru_deactivate_fn, NULL);
652 
653 	pvec = &per_cpu(lru_pvecs.lru_lazyfree, cpu);
654 	if (pagevec_count(pvec))
655 		pagevec_lru_move_fn(pvec, lru_lazyfree_fn, NULL);
656 
657 	activate_page_drain(cpu);
658 }
659 
660 /**
661  * deactivate_file_page - forcefully deactivate a file page
662  * @page: page to deactivate
663  *
664  * This function hints the VM that @page is a good reclaim candidate,
665  * for example if its invalidation fails due to the page being dirty
666  * or under writeback.
667  */
668 void deactivate_file_page(struct page *page)
669 {
670 	/*
671 	 * In a workload with many unevictable page such as mprotect,
672 	 * unevictable page deactivation for accelerating reclaim is pointless.
673 	 */
674 	if (PageUnevictable(page))
675 		return;
676 
677 	if (likely(get_page_unless_zero(page))) {
678 		struct pagevec *pvec;
679 
680 		local_lock(&lru_pvecs.lock);
681 		pvec = this_cpu_ptr(&lru_pvecs.lru_deactivate_file);
682 
683 		if (!pagevec_add(pvec, page) || PageCompound(page))
684 			pagevec_lru_move_fn(pvec, lru_deactivate_file_fn, NULL);
685 		local_unlock(&lru_pvecs.lock);
686 	}
687 }
688 
689 /*
690  * deactivate_page - deactivate a page
691  * @page: page to deactivate
692  *
693  * deactivate_page() moves @page to the inactive list if @page was on the active
694  * list and was not an unevictable page.  This is done to accelerate the reclaim
695  * of @page.
696  */
697 void deactivate_page(struct page *page)
698 {
699 	if (PageLRU(page) && PageActive(page) && !PageUnevictable(page)) {
700 		struct pagevec *pvec;
701 
702 		local_lock(&lru_pvecs.lock);
703 		pvec = this_cpu_ptr(&lru_pvecs.lru_deactivate);
704 		get_page(page);
705 		if (!pagevec_add(pvec, page) || PageCompound(page))
706 			pagevec_lru_move_fn(pvec, lru_deactivate_fn, NULL);
707 		local_unlock(&lru_pvecs.lock);
708 	}
709 }
710 
711 /**
712  * mark_page_lazyfree - make an anon page lazyfree
713  * @page: page to deactivate
714  *
715  * mark_page_lazyfree() moves @page to the inactive file list.
716  * This is done to accelerate the reclaim of @page.
717  */
718 void mark_page_lazyfree(struct page *page)
719 {
720 	if (PageLRU(page) && PageAnon(page) && PageSwapBacked(page) &&
721 	    !PageSwapCache(page) && !PageUnevictable(page)) {
722 		struct pagevec *pvec;
723 
724 		local_lock(&lru_pvecs.lock);
725 		pvec = this_cpu_ptr(&lru_pvecs.lru_lazyfree);
726 		get_page(page);
727 		if (!pagevec_add(pvec, page) || PageCompound(page))
728 			pagevec_lru_move_fn(pvec, lru_lazyfree_fn, NULL);
729 		local_unlock(&lru_pvecs.lock);
730 	}
731 }
732 
733 void lru_add_drain(void)
734 {
735 	local_lock(&lru_pvecs.lock);
736 	lru_add_drain_cpu(smp_processor_id());
737 	local_unlock(&lru_pvecs.lock);
738 }
739 
740 void lru_add_drain_cpu_zone(struct zone *zone)
741 {
742 	local_lock(&lru_pvecs.lock);
743 	lru_add_drain_cpu(smp_processor_id());
744 	drain_local_pages(zone);
745 	local_unlock(&lru_pvecs.lock);
746 }
747 
748 #ifdef CONFIG_SMP
749 
750 static DEFINE_PER_CPU(struct work_struct, lru_add_drain_work);
751 
752 static void lru_add_drain_per_cpu(struct work_struct *dummy)
753 {
754 	lru_add_drain();
755 }
756 
757 /*
758  * Doesn't need any cpu hotplug locking because we do rely on per-cpu
759  * kworkers being shut down before our page_alloc_cpu_dead callback is
760  * executed on the offlined cpu.
761  * Calling this function with cpu hotplug locks held can actually lead
762  * to obscure indirect dependencies via WQ context.
763  */
764 void lru_add_drain_all(void)
765 {
766 	static seqcount_t seqcount = SEQCNT_ZERO(seqcount);
767 	static DEFINE_MUTEX(lock);
768 	static struct cpumask has_work;
769 	int cpu, seq;
770 
771 	/*
772 	 * Make sure nobody triggers this path before mm_percpu_wq is fully
773 	 * initialized.
774 	 */
775 	if (WARN_ON(!mm_percpu_wq))
776 		return;
777 
778 	seq = raw_read_seqcount_latch(&seqcount);
779 
780 	mutex_lock(&lock);
781 
782 	/*
783 	 * Piggyback on drain started and finished while we waited for lock:
784 	 * all pages pended at the time of our enter were drained from vectors.
785 	 */
786 	if (__read_seqcount_retry(&seqcount, seq))
787 		goto done;
788 
789 	raw_write_seqcount_latch(&seqcount);
790 
791 	cpumask_clear(&has_work);
792 
793 	for_each_online_cpu(cpu) {
794 		struct work_struct *work = &per_cpu(lru_add_drain_work, cpu);
795 
796 		if (pagevec_count(&per_cpu(lru_pvecs.lru_add, cpu)) ||
797 		    data_race(pagevec_count(&per_cpu(lru_rotate.pvec, cpu))) ||
798 		    pagevec_count(&per_cpu(lru_pvecs.lru_deactivate_file, cpu)) ||
799 		    pagevec_count(&per_cpu(lru_pvecs.lru_deactivate, cpu)) ||
800 		    pagevec_count(&per_cpu(lru_pvecs.lru_lazyfree, cpu)) ||
801 		    need_activate_page_drain(cpu)) {
802 			INIT_WORK(work, lru_add_drain_per_cpu);
803 			queue_work_on(cpu, mm_percpu_wq, work);
804 			cpumask_set_cpu(cpu, &has_work);
805 		}
806 	}
807 
808 	for_each_cpu(cpu, &has_work)
809 		flush_work(&per_cpu(lru_add_drain_work, cpu));
810 
811 done:
812 	mutex_unlock(&lock);
813 }
814 #else
815 void lru_add_drain_all(void)
816 {
817 	lru_add_drain();
818 }
819 #endif
820 
821 /**
822  * release_pages - batched put_page()
823  * @pages: array of pages to release
824  * @nr: number of pages
825  *
826  * Decrement the reference count on all the pages in @pages.  If it
827  * fell to zero, remove the page from the LRU and free it.
828  */
829 void release_pages(struct page **pages, int nr)
830 {
831 	int i;
832 	LIST_HEAD(pages_to_free);
833 	struct pglist_data *locked_pgdat = NULL;
834 	struct lruvec *lruvec;
835 	unsigned long flags;
836 	unsigned int lock_batch;
837 
838 	for (i = 0; i < nr; i++) {
839 		struct page *page = pages[i];
840 
841 		/*
842 		 * Make sure the IRQ-safe lock-holding time does not get
843 		 * excessive with a continuous string of pages from the
844 		 * same pgdat. The lock is held only if pgdat != NULL.
845 		 */
846 		if (locked_pgdat && ++lock_batch == SWAP_CLUSTER_MAX) {
847 			spin_unlock_irqrestore(&locked_pgdat->lru_lock, flags);
848 			locked_pgdat = NULL;
849 		}
850 
851 		if (is_huge_zero_page(page))
852 			continue;
853 
854 		if (is_zone_device_page(page)) {
855 			if (locked_pgdat) {
856 				spin_unlock_irqrestore(&locked_pgdat->lru_lock,
857 						       flags);
858 				locked_pgdat = NULL;
859 			}
860 			/*
861 			 * ZONE_DEVICE pages that return 'false' from
862 			 * put_devmap_managed_page() do not require special
863 			 * processing, and instead, expect a call to
864 			 * put_page_testzero().
865 			 */
866 			if (page_is_devmap_managed(page)) {
867 				put_devmap_managed_page(page);
868 				continue;
869 			}
870 		}
871 
872 		page = compound_head(page);
873 		if (!put_page_testzero(page))
874 			continue;
875 
876 		if (PageCompound(page)) {
877 			if (locked_pgdat) {
878 				spin_unlock_irqrestore(&locked_pgdat->lru_lock, flags);
879 				locked_pgdat = NULL;
880 			}
881 			__put_compound_page(page);
882 			continue;
883 		}
884 
885 		if (PageLRU(page)) {
886 			struct pglist_data *pgdat = page_pgdat(page);
887 
888 			if (pgdat != locked_pgdat) {
889 				if (locked_pgdat)
890 					spin_unlock_irqrestore(&locked_pgdat->lru_lock,
891 									flags);
892 				lock_batch = 0;
893 				locked_pgdat = pgdat;
894 				spin_lock_irqsave(&locked_pgdat->lru_lock, flags);
895 			}
896 
897 			lruvec = mem_cgroup_page_lruvec(page, locked_pgdat);
898 			VM_BUG_ON_PAGE(!PageLRU(page), page);
899 			__ClearPageLRU(page);
900 			del_page_from_lru_list(page, lruvec, page_off_lru(page));
901 		}
902 
903 		/* Clear Active bit in case of parallel mark_page_accessed */
904 		__ClearPageActive(page);
905 		__ClearPageWaiters(page);
906 
907 		list_add(&page->lru, &pages_to_free);
908 	}
909 	if (locked_pgdat)
910 		spin_unlock_irqrestore(&locked_pgdat->lru_lock, flags);
911 
912 	mem_cgroup_uncharge_list(&pages_to_free);
913 	free_unref_page_list(&pages_to_free);
914 }
915 EXPORT_SYMBOL(release_pages);
916 
917 /*
918  * The pages which we're about to release may be in the deferred lru-addition
919  * queues.  That would prevent them from really being freed right now.  That's
920  * OK from a correctness point of view but is inefficient - those pages may be
921  * cache-warm and we want to give them back to the page allocator ASAP.
922  *
923  * So __pagevec_release() will drain those queues here.  __pagevec_lru_add()
924  * and __pagevec_lru_add_active() call release_pages() directly to avoid
925  * mutual recursion.
926  */
927 void __pagevec_release(struct pagevec *pvec)
928 {
929 	if (!pvec->percpu_pvec_drained) {
930 		lru_add_drain();
931 		pvec->percpu_pvec_drained = true;
932 	}
933 	release_pages(pvec->pages, pagevec_count(pvec));
934 	pagevec_reinit(pvec);
935 }
936 EXPORT_SYMBOL(__pagevec_release);
937 
938 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
939 /* used by __split_huge_page_refcount() */
940 void lru_add_page_tail(struct page *page, struct page *page_tail,
941 		       struct lruvec *lruvec, struct list_head *list)
942 {
943 	VM_BUG_ON_PAGE(!PageHead(page), page);
944 	VM_BUG_ON_PAGE(PageCompound(page_tail), page);
945 	VM_BUG_ON_PAGE(PageLRU(page_tail), page);
946 	lockdep_assert_held(&lruvec_pgdat(lruvec)->lru_lock);
947 
948 	if (!list)
949 		SetPageLRU(page_tail);
950 
951 	if (likely(PageLRU(page)))
952 		list_add_tail(&page_tail->lru, &page->lru);
953 	else if (list) {
954 		/* page reclaim is reclaiming a huge page */
955 		get_page(page_tail);
956 		list_add_tail(&page_tail->lru, list);
957 	} else {
958 		/*
959 		 * Head page has not yet been counted, as an hpage,
960 		 * so we must account for each subpage individually.
961 		 *
962 		 * Put page_tail on the list at the correct position
963 		 * so they all end up in order.
964 		 */
965 		add_page_to_lru_list_tail(page_tail, lruvec,
966 					  page_lru(page_tail));
967 	}
968 }
969 #endif /* CONFIG_TRANSPARENT_HUGEPAGE */
970 
971 static void __pagevec_lru_add_fn(struct page *page, struct lruvec *lruvec,
972 				 void *arg)
973 {
974 	enum lru_list lru;
975 	int was_unevictable = TestClearPageUnevictable(page);
976 	int nr_pages = thp_nr_pages(page);
977 
978 	VM_BUG_ON_PAGE(PageLRU(page), page);
979 
980 	/*
981 	 * Page becomes evictable in two ways:
982 	 * 1) Within LRU lock [munlock_vma_page() and __munlock_pagevec()].
983 	 * 2) Before acquiring LRU lock to put the page to correct LRU and then
984 	 *   a) do PageLRU check with lock [check_move_unevictable_pages]
985 	 *   b) do PageLRU check before lock [clear_page_mlock]
986 	 *
987 	 * (1) & (2a) are ok as LRU lock will serialize them. For (2b), we need
988 	 * following strict ordering:
989 	 *
990 	 * #0: __pagevec_lru_add_fn		#1: clear_page_mlock
991 	 *
992 	 * SetPageLRU()				TestClearPageMlocked()
993 	 * smp_mb() // explicit ordering	// above provides strict
994 	 *					// ordering
995 	 * PageMlocked()			PageLRU()
996 	 *
997 	 *
998 	 * if '#1' does not observe setting of PG_lru by '#0' and fails
999 	 * isolation, the explicit barrier will make sure that page_evictable
1000 	 * check will put the page in correct LRU. Without smp_mb(), SetPageLRU
1001 	 * can be reordered after PageMlocked check and can make '#1' to fail
1002 	 * the isolation of the page whose Mlocked bit is cleared (#0 is also
1003 	 * looking at the same page) and the evictable page will be stranded
1004 	 * in an unevictable LRU.
1005 	 */
1006 	SetPageLRU(page);
1007 	smp_mb__after_atomic();
1008 
1009 	if (page_evictable(page)) {
1010 		lru = page_lru(page);
1011 		if (was_unevictable)
1012 			__count_vm_events(UNEVICTABLE_PGRESCUED, nr_pages);
1013 	} else {
1014 		lru = LRU_UNEVICTABLE;
1015 		ClearPageActive(page);
1016 		SetPageUnevictable(page);
1017 		if (!was_unevictable)
1018 			__count_vm_events(UNEVICTABLE_PGCULLED, nr_pages);
1019 	}
1020 
1021 	add_page_to_lru_list(page, lruvec, lru);
1022 	trace_mm_lru_insertion(page, lru);
1023 }
1024 
1025 /*
1026  * Add the passed pages to the LRU, then drop the caller's refcount
1027  * on them.  Reinitialises the caller's pagevec.
1028  */
1029 void __pagevec_lru_add(struct pagevec *pvec)
1030 {
1031 	pagevec_lru_move_fn(pvec, __pagevec_lru_add_fn, NULL);
1032 }
1033 
1034 /**
1035  * pagevec_lookup_entries - gang pagecache lookup
1036  * @pvec:	Where the resulting entries are placed
1037  * @mapping:	The address_space to search
1038  * @start:	The starting entry index
1039  * @nr_entries:	The maximum number of pages
1040  * @indices:	The cache indices corresponding to the entries in @pvec
1041  *
1042  * pagevec_lookup_entries() will search for and return a group of up
1043  * to @nr_pages pages and shadow entries in the mapping.  All
1044  * entries are placed in @pvec.  pagevec_lookup_entries() takes a
1045  * reference against actual pages in @pvec.
1046  *
1047  * The search returns a group of mapping-contiguous entries with
1048  * ascending indexes.  There may be holes in the indices due to
1049  * not-present entries.
1050  *
1051  * Only one subpage of a Transparent Huge Page is returned in one call:
1052  * allowing truncate_inode_pages_range() to evict the whole THP without
1053  * cycling through a pagevec of extra references.
1054  *
1055  * pagevec_lookup_entries() returns the number of entries which were
1056  * found.
1057  */
1058 unsigned pagevec_lookup_entries(struct pagevec *pvec,
1059 				struct address_space *mapping,
1060 				pgoff_t start, unsigned nr_entries,
1061 				pgoff_t *indices)
1062 {
1063 	pvec->nr = find_get_entries(mapping, start, nr_entries,
1064 				    pvec->pages, indices);
1065 	return pagevec_count(pvec);
1066 }
1067 
1068 /**
1069  * pagevec_remove_exceptionals - pagevec exceptionals pruning
1070  * @pvec:	The pagevec to prune
1071  *
1072  * pagevec_lookup_entries() fills both pages and exceptional radix
1073  * tree entries into the pagevec.  This function prunes all
1074  * exceptionals from @pvec without leaving holes, so that it can be
1075  * passed on to page-only pagevec operations.
1076  */
1077 void pagevec_remove_exceptionals(struct pagevec *pvec)
1078 {
1079 	int i, j;
1080 
1081 	for (i = 0, j = 0; i < pagevec_count(pvec); i++) {
1082 		struct page *page = pvec->pages[i];
1083 		if (!xa_is_value(page))
1084 			pvec->pages[j++] = page;
1085 	}
1086 	pvec->nr = j;
1087 }
1088 
1089 /**
1090  * pagevec_lookup_range - gang pagecache lookup
1091  * @pvec:	Where the resulting pages are placed
1092  * @mapping:	The address_space to search
1093  * @start:	The starting page index
1094  * @end:	The final page index
1095  *
1096  * pagevec_lookup_range() will search for & return a group of up to PAGEVEC_SIZE
1097  * pages in the mapping starting from index @start and upto index @end
1098  * (inclusive).  The pages are placed in @pvec.  pagevec_lookup() takes a
1099  * reference against the pages in @pvec.
1100  *
1101  * The search returns a group of mapping-contiguous pages with ascending
1102  * indexes.  There may be holes in the indices due to not-present pages. We
1103  * also update @start to index the next page for the traversal.
1104  *
1105  * pagevec_lookup_range() returns the number of pages which were found. If this
1106  * number is smaller than PAGEVEC_SIZE, the end of specified range has been
1107  * reached.
1108  */
1109 unsigned pagevec_lookup_range(struct pagevec *pvec,
1110 		struct address_space *mapping, pgoff_t *start, pgoff_t end)
1111 {
1112 	pvec->nr = find_get_pages_range(mapping, start, end, PAGEVEC_SIZE,
1113 					pvec->pages);
1114 	return pagevec_count(pvec);
1115 }
1116 EXPORT_SYMBOL(pagevec_lookup_range);
1117 
1118 unsigned pagevec_lookup_range_tag(struct pagevec *pvec,
1119 		struct address_space *mapping, pgoff_t *index, pgoff_t end,
1120 		xa_mark_t tag)
1121 {
1122 	pvec->nr = find_get_pages_range_tag(mapping, index, end, tag,
1123 					PAGEVEC_SIZE, pvec->pages);
1124 	return pagevec_count(pvec);
1125 }
1126 EXPORT_SYMBOL(pagevec_lookup_range_tag);
1127 
1128 unsigned pagevec_lookup_range_nr_tag(struct pagevec *pvec,
1129 		struct address_space *mapping, pgoff_t *index, pgoff_t end,
1130 		xa_mark_t tag, unsigned max_pages)
1131 {
1132 	pvec->nr = find_get_pages_range_tag(mapping, index, end, tag,
1133 		min_t(unsigned int, max_pages, PAGEVEC_SIZE), pvec->pages);
1134 	return pagevec_count(pvec);
1135 }
1136 EXPORT_SYMBOL(pagevec_lookup_range_nr_tag);
1137 /*
1138  * Perform any setup for the swap system
1139  */
1140 void __init swap_setup(void)
1141 {
1142 	unsigned long megs = totalram_pages() >> (20 - PAGE_SHIFT);
1143 
1144 	/* Use a smaller cluster for small-memory machines */
1145 	if (megs < 16)
1146 		page_cluster = 2;
1147 	else
1148 		page_cluster = 3;
1149 	/*
1150 	 * Right now other parts of the system means that we
1151 	 * _really_ don't want to cluster much more
1152 	 */
1153 }
1154 
1155 #ifdef CONFIG_DEV_PAGEMAP_OPS
1156 void put_devmap_managed_page(struct page *page)
1157 {
1158 	int count;
1159 
1160 	if (WARN_ON_ONCE(!page_is_devmap_managed(page)))
1161 		return;
1162 
1163 	count = page_ref_dec_return(page);
1164 
1165 	/*
1166 	 * devmap page refcounts are 1-based, rather than 0-based: if
1167 	 * refcount is 1, then the page is free and the refcount is
1168 	 * stable because nobody holds a reference on the page.
1169 	 */
1170 	if (count == 1)
1171 		free_devmap_managed_page(page);
1172 	else if (!count)
1173 		__put_page(page);
1174 }
1175 EXPORT_SYMBOL(put_devmap_managed_page);
1176 #endif
1177