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v3.1
 
  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 operation 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/percpu_counter.h>
 
 28#include <linux/percpu.h>
 29#include <linux/cpu.h>
 30#include <linux/notifier.h>
 31#include <linux/backing-dev.h>
 32#include <linux/memcontrol.h>
 33#include <linux/gfp.h>
 
 
 
 
 
 34
 35#include "internal.h"
 36
 37/* How many pages do we try to swap or page in/out together? */
 
 
 
 38int page_cluster;
 
 39
 40static DEFINE_PER_CPU(struct pagevec[NR_LRU_LISTS], lru_add_pvecs);
 41static DEFINE_PER_CPU(struct pagevec, lru_rotate_pvecs);
 42static DEFINE_PER_CPU(struct pagevec, lru_deactivate_pvecs);
 
 
 
 
 
 43
 44/*
 45 * This path almost never happens for VM activity - pages are normally
 46 * freed via pagevecs.  But it gets used by networking.
 47 */
 48static void __page_cache_release(struct page *page)
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 49{
 50	if (PageLRU(page)) {
 
 51		unsigned long flags;
 52		struct zone *zone = page_zone(page);
 53
 54		spin_lock_irqsave(&zone->lru_lock, flags);
 55		VM_BUG_ON(!PageLRU(page));
 56		__ClearPageLRU(page);
 57		del_page_from_lru(zone, page);
 58		spin_unlock_irqrestore(&zone->lru_lock, flags);
 
 
 
 
 
 
 
 59	}
 60}
 61
 62static void __put_single_page(struct page *page)
 63{
 64	__page_cache_release(page);
 65	free_hot_cold_page(page, 0);
 66}
 67
 68static void __put_compound_page(struct page *page)
 69{
 70	compound_page_dtor *dtor;
 71
 72	__page_cache_release(page);
 73	dtor = get_compound_page_dtor(page);
 74	(*dtor)(page);
 75}
 76
 77static void put_compound_page(struct page *page)
 78{
 79	if (unlikely(PageTail(page))) {
 80		/* __split_huge_page_refcount can run under us */
 81		struct page *page_head = page->first_page;
 82		smp_rmb();
 83		/*
 84		 * If PageTail is still set after smp_rmb() we can be sure
 85		 * that the page->first_page we read wasn't a dangling pointer.
 86		 * See __split_huge_page_refcount() smp_wmb().
 87		 */
 88		if (likely(PageTail(page) && get_page_unless_zero(page_head))) {
 89			unsigned long flags;
 90			/*
 91			 * Verify that our page_head wasn't converted
 92			 * to a a regular page before we got a
 93			 * reference on it.
 94			 */
 95			if (unlikely(!PageHead(page_head))) {
 96				/* PageHead is cleared after PageTail */
 97				smp_rmb();
 98				VM_BUG_ON(PageTail(page));
 99				goto out_put_head;
100			}
101			/*
102			 * Only run compound_lock on a valid PageHead,
103			 * after having it pinned with
104			 * get_page_unless_zero() above.
105			 */
106			smp_mb();
107			/* page_head wasn't a dangling pointer */
108			flags = compound_lock_irqsave(page_head);
109			if (unlikely(!PageTail(page))) {
110				/* __split_huge_page_refcount run before us */
111				compound_unlock_irqrestore(page_head, flags);
112				VM_BUG_ON(PageHead(page_head));
113			out_put_head:
114				if (put_page_testzero(page_head))
115					__put_single_page(page_head);
116			out_put_single:
117				if (put_page_testzero(page))
118					__put_single_page(page);
119				return;
120			}
121			VM_BUG_ON(page_head != page->first_page);
122			/*
123			 * We can release the refcount taken by
124			 * get_page_unless_zero now that
125			 * split_huge_page_refcount is blocked on the
126			 * compound_lock.
127			 */
128			if (put_page_testzero(page_head))
129				VM_BUG_ON(1);
130			/* __split_huge_page_refcount will wait now */
131			VM_BUG_ON(atomic_read(&page->_count) <= 0);
132			atomic_dec(&page->_count);
133			VM_BUG_ON(atomic_read(&page_head->_count) <= 0);
134			compound_unlock_irqrestore(page_head, flags);
135			if (put_page_testzero(page_head)) {
136				if (PageHead(page_head))
137					__put_compound_page(page_head);
138				else
139					__put_single_page(page_head);
140			}
141		} else {
142			/* page_head is a dangling pointer */
143			VM_BUG_ON(PageTail(page));
144			goto out_put_single;
145		}
146	} else if (put_page_testzero(page)) {
147		if (PageHead(page))
148			__put_compound_page(page);
149		else
150			__put_single_page(page);
151	}
152}
153
154void put_page(struct page *page)
155{
156	if (unlikely(PageCompound(page)))
157		put_compound_page(page);
158	else if (put_page_testzero(page))
159		__put_single_page(page);
 
 
160}
161EXPORT_SYMBOL(put_page);
162
163/**
164 * put_pages_list() - release a list of pages
165 * @pages: list of pages threaded on page->lru
166 *
167 * Release a list of pages which are strung together on page.lru.  Currently
168 * used by read_cache_pages() and related error recovery code.
169 */
170void put_pages_list(struct list_head *pages)
171{
172	while (!list_empty(pages)) {
173		struct page *victim;
174
175		victim = list_entry(pages->prev, struct page, lru);
176		list_del(&victim->lru);
177		page_cache_release(victim);
 
 
 
 
 
 
 
 
178	}
 
 
 
179}
180EXPORT_SYMBOL(put_pages_list);
181
182static void pagevec_lru_move_fn(struct pagevec *pvec,
183				void (*move_fn)(struct page *page, void *arg),
184				void *arg)
 
 
 
 
 
 
 
 
 
 
 
 
185{
186	int i;
187	struct zone *zone = NULL;
188	unsigned long flags = 0;
189
190	for (i = 0; i < pagevec_count(pvec); i++) {
191		struct page *page = pvec->pages[i];
192		struct zone *pagezone = page_zone(page);
193
194		if (pagezone != zone) {
195			if (zone)
196				spin_unlock_irqrestore(&zone->lru_lock, flags);
197			zone = pagezone;
198			spin_lock_irqsave(&zone->lru_lock, flags);
199		}
200
201		(*move_fn)(page, arg);
 
202	}
203	if (zone)
204		spin_unlock_irqrestore(&zone->lru_lock, flags);
205	release_pages(pvec->pages, pvec->nr, pvec->cold);
206	pagevec_reinit(pvec);
207}
 
208
209static void pagevec_move_tail_fn(struct page *page, void *arg)
 
 
210{
211	int *pgmoved = arg;
212	struct zone *zone = page_zone(page);
 
 
213
214	if (PageLRU(page) && !PageActive(page) && !PageUnevictable(page)) {
215		enum lru_list lru = page_lru_base_type(page);
216		list_move_tail(&page->lru, &zone->lru[lru].list);
217		mem_cgroup_rotate_reclaimable_page(page);
218		(*pgmoved)++;
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
219	}
 
 
 
220}
221
222/*
223 * pagevec_move_tail() must be called with IRQ disabled.
224 * Otherwise this may cause nasty races.
225 */
226static void pagevec_move_tail(struct pagevec *pvec)
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
227{
228	int pgmoved = 0;
 
 
 
 
229
230	pagevec_lru_move_fn(pvec, pagevec_move_tail_fn, &pgmoved);
231	__count_vm_events(PGROTATED, pgmoved);
 
 
 
 
 
 
232}
233
234/*
235 * Writeback is about to end against a page which has been marked for immediate
236 * reclaim.  If it still appears to be reclaimable, move it to the tail of the
237 * inactive list.
 
 
238 */
239void rotate_reclaimable_page(struct page *page)
240{
241	if (!PageLocked(page) && !PageDirty(page) && !PageActive(page) &&
242	    !PageUnevictable(page) && PageLRU(page)) {
243		struct pagevec *pvec;
244		unsigned long flags;
245
246		page_cache_get(page);
247		local_irq_save(flags);
248		pvec = &__get_cpu_var(lru_rotate_pvecs);
249		if (!pagevec_add(pvec, page))
250			pagevec_move_tail(pvec);
251		local_irq_restore(flags);
252	}
253}
254
255static void update_page_reclaim_stat(struct zone *zone, struct page *page,
256				     int file, int rotated)
257{
258	struct zone_reclaim_stat *reclaim_stat = &zone->reclaim_stat;
259	struct zone_reclaim_stat *memcg_reclaim_stat;
260
261	memcg_reclaim_stat = mem_cgroup_get_reclaim_stat_from_page(page);
 
 
 
 
 
 
 
262
263	reclaim_stat->recent_scanned[file]++;
264	if (rotated)
265		reclaim_stat->recent_rotated[file]++;
266
267	if (!memcg_reclaim_stat)
268		return;
 
 
 
 
 
 
 
 
 
 
 
269
270	memcg_reclaim_stat->recent_scanned[file]++;
271	if (rotated)
272		memcg_reclaim_stat->recent_rotated[file]++;
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
273}
274
275static void __activate_page(struct page *page, void *arg)
276{
277	struct zone *zone = page_zone(page);
 
 
278
279	if (PageLRU(page) && !PageActive(page) && !PageUnevictable(page)) {
280		int file = page_is_file_cache(page);
281		int lru = page_lru_base_type(page);
282		del_page_from_lru_list(zone, page, lru);
283
284		SetPageActive(page);
285		lru += LRU_ACTIVE;
286		add_page_to_lru_list(zone, page, lru);
287		__count_vm_event(PGACTIVATE);
288
289		update_page_reclaim_stat(zone, page, file, 1);
 
 
290	}
291}
292
293#ifdef CONFIG_SMP
294static DEFINE_PER_CPU(struct pagevec, activate_page_pvecs);
295
296static void activate_page_drain(int cpu)
297{
298	struct pagevec *pvec = &per_cpu(activate_page_pvecs, cpu);
299
300	if (pagevec_count(pvec))
301		pagevec_lru_move_fn(pvec, __activate_page, NULL);
302}
303
304void activate_page(struct page *page)
305{
306	if (PageLRU(page) && !PageActive(page) && !PageUnevictable(page)) {
307		struct pagevec *pvec = &get_cpu_var(activate_page_pvecs);
 
308
309		page_cache_get(page);
310		if (!pagevec_add(pvec, page))
311			pagevec_lru_move_fn(pvec, __activate_page, NULL);
312		put_cpu_var(activate_page_pvecs);
 
313	}
314}
315
316#else
317static inline void activate_page_drain(int cpu)
318{
319}
320
321void activate_page(struct page *page)
322{
323	struct zone *zone = page_zone(page);
324
325	spin_lock_irq(&zone->lru_lock);
326	__activate_page(page, NULL);
327	spin_unlock_irq(&zone->lru_lock);
 
 
 
328}
329#endif
330
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
331/*
332 * Mark a page as having seen activity.
333 *
334 * inactive,unreferenced	->	inactive,referenced
335 * inactive,referenced		->	active,unreferenced
336 * active,unreferenced		->	active,referenced
 
 
 
337 */
338void mark_page_accessed(struct page *page)
339{
340	if (!PageActive(page) && !PageUnevictable(page) &&
341			PageReferenced(page) && PageLRU(page)) {
342		activate_page(page);
343		ClearPageReferenced(page);
344	} else if (!PageReferenced(page)) {
345		SetPageReferenced(page);
346	}
347}
348
349EXPORT_SYMBOL(mark_page_accessed);
350
351void __lru_cache_add(struct page *page, enum lru_list lru)
352{
353	struct pagevec *pvec = &get_cpu_var(lru_add_pvecs)[lru];
354
355	page_cache_get(page);
356	if (!pagevec_add(pvec, page))
357		____pagevec_lru_add(pvec, lru);
358	put_cpu_var(lru_add_pvecs);
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
359}
360EXPORT_SYMBOL(__lru_cache_add);
361
362/**
363 * lru_cache_add_lru - add a page to a page list
364 * @page: the page to be added to the LRU.
365 * @lru: the LRU list to which the page is added.
366 */
367void lru_cache_add_lru(struct page *page, enum lru_list lru)
368{
369	if (PageActive(page)) {
370		VM_BUG_ON(PageUnevictable(page));
371		ClearPageActive(page);
372	} else if (PageUnevictable(page)) {
373		VM_BUG_ON(PageActive(page));
374		ClearPageUnevictable(page);
375	}
376
377	VM_BUG_ON(PageLRU(page) || PageActive(page) || PageUnevictable(page));
378	__lru_cache_add(page, lru);
 
 
 
 
 
 
 
 
 
 
 
 
379}
 
380
381/**
382 * add_page_to_unevictable_list - add a page to the unevictable list
383 * @page:  the page to be added to the unevictable list
 
384 *
385 * Add page directly to its zone's unevictable list.  To avoid races with
386 * tasks that might be making the page evictable, through eg. munlock,
387 * munmap or exit, while it's not on the lru, we want to add the page
388 * while it's locked or otherwise "invisible" to other tasks.  This is
389 * difficult to do when using the pagevec cache, so bypass that.
390 */
391void add_page_to_unevictable_list(struct page *page)
392{
393	struct zone *zone = page_zone(page);
394
395	spin_lock_irq(&zone->lru_lock);
396	SetPageUnevictable(page);
397	SetPageLRU(page);
398	add_page_to_lru_list(zone, page, LRU_UNEVICTABLE);
399	spin_unlock_irq(&zone->lru_lock);
400}
401
402/*
403 * If the page can not be invalidated, it is moved to the
404 * inactive list to speed up its reclaim.  It is moved to the
405 * head of the list, rather than the tail, to give the flusher
406 * threads some time to write it out, as this is much more
407 * effective than the single-page writeout from reclaim.
408 *
409 * If the page isn't page_mapped and dirty/writeback, the page
410 * could reclaim asap using PG_reclaim.
411 *
412 * 1. active, mapped page -> none
413 * 2. active, dirty/writeback page -> inactive, head, PG_reclaim
414 * 3. inactive, mapped page -> none
415 * 4. inactive, dirty/writeback page -> inactive, head, PG_reclaim
416 * 5. inactive, clean -> inactive, tail
417 * 6. Others -> none
418 *
419 * In 4, why it moves inactive's head, the VM expects the page would
420 * be write it out by flusher threads as this is much more effective
421 * than the single-page writeout from reclaim.
422 */
423static void lru_deactivate_fn(struct page *page, void *arg)
424{
425	int lru, file;
426	bool active;
427	struct zone *zone = page_zone(page);
428
429	if (!PageLRU(page))
430		return;
431
432	if (PageUnevictable(page))
433		return;
434
435	/* Some processes are using the page */
436	if (page_mapped(page))
437		return;
438
439	active = PageActive(page);
 
 
440
441	file = page_is_file_cache(page);
442	lru = page_lru_base_type(page);
443	del_page_from_lru_list(zone, page, lru + active);
444	ClearPageActive(page);
445	ClearPageReferenced(page);
446	add_page_to_lru_list(zone, page, lru);
447
448	if (PageWriteback(page) || PageDirty(page)) {
449		/*
450		 * PG_reclaim could be raced with end_page_writeback
451		 * It can make readahead confusing.  But race window
452		 * is _really_ small and  it's non-critical problem.
 
453		 */
454		SetPageReclaim(page);
 
455	} else {
456		/*
457		 * The page's writeback ends up during pagevec
458		 * We moves tha page into tail of inactive.
459		 */
460		list_move_tail(&page->lru, &zone->lru[lru].list);
461		mem_cgroup_rotate_reclaimable_page(page);
462		__count_vm_event(PGROTATED);
463	}
464
465	if (active)
466		__count_vm_event(PGDEACTIVATE);
467	update_page_reclaim_stat(zone, page, file, 0);
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
468}
469
470/*
471 * Drain pages out of the cpu's pagevecs.
472 * Either "cpu" is the current CPU, and preemption has already been
473 * disabled; or "cpu" is being hot-unplugged, and is already dead.
474 */
475static void drain_cpu_pagevecs(int cpu)
476{
477	struct pagevec *pvecs = per_cpu(lru_add_pvecs, cpu);
478	struct pagevec *pvec;
479	int lru;
480
481	for_each_lru(lru) {
482		pvec = &pvecs[lru - LRU_BASE];
483		if (pagevec_count(pvec))
484			____pagevec_lru_add(pvec, lru);
485	}
486
487	pvec = &per_cpu(lru_rotate_pvecs, cpu);
488	if (pagevec_count(pvec)) {
 
489		unsigned long flags;
490
491		/* No harm done if a racing interrupt already did this */
492		local_irq_save(flags);
493		pagevec_move_tail(pvec);
494		local_irq_restore(flags);
495	}
496
497	pvec = &per_cpu(lru_deactivate_pvecs, cpu);
498	if (pagevec_count(pvec))
499		pagevec_lru_move_fn(pvec, lru_deactivate_fn, NULL);
 
 
 
 
 
 
 
 
500
501	activate_page_drain(cpu);
502}
503
504/**
505 * deactivate_page - forcefully deactivate a page
506 * @page: page to deactivate
507 *
508 * This function hints the VM that @page is a good reclaim candidate,
509 * for example if its invalidation fails due to the page being dirty
510 * or under writeback.
 
 
511 */
512void deactivate_page(struct page *page)
513{
514	/*
515	 * In a workload with many unevictable page such as mprotect, unevictable
516	 * page deactivation for accelerating reclaim is pointless.
517	 */
518	if (PageUnevictable(page))
519		return;
520
521	if (likely(get_page_unless_zero(page))) {
522		struct pagevec *pvec = &get_cpu_var(lru_deactivate_pvecs);
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
523
524		if (!pagevec_add(pvec, page))
525			pagevec_lru_move_fn(pvec, lru_deactivate_fn, NULL);
526		put_cpu_var(lru_deactivate_pvecs);
 
 
 
 
 
 
 
527	}
528}
529
530void lru_add_drain(void)
531{
532	drain_cpu_pagevecs(get_cpu());
533	put_cpu();
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
534}
535
 
 
 
 
536static void lru_add_drain_per_cpu(struct work_struct *dummy)
537{
538	lru_add_drain();
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
539}
540
541/*
542 * Returns 0 for success
 
 
 
 
543 */
544int lru_add_drain_all(void)
545{
546	return schedule_on_each_cpu(lru_add_drain_per_cpu);
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
547}
548
 
 
 
 
 
 
 
 
 
 
 
 
 
549/*
550 * Batched page_cache_release().  Decrement the reference count on all the
551 * passed pages.  If it fell to zero then remove the page from the LRU and
552 * free it.
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
553 *
554 * Avoid taking zone->lru_lock if possible, but if it is taken, retain it
555 * for the remainder of the operation.
556 *
557 * The locking in this function is against shrink_inactive_list(): we recheck
558 * the page count inside the lock to see whether shrink_inactive_list()
559 * grabbed the page via the LRU.  If it did, give up: shrink_inactive_list()
560 * will free it.
561 */
562void release_pages(struct page **pages, int nr, int cold)
563{
564	int i;
565	struct pagevec pages_to_free;
566	struct zone *zone = NULL;
567	unsigned long uninitialized_var(flags);
 
 
568
569	pagevec_init(&pages_to_free, cold);
570	for (i = 0; i < nr; i++) {
571		struct page *page = pages[i];
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
572
573		if (unlikely(PageCompound(page))) {
574			if (zone) {
575				spin_unlock_irqrestore(&zone->lru_lock, flags);
576				zone = NULL;
577			}
578			put_compound_page(page);
 
 
 
579			continue;
580		}
581
582		if (!put_page_testzero(page))
583			continue;
584
585		if (PageLRU(page)) {
586			struct zone *pagezone = page_zone(page);
587
588			if (pagezone != zone) {
589				if (zone)
590					spin_unlock_irqrestore(&zone->lru_lock,
591									flags);
592				zone = pagezone;
593				spin_lock_irqsave(&zone->lru_lock, flags);
594			}
595			VM_BUG_ON(!PageLRU(page));
596			__ClearPageLRU(page);
597			del_page_from_lru(zone, page);
598		}
599
600		if (!pagevec_add(&pages_to_free, page)) {
601			if (zone) {
602				spin_unlock_irqrestore(&zone->lru_lock, flags);
603				zone = NULL;
604			}
605			__pagevec_free(&pages_to_free);
606			pagevec_reinit(&pages_to_free);
607  		}
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
608	}
609	if (zone)
610		spin_unlock_irqrestore(&zone->lru_lock, flags);
611
612	pagevec_free(&pages_to_free);
 
613}
614EXPORT_SYMBOL(release_pages);
615
616/*
617 * The pages which we're about to release may be in the deferred lru-addition
618 * queues.  That would prevent them from really being freed right now.  That's
619 * OK from a correctness point of view but is inefficient - those pages may be
620 * cache-warm and we want to give them back to the page allocator ASAP.
621 *
622 * So __pagevec_release() will drain those queues here.  __pagevec_lru_add()
623 * and __pagevec_lru_add_active() call release_pages() directly to avoid
624 * mutual recursion.
625 */
626void __pagevec_release(struct pagevec *pvec)
627{
628	lru_add_drain();
629	release_pages(pvec->pages, pagevec_count(pvec), pvec->cold);
 
 
 
630	pagevec_reinit(pvec);
631}
632
633EXPORT_SYMBOL(__pagevec_release);
634
635/* used by __split_huge_page_refcount() */
636void lru_add_page_tail(struct zone* zone,
637		       struct page *page, struct page *page_tail)
638{
639	int active;
640	enum lru_list lru;
641	const int file = 0;
642	struct list_head *head;
643
644	VM_BUG_ON(!PageHead(page));
645	VM_BUG_ON(PageCompound(page_tail));
646	VM_BUG_ON(PageLRU(page_tail));
647	VM_BUG_ON(!spin_is_locked(&zone->lru_lock));
648
649	SetPageLRU(page_tail);
650
651	if (page_evictable(page_tail, NULL)) {
652		if (PageActive(page)) {
653			SetPageActive(page_tail);
654			active = 1;
655			lru = LRU_ACTIVE_ANON;
656		} else {
657			active = 0;
658			lru = LRU_INACTIVE_ANON;
659		}
660		update_page_reclaim_stat(zone, page_tail, file, active);
661		if (likely(PageLRU(page)))
662			head = page->lru.prev;
663		else
664			head = &zone->lru[lru].list;
665		__add_page_to_lru_list(zone, page_tail, lru, head);
666	} else {
667		SetPageUnevictable(page_tail);
668		add_page_to_lru_list(zone, page_tail, LRU_UNEVICTABLE);
669	}
670}
671
672static void ____pagevec_lru_add_fn(struct page *page, void *arg)
673{
674	enum lru_list lru = (enum lru_list)arg;
675	struct zone *zone = page_zone(page);
676	int file = is_file_lru(lru);
677	int active = is_active_lru(lru);
678
679	VM_BUG_ON(PageActive(page));
680	VM_BUG_ON(PageUnevictable(page));
681	VM_BUG_ON(PageLRU(page));
682
683	SetPageLRU(page);
684	if (active)
685		SetPageActive(page);
686	update_page_reclaim_stat(zone, page, file, active);
687	add_page_to_lru_list(zone, page, lru);
688}
689
690/*
691 * Add the passed pages to the LRU, then drop the caller's refcount
692 * on them.  Reinitialises the caller's pagevec.
693 */
694void ____pagevec_lru_add(struct pagevec *pvec, enum lru_list lru)
695{
696	VM_BUG_ON(is_unevictable_lru(lru));
697
698	pagevec_lru_move_fn(pvec, ____pagevec_lru_add_fn, (void *)lru);
699}
700
701EXPORT_SYMBOL(____pagevec_lru_add);
702
703/*
704 * Try to drop buffers from the pages in a pagevec
705 */
706void pagevec_strip(struct pagevec *pvec)
707{
708	int i;
709
710	for (i = 0; i < pagevec_count(pvec); i++) {
711		struct page *page = pvec->pages[i];
712
713		if (page_has_private(page) && trylock_page(page)) {
714			if (page_has_private(page))
715				try_to_release_page(page, 0);
716			unlock_page(page);
717		}
718	}
719}
720
721/**
722 * pagevec_lookup - gang pagecache lookup
723 * @pvec:	Where the resulting pages are placed
724 * @mapping:	The address_space to search
725 * @start:	The starting page index
726 * @nr_pages:	The maximum number of pages
727 *
728 * pagevec_lookup() will search for and return a group of up to @nr_pages pages
729 * in the mapping.  The pages are placed in @pvec.  pagevec_lookup() takes a
730 * reference against the pages in @pvec.
731 *
732 * The search returns a group of mapping-contiguous pages with ascending
733 * indexes.  There may be holes in the indices due to not-present pages.
734 *
735 * pagevec_lookup() returns the number of pages which were found.
736 */
737unsigned pagevec_lookup(struct pagevec *pvec, struct address_space *mapping,
738		pgoff_t start, unsigned nr_pages)
739{
740	pvec->nr = find_get_pages(mapping, start, nr_pages, pvec->pages);
741	return pagevec_count(pvec);
742}
743
744EXPORT_SYMBOL(pagevec_lookup);
 
 
 
 
 
 
745
746unsigned pagevec_lookup_tag(struct pagevec *pvec, struct address_space *mapping,
747		pgoff_t *index, int tag, unsigned nr_pages)
 
748{
749	pvec->nr = find_get_pages_tag(mapping, index, tag,
750					nr_pages, pvec->pages);
751	return pagevec_count(pvec);
752}
753
754EXPORT_SYMBOL(pagevec_lookup_tag);
755
756/*
757 * Perform any setup for the swap system
758 */
759void __init swap_setup(void)
760{
761	unsigned long megs = totalram_pages >> (20 - PAGE_SHIFT);
762
763#ifdef CONFIG_SWAP
764	bdi_init(swapper_space.backing_dev_info);
765#endif
766
767	/* Use a smaller cluster for small-memory machines */
768	if (megs < 16)
769		page_cluster = 2;
770	else
771		page_cluster = 3;
772	/*
773	 * Right now other parts of the system means that we
774	 * _really_ don't want to cluster much more
775	 */
776}
v6.2
   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#include <linux/buffer_head.h>
  40
  41#include "internal.h"
  42
  43#define CREATE_TRACE_POINTS
  44#include <trace/events/pagemap.h>
  45
  46/* How many pages do we try to swap or page in/out together? As a power of 2 */
  47int page_cluster;
  48const int page_cluster_max = 31;
  49
  50/* Protecting only lru_rotate.fbatch which requires disabling interrupts */
  51struct lru_rotate {
  52	local_lock_t lock;
  53	struct folio_batch fbatch;
  54};
  55static DEFINE_PER_CPU(struct lru_rotate, lru_rotate) = {
  56	.lock = INIT_LOCAL_LOCK(lock),
  57};
  58
  59/*
  60 * The following folio batches are grouped together because they are protected
  61 * by disabling preemption (and interrupts remain enabled).
  62 */
  63struct cpu_fbatches {
  64	local_lock_t lock;
  65	struct folio_batch lru_add;
  66	struct folio_batch lru_deactivate_file;
  67	struct folio_batch lru_deactivate;
  68	struct folio_batch lru_lazyfree;
  69#ifdef CONFIG_SMP
  70	struct folio_batch activate;
  71#endif
  72};
  73static DEFINE_PER_CPU(struct cpu_fbatches, cpu_fbatches) = {
  74	.lock = INIT_LOCAL_LOCK(lock),
  75};
  76
  77/*
  78 * This path almost never happens for VM activity - pages are normally freed
  79 * via pagevecs.  But it gets used by networking - and for compound pages.
  80 */
  81static void __page_cache_release(struct folio *folio)
  82{
  83	if (folio_test_lru(folio)) {
  84		struct lruvec *lruvec;
  85		unsigned long flags;
 
  86
  87		lruvec = folio_lruvec_lock_irqsave(folio, &flags);
  88		lruvec_del_folio(lruvec, folio);
  89		__folio_clear_lru_flags(folio);
  90		unlock_page_lruvec_irqrestore(lruvec, flags);
  91	}
  92	/* See comment on folio_test_mlocked in release_pages() */
  93	if (unlikely(folio_test_mlocked(folio))) {
  94		long nr_pages = folio_nr_pages(folio);
  95
  96		__folio_clear_mlocked(folio);
  97		zone_stat_mod_folio(folio, NR_MLOCK, -nr_pages);
  98		count_vm_events(UNEVICTABLE_PGCLEARED, nr_pages);
  99	}
 100}
 101
 102static void __folio_put_small(struct folio *folio)
 
 
 
 
 
 
 103{
 104	__page_cache_release(folio);
 105	mem_cgroup_uncharge(folio);
 106	free_unref_page(&folio->page, 0);
 
 
 107}
 108
 109static void __folio_put_large(struct folio *folio)
 110{
 111	/*
 112	 * __page_cache_release() is supposed to be called for thp, not for
 113	 * hugetlb. This is because hugetlb page does never have PageLRU set
 114	 * (it's never listed to any LRU lists) and no memcg routines should
 115	 * be called for hugetlb (it has a separate hugetlb_cgroup.)
 116	 */
 117	if (!folio_test_hugetlb(folio))
 118		__page_cache_release(folio);
 119	destroy_large_folio(folio);
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 120}
 121
 122void __folio_put(struct folio *folio)
 123{
 124	if (unlikely(folio_is_zone_device(folio)))
 125		free_zone_device_page(&folio->page);
 126	else if (unlikely(folio_test_large(folio)))
 127		__folio_put_large(folio);
 128	else
 129		__folio_put_small(folio);
 130}
 131EXPORT_SYMBOL(__folio_put);
 132
 133/**
 134 * put_pages_list() - release a list of pages
 135 * @pages: list of pages threaded on page->lru
 136 *
 137 * Release a list of pages which are strung together on page.lru.
 
 138 */
 139void put_pages_list(struct list_head *pages)
 140{
 141	struct folio *folio, *next;
 
 142
 143	list_for_each_entry_safe(folio, next, pages, lru) {
 144		if (!folio_put_testzero(folio)) {
 145			list_del(&folio->lru);
 146			continue;
 147		}
 148		if (folio_test_large(folio)) {
 149			list_del(&folio->lru);
 150			__folio_put_large(folio);
 151			continue;
 152		}
 153		/* LRU flag must be clear because it's passed using the lru */
 154	}
 155
 156	free_unref_page_list(pages);
 157	INIT_LIST_HEAD(pages);
 158}
 159EXPORT_SYMBOL(put_pages_list);
 160
 161/*
 162 * get_kernel_pages() - pin kernel pages in memory
 163 * @kiov:	An array of struct kvec structures
 164 * @nr_segs:	number of segments to pin
 165 * @write:	pinning for read/write, currently ignored
 166 * @pages:	array that receives pointers to the pages pinned.
 167 *		Should be at least nr_segs long.
 168 *
 169 * Returns number of pages pinned. This may be fewer than the number requested.
 170 * If nr_segs is 0 or negative, returns 0.  If no pages were pinned, returns 0.
 171 * Each page returned must be released with a put_page() call when it is
 172 * finished with.
 173 */
 174int get_kernel_pages(const struct kvec *kiov, int nr_segs, int write,
 175		struct page **pages)
 176{
 177	int seg;
 
 
 178
 179	for (seg = 0; seg < nr_segs; seg++) {
 180		if (WARN_ON(kiov[seg].iov_len != PAGE_SIZE))
 181			return seg;
 
 
 
 
 
 
 
 182
 183		pages[seg] = kmap_to_page(kiov[seg].iov_base);
 184		get_page(pages[seg]);
 185	}
 186
 187	return seg;
 
 
 188}
 189EXPORT_SYMBOL_GPL(get_kernel_pages);
 190
 191typedef void (*move_fn_t)(struct lruvec *lruvec, struct folio *folio);
 192
 193static void lru_add_fn(struct lruvec *lruvec, struct folio *folio)
 194{
 195	int was_unevictable = folio_test_clear_unevictable(folio);
 196	long nr_pages = folio_nr_pages(folio);
 197
 198	VM_BUG_ON_FOLIO(folio_test_lru(folio), folio);
 199
 200	/*
 201	 * Is an smp_mb__after_atomic() still required here, before
 202	 * folio_evictable() tests the mlocked flag, to rule out the possibility
 203	 * of stranding an evictable folio on an unevictable LRU?  I think
 204	 * not, because __munlock_page() only clears the mlocked flag
 205	 * while the LRU lock is held.
 206	 *
 207	 * (That is not true of __page_cache_release(), and not necessarily
 208	 * true of release_pages(): but those only clear the mlocked flag after
 209	 * folio_put_testzero() has excluded any other users of the folio.)
 210	 */
 211	if (folio_evictable(folio)) {
 212		if (was_unevictable)
 213			__count_vm_events(UNEVICTABLE_PGRESCUED, nr_pages);
 214	} else {
 215		folio_clear_active(folio);
 216		folio_set_unevictable(folio);
 217		/*
 218		 * folio->mlock_count = !!folio_test_mlocked(folio)?
 219		 * But that leaves __mlock_page() in doubt whether another
 220		 * actor has already counted the mlock or not.  Err on the
 221		 * safe side, underestimate, let page reclaim fix it, rather
 222		 * than leaving a page on the unevictable LRU indefinitely.
 223		 */
 224		folio->mlock_count = 0;
 225		if (!was_unevictable)
 226			__count_vm_events(UNEVICTABLE_PGCULLED, nr_pages);
 227	}
 228
 229	lruvec_add_folio(lruvec, folio);
 230	trace_mm_lru_insertion(folio);
 231}
 232
 233static void folio_batch_move_lru(struct folio_batch *fbatch, move_fn_t move_fn)
 234{
 235	int i;
 236	struct lruvec *lruvec = NULL;
 237	unsigned long flags = 0;
 238
 239	for (i = 0; i < folio_batch_count(fbatch); i++) {
 240		struct folio *folio = fbatch->folios[i];
 241
 242		/* block memcg migration while the folio moves between lru */
 243		if (move_fn != lru_add_fn && !folio_test_clear_lru(folio))
 244			continue;
 245
 246		lruvec = folio_lruvec_relock_irqsave(folio, lruvec, &flags);
 247		move_fn(lruvec, folio);
 248
 249		folio_set_lru(folio);
 250	}
 251
 252	if (lruvec)
 253		unlock_page_lruvec_irqrestore(lruvec, flags);
 254	folios_put(fbatch->folios, folio_batch_count(fbatch));
 255	folio_batch_init(fbatch);
 256}
 257
 258static void folio_batch_add_and_move(struct folio_batch *fbatch,
 259		struct folio *folio, move_fn_t move_fn)
 260{
 261	if (folio_batch_add(fbatch, folio) && !folio_test_large(folio) &&
 262	    !lru_cache_disabled())
 263		return;
 264	folio_batch_move_lru(fbatch, move_fn);
 265}
 266
 267static void lru_move_tail_fn(struct lruvec *lruvec, struct folio *folio)
 268{
 269	if (!folio_test_unevictable(folio)) {
 270		lruvec_del_folio(lruvec, folio);
 271		folio_clear_active(folio);
 272		lruvec_add_folio_tail(lruvec, folio);
 273		__count_vm_events(PGROTATED, folio_nr_pages(folio));
 274	}
 275}
 276
 277/*
 278 * Writeback is about to end against a folio which has been marked for
 279 * immediate reclaim.  If it still appears to be reclaimable, move it
 280 * to the tail of the inactive list.
 281 *
 282 * folio_rotate_reclaimable() must disable IRQs, to prevent nasty races.
 283 */
 284void folio_rotate_reclaimable(struct folio *folio)
 285{
 286	if (!folio_test_locked(folio) && !folio_test_dirty(folio) &&
 287	    !folio_test_unevictable(folio) && folio_test_lru(folio)) {
 288		struct folio_batch *fbatch;
 289		unsigned long flags;
 290
 291		folio_get(folio);
 292		local_lock_irqsave(&lru_rotate.lock, flags);
 293		fbatch = this_cpu_ptr(&lru_rotate.fbatch);
 294		folio_batch_add_and_move(fbatch, folio, lru_move_tail_fn);
 295		local_unlock_irqrestore(&lru_rotate.lock, flags);
 
 296	}
 297}
 298
 299void lru_note_cost(struct lruvec *lruvec, bool file,
 300		   unsigned int nr_io, unsigned int nr_rotated)
 301{
 302	unsigned long cost;
 
 303
 304	/*
 305	 * Reflect the relative cost of incurring IO and spending CPU
 306	 * time on rotations. This doesn't attempt to make a precise
 307	 * comparison, it just says: if reloads are about comparable
 308	 * between the LRU lists, or rotations are overwhelmingly
 309	 * different between them, adjust scan balance for CPU work.
 310	 */
 311	cost = nr_io * SWAP_CLUSTER_MAX + nr_rotated;
 312
 313	do {
 314		unsigned long lrusize;
 
 315
 316		/*
 317		 * Hold lruvec->lru_lock is safe here, since
 318		 * 1) The pinned lruvec in reclaim, or
 319		 * 2) From a pre-LRU page during refault (which also holds the
 320		 *    rcu lock, so would be safe even if the page was on the LRU
 321		 *    and could move simultaneously to a new lruvec).
 322		 */
 323		spin_lock_irq(&lruvec->lru_lock);
 324		/* Record cost event */
 325		if (file)
 326			lruvec->file_cost += cost;
 327		else
 328			lruvec->anon_cost += cost;
 329
 330		/*
 331		 * Decay previous events
 332		 *
 333		 * Because workloads change over time (and to avoid
 334		 * overflow) we keep these statistics as a floating
 335		 * average, which ends up weighing recent refaults
 336		 * more than old ones.
 337		 */
 338		lrusize = lruvec_page_state(lruvec, NR_INACTIVE_ANON) +
 339			  lruvec_page_state(lruvec, NR_ACTIVE_ANON) +
 340			  lruvec_page_state(lruvec, NR_INACTIVE_FILE) +
 341			  lruvec_page_state(lruvec, NR_ACTIVE_FILE);
 342
 343		if (lruvec->file_cost + lruvec->anon_cost > lrusize / 4) {
 344			lruvec->file_cost /= 2;
 345			lruvec->anon_cost /= 2;
 346		}
 347		spin_unlock_irq(&lruvec->lru_lock);
 348	} while ((lruvec = parent_lruvec(lruvec)));
 349}
 350
 351void lru_note_cost_refault(struct folio *folio)
 352{
 353	lru_note_cost(folio_lruvec(folio), folio_is_file_lru(folio),
 354		      folio_nr_pages(folio), 0);
 355}
 356
 357static void folio_activate_fn(struct lruvec *lruvec, struct folio *folio)
 358{
 359	if (!folio_test_active(folio) && !folio_test_unevictable(folio)) {
 360		long nr_pages = folio_nr_pages(folio);
 361
 362		lruvec_del_folio(lruvec, folio);
 363		folio_set_active(folio);
 364		lruvec_add_folio(lruvec, folio);
 365		trace_mm_lru_activate(folio);
 366
 367		__count_vm_events(PGACTIVATE, nr_pages);
 368		__count_memcg_events(lruvec_memcg(lruvec), PGACTIVATE,
 369				     nr_pages);
 370	}
 371}
 372
 373#ifdef CONFIG_SMP
 374static void folio_activate_drain(int cpu)
 
 
 375{
 376	struct folio_batch *fbatch = &per_cpu(cpu_fbatches.activate, cpu);
 377
 378	if (folio_batch_count(fbatch))
 379		folio_batch_move_lru(fbatch, folio_activate_fn);
 380}
 381
 382void folio_activate(struct folio *folio)
 383{
 384	if (folio_test_lru(folio) && !folio_test_active(folio) &&
 385	    !folio_test_unevictable(folio)) {
 386		struct folio_batch *fbatch;
 387
 388		folio_get(folio);
 389		local_lock(&cpu_fbatches.lock);
 390		fbatch = this_cpu_ptr(&cpu_fbatches.activate);
 391		folio_batch_add_and_move(fbatch, folio, folio_activate_fn);
 392		local_unlock(&cpu_fbatches.lock);
 393	}
 394}
 395
 396#else
 397static inline void folio_activate_drain(int cpu)
 398{
 399}
 400
 401void folio_activate(struct folio *folio)
 402{
 403	struct lruvec *lruvec;
 404
 405	if (folio_test_clear_lru(folio)) {
 406		lruvec = folio_lruvec_lock_irq(folio);
 407		folio_activate_fn(lruvec, folio);
 408		unlock_page_lruvec_irq(lruvec);
 409		folio_set_lru(folio);
 410	}
 411}
 412#endif
 413
 414static void __lru_cache_activate_folio(struct folio *folio)
 415{
 416	struct folio_batch *fbatch;
 417	int i;
 418
 419	local_lock(&cpu_fbatches.lock);
 420	fbatch = this_cpu_ptr(&cpu_fbatches.lru_add);
 421
 422	/*
 423	 * Search backwards on the optimistic assumption that the folio being
 424	 * activated has just been added to this batch. Note that only
 425	 * the local batch is examined as a !LRU folio could be in the
 426	 * process of being released, reclaimed, migrated or on a remote
 427	 * batch that is currently being drained. Furthermore, marking
 428	 * a remote batch's folio active potentially hits a race where
 429	 * a folio is marked active just after it is added to the inactive
 430	 * list causing accounting errors and BUG_ON checks to trigger.
 431	 */
 432	for (i = folio_batch_count(fbatch) - 1; i >= 0; i--) {
 433		struct folio *batch_folio = fbatch->folios[i];
 434
 435		if (batch_folio == folio) {
 436			folio_set_active(folio);
 437			break;
 438		}
 439	}
 440
 441	local_unlock(&cpu_fbatches.lock);
 442}
 443
 444#ifdef CONFIG_LRU_GEN
 445static void folio_inc_refs(struct folio *folio)
 446{
 447	unsigned long new_flags, old_flags = READ_ONCE(folio->flags);
 448
 449	if (folio_test_unevictable(folio))
 450		return;
 451
 452	if (!folio_test_referenced(folio)) {
 453		folio_set_referenced(folio);
 454		return;
 455	}
 456
 457	if (!folio_test_workingset(folio)) {
 458		folio_set_workingset(folio);
 459		return;
 460	}
 461
 462	/* see the comment on MAX_NR_TIERS */
 463	do {
 464		new_flags = old_flags & LRU_REFS_MASK;
 465		if (new_flags == LRU_REFS_MASK)
 466			break;
 467
 468		new_flags += BIT(LRU_REFS_PGOFF);
 469		new_flags |= old_flags & ~LRU_REFS_MASK;
 470	} while (!try_cmpxchg(&folio->flags, &old_flags, new_flags));
 471}
 472#else
 473static void folio_inc_refs(struct folio *folio)
 474{
 475}
 476#endif /* CONFIG_LRU_GEN */
 477
 478/*
 479 * Mark a page as having seen activity.
 480 *
 481 * inactive,unreferenced	->	inactive,referenced
 482 * inactive,referenced		->	active,unreferenced
 483 * active,unreferenced		->	active,referenced
 484 *
 485 * When a newly allocated page is not yet visible, so safe for non-atomic ops,
 486 * __SetPageReferenced(page) may be substituted for mark_page_accessed(page).
 487 */
 488void folio_mark_accessed(struct folio *folio)
 489{
 490	if (lru_gen_enabled()) {
 491		folio_inc_refs(folio);
 492		return;
 
 
 
 493	}
 
 
 
 
 
 
 
 494
 495	if (!folio_test_referenced(folio)) {
 496		folio_set_referenced(folio);
 497	} else if (folio_test_unevictable(folio)) {
 498		/*
 499		 * Unevictable pages are on the "LRU_UNEVICTABLE" list. But,
 500		 * this list is never rotated or maintained, so marking an
 501		 * unevictable page accessed has no effect.
 502		 */
 503	} else if (!folio_test_active(folio)) {
 504		/*
 505		 * If the folio is on the LRU, queue it for activation via
 506		 * cpu_fbatches.activate. Otherwise, assume the folio is in a
 507		 * folio_batch, mark it active and it'll be moved to the active
 508		 * LRU on the next drain.
 509		 */
 510		if (folio_test_lru(folio))
 511			folio_activate(folio);
 512		else
 513			__lru_cache_activate_folio(folio);
 514		folio_clear_referenced(folio);
 515		workingset_activation(folio);
 516	}
 517	if (folio_test_idle(folio))
 518		folio_clear_idle(folio);
 519}
 520EXPORT_SYMBOL(folio_mark_accessed);
 521
 522/**
 523 * folio_add_lru - Add a folio to an LRU list.
 524 * @folio: The folio to be added to the LRU.
 525 *
 526 * Queue the folio for addition to the LRU. The decision on whether
 527 * to add the page to the [in]active [file|anon] list is deferred until the
 528 * folio_batch is drained. This gives a chance for the caller of folio_add_lru()
 529 * have the folio added to the active list using folio_mark_accessed().
 530 */
 531void folio_add_lru(struct folio *folio)
 532{
 533	struct folio_batch *fbatch;
 
 
 534
 535	VM_BUG_ON_FOLIO(folio_test_active(folio) &&
 536			folio_test_unevictable(folio), folio);
 537	VM_BUG_ON_FOLIO(folio_test_lru(folio), folio);
 538
 539	/* see the comment in lru_gen_add_folio() */
 540	if (lru_gen_enabled() && !folio_test_unevictable(folio) &&
 541	    lru_gen_in_fault() && !(current->flags & PF_MEMALLOC))
 542		folio_set_active(folio);
 543
 544	folio_get(folio);
 545	local_lock(&cpu_fbatches.lock);
 546	fbatch = this_cpu_ptr(&cpu_fbatches.lru_add);
 547	folio_batch_add_and_move(fbatch, folio, lru_add_fn);
 548	local_unlock(&cpu_fbatches.lock);
 549}
 550EXPORT_SYMBOL(folio_add_lru);
 551
 552/**
 553 * folio_add_lru_vma() - Add a folio to the appropate LRU list for this VMA.
 554 * @folio: The folio to be added to the LRU.
 555 * @vma: VMA in which the folio is mapped.
 556 *
 557 * If the VMA is mlocked, @folio is added to the unevictable list.
 558 * Otherwise, it is treated the same way as folio_add_lru().
 
 
 
 559 */
 560void folio_add_lru_vma(struct folio *folio, struct vm_area_struct *vma)
 561{
 562	VM_BUG_ON_FOLIO(folio_test_lru(folio), folio);
 563
 564	if (unlikely((vma->vm_flags & (VM_LOCKED | VM_SPECIAL)) == VM_LOCKED))
 565		mlock_new_page(&folio->page);
 566	else
 567		folio_add_lru(folio);
 
 568}
 569
 570/*
 571 * If the folio cannot be invalidated, it is moved to the
 572 * inactive list to speed up its reclaim.  It is moved to the
 573 * head of the list, rather than the tail, to give the flusher
 574 * threads some time to write it out, as this is much more
 575 * effective than the single-page writeout from reclaim.
 576 *
 577 * If the folio isn't mapped and dirty/writeback, the folio
 578 * could be reclaimed asap using the reclaim flag.
 579 *
 580 * 1. active, mapped folio -> none
 581 * 2. active, dirty/writeback folio -> inactive, head, reclaim
 582 * 3. inactive, mapped folio -> none
 583 * 4. inactive, dirty/writeback folio -> inactive, head, reclaim
 584 * 5. inactive, clean -> inactive, tail
 585 * 6. Others -> none
 586 *
 587 * In 4, it moves to the head of the inactive list so the folio is
 588 * written out by flusher threads as this is much more efficient
 589 * than the single-page writeout from reclaim.
 590 */
 591static void lru_deactivate_file_fn(struct lruvec *lruvec, struct folio *folio)
 592{
 593	bool active = folio_test_active(folio);
 594	long nr_pages = folio_nr_pages(folio);
 
 
 
 
 595
 596	if (folio_test_unevictable(folio))
 597		return;
 598
 599	/* Some processes are using the folio */
 600	if (folio_mapped(folio))
 601		return;
 602
 603	lruvec_del_folio(lruvec, folio);
 604	folio_clear_active(folio);
 605	folio_clear_referenced(folio);
 606
 607	if (folio_test_writeback(folio) || folio_test_dirty(folio)) {
 
 
 
 
 
 
 
 608		/*
 609		 * Setting the reclaim flag could race with
 610		 * folio_end_writeback() and confuse readahead.  But the
 611		 * race window is _really_ small and  it's not a critical
 612		 * problem.
 613		 */
 614		lruvec_add_folio(lruvec, folio);
 615		folio_set_reclaim(folio);
 616	} else {
 617		/*
 618		 * The folio's writeback ended while it was in the batch.
 619		 * We move that folio to the tail of the inactive list.
 620		 */
 621		lruvec_add_folio_tail(lruvec, folio);
 622		__count_vm_events(PGROTATED, nr_pages);
 
 623	}
 624
 625	if (active) {
 626		__count_vm_events(PGDEACTIVATE, nr_pages);
 627		__count_memcg_events(lruvec_memcg(lruvec), PGDEACTIVATE,
 628				     nr_pages);
 629	}
 630}
 631
 632static void lru_deactivate_fn(struct lruvec *lruvec, struct folio *folio)
 633{
 634	if (!folio_test_unevictable(folio) && (folio_test_active(folio) || lru_gen_enabled())) {
 635		long nr_pages = folio_nr_pages(folio);
 636
 637		lruvec_del_folio(lruvec, folio);
 638		folio_clear_active(folio);
 639		folio_clear_referenced(folio);
 640		lruvec_add_folio(lruvec, folio);
 641
 642		__count_vm_events(PGDEACTIVATE, nr_pages);
 643		__count_memcg_events(lruvec_memcg(lruvec), PGDEACTIVATE,
 644				     nr_pages);
 645	}
 646}
 647
 648static void lru_lazyfree_fn(struct lruvec *lruvec, struct folio *folio)
 649{
 650	if (folio_test_anon(folio) && folio_test_swapbacked(folio) &&
 651	    !folio_test_swapcache(folio) && !folio_test_unevictable(folio)) {
 652		long nr_pages = folio_nr_pages(folio);
 653
 654		lruvec_del_folio(lruvec, folio);
 655		folio_clear_active(folio);
 656		folio_clear_referenced(folio);
 657		/*
 658		 * Lazyfree folios are clean anonymous folios.  They have
 659		 * the swapbacked flag cleared, to distinguish them from normal
 660		 * anonymous folios
 661		 */
 662		folio_clear_swapbacked(folio);
 663		lruvec_add_folio(lruvec, folio);
 664
 665		__count_vm_events(PGLAZYFREE, nr_pages);
 666		__count_memcg_events(lruvec_memcg(lruvec), PGLAZYFREE,
 667				     nr_pages);
 668	}
 669}
 670
 671/*
 672 * Drain pages out of the cpu's folio_batch.
 673 * Either "cpu" is the current CPU, and preemption has already been
 674 * disabled; or "cpu" is being hot-unplugged, and is already dead.
 675 */
 676void lru_add_drain_cpu(int cpu)
 677{
 678	struct cpu_fbatches *fbatches = &per_cpu(cpu_fbatches, cpu);
 679	struct folio_batch *fbatch = &fbatches->lru_add;
 
 680
 681	if (folio_batch_count(fbatch))
 682		folio_batch_move_lru(fbatch, lru_add_fn);
 
 
 
 683
 684	fbatch = &per_cpu(lru_rotate.fbatch, cpu);
 685	/* Disabling interrupts below acts as a compiler barrier. */
 686	if (data_race(folio_batch_count(fbatch))) {
 687		unsigned long flags;
 688
 689		/* No harm done if a racing interrupt already did this */
 690		local_lock_irqsave(&lru_rotate.lock, flags);
 691		folio_batch_move_lru(fbatch, lru_move_tail_fn);
 692		local_unlock_irqrestore(&lru_rotate.lock, flags);
 693	}
 694
 695	fbatch = &fbatches->lru_deactivate_file;
 696	if (folio_batch_count(fbatch))
 697		folio_batch_move_lru(fbatch, lru_deactivate_file_fn);
 698
 699	fbatch = &fbatches->lru_deactivate;
 700	if (folio_batch_count(fbatch))
 701		folio_batch_move_lru(fbatch, lru_deactivate_fn);
 702
 703	fbatch = &fbatches->lru_lazyfree;
 704	if (folio_batch_count(fbatch))
 705		folio_batch_move_lru(fbatch, lru_lazyfree_fn);
 706
 707	folio_activate_drain(cpu);
 708}
 709
 710/**
 711 * deactivate_file_folio() - Deactivate a file folio.
 712 * @folio: Folio to deactivate.
 713 *
 714 * This function hints to the VM that @folio is a good reclaim candidate,
 715 * for example if its invalidation fails due to the folio being dirty
 716 * or under writeback.
 717 *
 718 * Context: Caller holds a reference on the folio.
 719 */
 720void deactivate_file_folio(struct folio *folio)
 721{
 722	struct folio_batch *fbatch;
 723
 724	/* Deactivating an unevictable folio will not accelerate reclaim */
 725	if (folio_test_unevictable(folio))
 
 726		return;
 727
 728	folio_get(folio);
 729	local_lock(&cpu_fbatches.lock);
 730	fbatch = this_cpu_ptr(&cpu_fbatches.lru_deactivate_file);
 731	folio_batch_add_and_move(fbatch, folio, lru_deactivate_file_fn);
 732	local_unlock(&cpu_fbatches.lock);
 733}
 734
 735/*
 736 * deactivate_page - deactivate a page
 737 * @page: page to deactivate
 738 *
 739 * deactivate_page() moves @page to the inactive list if @page was on the active
 740 * list and was not an unevictable page.  This is done to accelerate the reclaim
 741 * of @page.
 742 */
 743void deactivate_page(struct page *page)
 744{
 745	struct folio *folio = page_folio(page);
 746
 747	if (folio_test_lru(folio) && !folio_test_unevictable(folio) &&
 748	    (folio_test_active(folio) || lru_gen_enabled())) {
 749		struct folio_batch *fbatch;
 750
 751		folio_get(folio);
 752		local_lock(&cpu_fbatches.lock);
 753		fbatch = this_cpu_ptr(&cpu_fbatches.lru_deactivate);
 754		folio_batch_add_and_move(fbatch, folio, lru_deactivate_fn);
 755		local_unlock(&cpu_fbatches.lock);
 756	}
 757}
 758
 759/**
 760 * mark_page_lazyfree - make an anon page lazyfree
 761 * @page: page to deactivate
 762 *
 763 * mark_page_lazyfree() moves @page to the inactive file list.
 764 * This is done to accelerate the reclaim of @page.
 765 */
 766void mark_page_lazyfree(struct page *page)
 767{
 768	struct folio *folio = page_folio(page);
 769
 770	if (folio_test_lru(folio) && folio_test_anon(folio) &&
 771	    folio_test_swapbacked(folio) && !folio_test_swapcache(folio) &&
 772	    !folio_test_unevictable(folio)) {
 773		struct folio_batch *fbatch;
 774
 775		folio_get(folio);
 776		local_lock(&cpu_fbatches.lock);
 777		fbatch = this_cpu_ptr(&cpu_fbatches.lru_lazyfree);
 778		folio_batch_add_and_move(fbatch, folio, lru_lazyfree_fn);
 779		local_unlock(&cpu_fbatches.lock);
 780	}
 781}
 782
 783void lru_add_drain(void)
 784{
 785	local_lock(&cpu_fbatches.lock);
 786	lru_add_drain_cpu(smp_processor_id());
 787	local_unlock(&cpu_fbatches.lock);
 788	mlock_page_drain_local();
 789}
 790
 791/*
 792 * It's called from per-cpu workqueue context in SMP case so
 793 * lru_add_drain_cpu and invalidate_bh_lrus_cpu should run on
 794 * the same cpu. It shouldn't be a problem in !SMP case since
 795 * the core is only one and the locks will disable preemption.
 796 */
 797static void lru_add_and_bh_lrus_drain(void)
 798{
 799	local_lock(&cpu_fbatches.lock);
 800	lru_add_drain_cpu(smp_processor_id());
 801	local_unlock(&cpu_fbatches.lock);
 802	invalidate_bh_lrus_cpu();
 803	mlock_page_drain_local();
 804}
 805
 806void lru_add_drain_cpu_zone(struct zone *zone)
 807{
 808	local_lock(&cpu_fbatches.lock);
 809	lru_add_drain_cpu(smp_processor_id());
 810	drain_local_pages(zone);
 811	local_unlock(&cpu_fbatches.lock);
 812	mlock_page_drain_local();
 813}
 814
 815#ifdef CONFIG_SMP
 816
 817static DEFINE_PER_CPU(struct work_struct, lru_add_drain_work);
 818
 819static void lru_add_drain_per_cpu(struct work_struct *dummy)
 820{
 821	lru_add_and_bh_lrus_drain();
 822}
 823
 824static bool cpu_needs_drain(unsigned int cpu)
 825{
 826	struct cpu_fbatches *fbatches = &per_cpu(cpu_fbatches, cpu);
 827
 828	/* Check these in order of likelihood that they're not zero */
 829	return folio_batch_count(&fbatches->lru_add) ||
 830		data_race(folio_batch_count(&per_cpu(lru_rotate.fbatch, cpu))) ||
 831		folio_batch_count(&fbatches->lru_deactivate_file) ||
 832		folio_batch_count(&fbatches->lru_deactivate) ||
 833		folio_batch_count(&fbatches->lru_lazyfree) ||
 834		folio_batch_count(&fbatches->activate) ||
 835		need_mlock_page_drain(cpu) ||
 836		has_bh_in_lru(cpu, NULL);
 837}
 838
 839/*
 840 * Doesn't need any cpu hotplug locking because we do rely on per-cpu
 841 * kworkers being shut down before our page_alloc_cpu_dead callback is
 842 * executed on the offlined cpu.
 843 * Calling this function with cpu hotplug locks held can actually lead
 844 * to obscure indirect dependencies via WQ context.
 845 */
 846static inline void __lru_add_drain_all(bool force_all_cpus)
 847{
 848	/*
 849	 * lru_drain_gen - Global pages generation number
 850	 *
 851	 * (A) Definition: global lru_drain_gen = x implies that all generations
 852	 *     0 < n <= x are already *scheduled* for draining.
 853	 *
 854	 * This is an optimization for the highly-contended use case where a
 855	 * user space workload keeps constantly generating a flow of pages for
 856	 * each CPU.
 857	 */
 858	static unsigned int lru_drain_gen;
 859	static struct cpumask has_work;
 860	static DEFINE_MUTEX(lock);
 861	unsigned cpu, this_gen;
 862
 863	/*
 864	 * Make sure nobody triggers this path before mm_percpu_wq is fully
 865	 * initialized.
 866	 */
 867	if (WARN_ON(!mm_percpu_wq))
 868		return;
 869
 870	/*
 871	 * Guarantee folio_batch counter stores visible by this CPU
 872	 * are visible to other CPUs before loading the current drain
 873	 * generation.
 874	 */
 875	smp_mb();
 876
 877	/*
 878	 * (B) Locally cache global LRU draining generation number
 879	 *
 880	 * The read barrier ensures that the counter is loaded before the mutex
 881	 * is taken. It pairs with smp_mb() inside the mutex critical section
 882	 * at (D).
 883	 */
 884	this_gen = smp_load_acquire(&lru_drain_gen);
 885
 886	mutex_lock(&lock);
 887
 888	/*
 889	 * (C) Exit the draining operation if a newer generation, from another
 890	 * lru_add_drain_all(), was already scheduled for draining. Check (A).
 891	 */
 892	if (unlikely(this_gen != lru_drain_gen && !force_all_cpus))
 893		goto done;
 894
 895	/*
 896	 * (D) Increment global generation number
 897	 *
 898	 * Pairs with smp_load_acquire() at (B), outside of the critical
 899	 * section. Use a full memory barrier to guarantee that the
 900	 * new global drain generation number is stored before loading
 901	 * folio_batch counters.
 902	 *
 903	 * This pairing must be done here, before the for_each_online_cpu loop
 904	 * below which drains the page vectors.
 905	 *
 906	 * Let x, y, and z represent some system CPU numbers, where x < y < z.
 907	 * Assume CPU #z is in the middle of the for_each_online_cpu loop
 908	 * below and has already reached CPU #y's per-cpu data. CPU #x comes
 909	 * along, adds some pages to its per-cpu vectors, then calls
 910	 * lru_add_drain_all().
 911	 *
 912	 * If the paired barrier is done at any later step, e.g. after the
 913	 * loop, CPU #x will just exit at (C) and miss flushing out all of its
 914	 * added pages.
 915	 */
 916	WRITE_ONCE(lru_drain_gen, lru_drain_gen + 1);
 917	smp_mb();
 918
 919	cpumask_clear(&has_work);
 920	for_each_online_cpu(cpu) {
 921		struct work_struct *work = &per_cpu(lru_add_drain_work, cpu);
 922
 923		if (cpu_needs_drain(cpu)) {
 924			INIT_WORK(work, lru_add_drain_per_cpu);
 925			queue_work_on(cpu, mm_percpu_wq, work);
 926			__cpumask_set_cpu(cpu, &has_work);
 927		}
 928	}
 929
 930	for_each_cpu(cpu, &has_work)
 931		flush_work(&per_cpu(lru_add_drain_work, cpu));
 932
 933done:
 934	mutex_unlock(&lock);
 935}
 936
 937void lru_add_drain_all(void)
 938{
 939	__lru_add_drain_all(false);
 940}
 941#else
 942void lru_add_drain_all(void)
 943{
 944	lru_add_drain();
 945}
 946#endif /* CONFIG_SMP */
 947
 948atomic_t lru_disable_count = ATOMIC_INIT(0);
 949
 950/*
 951 * lru_cache_disable() needs to be called before we start compiling
 952 * a list of pages to be migrated using isolate_lru_page().
 953 * It drains pages on LRU cache and then disable on all cpus until
 954 * lru_cache_enable is called.
 955 *
 956 * Must be paired with a call to lru_cache_enable().
 957 */
 958void lru_cache_disable(void)
 959{
 960	atomic_inc(&lru_disable_count);
 961	/*
 962	 * Readers of lru_disable_count are protected by either disabling
 963	 * preemption or rcu_read_lock:
 964	 *
 965	 * preempt_disable, local_irq_disable  [bh_lru_lock()]
 966	 * rcu_read_lock		       [rt_spin_lock CONFIG_PREEMPT_RT]
 967	 * preempt_disable		       [local_lock !CONFIG_PREEMPT_RT]
 968	 *
 969	 * Since v5.1 kernel, synchronize_rcu() is guaranteed to wait on
 970	 * preempt_disable() regions of code. So any CPU which sees
 971	 * lru_disable_count = 0 will have exited the critical
 972	 * section when synchronize_rcu() returns.
 973	 */
 974	synchronize_rcu_expedited();
 975#ifdef CONFIG_SMP
 976	__lru_add_drain_all(true);
 977#else
 978	lru_add_and_bh_lrus_drain();
 979#endif
 980}
 981
 982/**
 983 * release_pages - batched put_page()
 984 * @arg: array of pages to release
 985 * @nr: number of pages
 986 *
 987 * Decrement the reference count on all the pages in @arg.  If it
 988 * fell to zero, remove the page from the LRU and free it.
 989 *
 990 * Note that the argument can be an array of pages, encoded pages,
 991 * or folio pointers. We ignore any encoded bits, and turn any of
 992 * them into just a folio that gets free'd.
 
 993 */
 994void release_pages(release_pages_arg arg, int nr)
 995{
 996	int i;
 997	struct encoded_page **encoded = arg.encoded_pages;
 998	LIST_HEAD(pages_to_free);
 999	struct lruvec *lruvec = NULL;
1000	unsigned long flags = 0;
1001	unsigned int lock_batch;
1002
 
1003	for (i = 0; i < nr; i++) {
1004		struct folio *folio;
1005
1006		/* Turn any of the argument types into a folio */
1007		folio = page_folio(encoded_page_ptr(encoded[i]));
1008
1009		/*
1010		 * Make sure the IRQ-safe lock-holding time does not get
1011		 * excessive with a continuous string of pages from the
1012		 * same lruvec. The lock is held only if lruvec != NULL.
1013		 */
1014		if (lruvec && ++lock_batch == SWAP_CLUSTER_MAX) {
1015			unlock_page_lruvec_irqrestore(lruvec, flags);
1016			lruvec = NULL;
1017		}
1018
1019		if (is_huge_zero_page(&folio->page))
1020			continue;
1021
1022		if (folio_is_zone_device(folio)) {
1023			if (lruvec) {
1024				unlock_page_lruvec_irqrestore(lruvec, flags);
1025				lruvec = NULL;
1026			}
1027			if (put_devmap_managed_page(&folio->page))
1028				continue;
1029			if (folio_put_testzero(folio))
1030				free_zone_device_page(&folio->page);
1031			continue;
1032		}
1033
1034		if (!folio_put_testzero(folio))
1035			continue;
1036
1037		if (folio_test_large(folio)) {
1038			if (lruvec) {
1039				unlock_page_lruvec_irqrestore(lruvec, flags);
1040				lruvec = NULL;
 
 
 
 
 
1041			}
1042			__folio_put_large(folio);
1043			continue;
 
1044		}
1045
1046		if (folio_test_lru(folio)) {
1047			struct lruvec *prev_lruvec = lruvec;
1048
1049			lruvec = folio_lruvec_relock_irqsave(folio, lruvec,
1050									&flags);
1051			if (prev_lruvec != lruvec)
1052				lock_batch = 0;
1053
1054			lruvec_del_folio(lruvec, folio);
1055			__folio_clear_lru_flags(folio);
1056		}
1057
1058		/*
1059		 * In rare cases, when truncation or holepunching raced with
1060		 * munlock after VM_LOCKED was cleared, Mlocked may still be
1061		 * found set here.  This does not indicate a problem, unless
1062		 * "unevictable_pgs_cleared" appears worryingly large.
1063		 */
1064		if (unlikely(folio_test_mlocked(folio))) {
1065			__folio_clear_mlocked(folio);
1066			zone_stat_sub_folio(folio, NR_MLOCK);
1067			count_vm_event(UNEVICTABLE_PGCLEARED);
1068		}
1069
1070		list_add(&folio->lru, &pages_to_free);
1071	}
1072	if (lruvec)
1073		unlock_page_lruvec_irqrestore(lruvec, flags);
1074
1075	mem_cgroup_uncharge_list(&pages_to_free);
1076	free_unref_page_list(&pages_to_free);
1077}
1078EXPORT_SYMBOL(release_pages);
1079
1080/*
1081 * The pages which we're about to release may be in the deferred lru-addition
1082 * queues.  That would prevent them from really being freed right now.  That's
1083 * OK from a correctness point of view but is inefficient - those pages may be
1084 * cache-warm and we want to give them back to the page allocator ASAP.
1085 *
1086 * So __pagevec_release() will drain those queues here.
1087 * folio_batch_move_lru() calls folios_put() directly to avoid
1088 * mutual recursion.
1089 */
1090void __pagevec_release(struct pagevec *pvec)
1091{
1092	if (!pvec->percpu_pvec_drained) {
1093		lru_add_drain();
1094		pvec->percpu_pvec_drained = true;
1095	}
1096	release_pages(pvec->pages, pagevec_count(pvec));
1097	pagevec_reinit(pvec);
1098}
 
1099EXPORT_SYMBOL(__pagevec_release);
1100
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1101/**
1102 * folio_batch_remove_exceptionals() - Prune non-folios from a batch.
1103 * @fbatch: The batch to prune
 
 
 
 
 
 
 
1104 *
1105 * find_get_entries() fills a batch with both folios and shadow/swap/DAX
1106 * entries.  This function prunes all the non-folio entries from @fbatch
1107 * without leaving holes, so that it can be passed on to folio-only batch
1108 * operations.
1109 */
1110void folio_batch_remove_exceptionals(struct folio_batch *fbatch)
 
1111{
1112	unsigned int i, j;
 
 
1113
1114	for (i = 0, j = 0; i < folio_batch_count(fbatch); i++) {
1115		struct folio *folio = fbatch->folios[i];
1116		if (!xa_is_value(folio))
1117			fbatch->folios[j++] = folio;
1118	}
1119	fbatch->nr = j;
1120}
1121
1122unsigned pagevec_lookup_range_tag(struct pagevec *pvec,
1123		struct address_space *mapping, pgoff_t *index, pgoff_t end,
1124		xa_mark_t tag)
1125{
1126	pvec->nr = find_get_pages_range_tag(mapping, index, end, tag,
1127					PAGEVEC_SIZE, pvec->pages);
1128	return pagevec_count(pvec);
1129}
1130EXPORT_SYMBOL(pagevec_lookup_range_tag);
 
1131
1132/*
1133 * Perform any setup for the swap system
1134 */
1135void __init swap_setup(void)
1136{
1137	unsigned long megs = totalram_pages() >> (20 - PAGE_SHIFT);
 
 
 
 
1138
1139	/* Use a smaller cluster for small-memory machines */
1140	if (megs < 16)
1141		page_cluster = 2;
1142	else
1143		page_cluster = 3;
1144	/*
1145	 * Right now other parts of the system means that we
1146	 * _really_ don't want to cluster much more
1147	 */
1148}