mm: add get_kernel_page[s] for pinning of kernel addresses for I/O
[linux-3.10.git] / mm / swap.c
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/export.h>
25 #include <linux/mm_inline.h>
26 #include <linux/percpu_counter.h>
27 #include <linux/percpu.h>
28 #include <linux/cpu.h>
29 #include <linux/notifier.h>
30 #include <linux/backing-dev.h>
31 #include <linux/memcontrol.h>
32 #include <linux/gfp.h>
33
34 #include "internal.h"
35
36 /* How many pages do we try to swap or page in/out together? */
37 int page_cluster;
38
39 static DEFINE_PER_CPU(struct pagevec[NR_LRU_LISTS], lru_add_pvecs);
40 static DEFINE_PER_CPU(struct pagevec, lru_rotate_pvecs);
41 static DEFINE_PER_CPU(struct pagevec, lru_deactivate_pvecs);
42
43 /*
44  * This path almost never happens for VM activity - pages are normally
45  * freed via pagevecs.  But it gets used by networking.
46  */
47 static void __page_cache_release(struct page *page)
48 {
49         if (PageLRU(page)) {
50                 struct zone *zone = page_zone(page);
51                 struct lruvec *lruvec;
52                 unsigned long flags;
53
54                 spin_lock_irqsave(&zone->lru_lock, flags);
55                 lruvec = mem_cgroup_page_lruvec(page, zone);
56                 VM_BUG_ON(!PageLRU(page));
57                 __ClearPageLRU(page);
58                 del_page_from_lru_list(page, lruvec, page_off_lru(page));
59                 spin_unlock_irqrestore(&zone->lru_lock, flags);
60         }
61 }
62
63 static void __put_single_page(struct page *page)
64 {
65         __page_cache_release(page);
66         free_hot_cold_page(page, 0);
67 }
68
69 static void __put_compound_page(struct page *page)
70 {
71         compound_page_dtor *dtor;
72
73         __page_cache_release(page);
74         dtor = get_compound_page_dtor(page);
75         (*dtor)(page);
76 }
77
78 static void put_compound_page(struct page *page)
79 {
80         if (unlikely(PageTail(page))) {
81                 /* __split_huge_page_refcount can run under us */
82                 struct page *page_head = compound_trans_head(page);
83
84                 if (likely(page != page_head &&
85                            get_page_unless_zero(page_head))) {
86                         unsigned long flags;
87
88                         /*
89                          * THP can not break up slab pages so avoid taking
90                          * compound_lock().  Slab performs non-atomic bit ops
91                          * on page->flags for better performance.  In particular
92                          * slab_unlock() in slub used to be a hot path.  It is
93                          * still hot on arches that do not support
94                          * this_cpu_cmpxchg_double().
95                          */
96                         if (PageSlab(page_head)) {
97                                 if (PageTail(page)) {
98                                         if (put_page_testzero(page_head))
99                                                 VM_BUG_ON(1);
100
101                                         atomic_dec(&page->_mapcount);
102                                         goto skip_lock_tail;
103                                 } else
104                                         goto skip_lock;
105                         }
106                         /*
107                          * page_head wasn't a dangling pointer but it
108                          * may not be a head page anymore by the time
109                          * we obtain the lock. That is ok as long as it
110                          * can't be freed from under us.
111                          */
112                         flags = compound_lock_irqsave(page_head);
113                         if (unlikely(!PageTail(page))) {
114                                 /* __split_huge_page_refcount run before us */
115                                 compound_unlock_irqrestore(page_head, flags);
116 skip_lock:
117                                 if (put_page_testzero(page_head))
118                                         __put_single_page(page_head);
119 out_put_single:
120                                 if (put_page_testzero(page))
121                                         __put_single_page(page);
122                                 return;
123                         }
124                         VM_BUG_ON(page_head != page->first_page);
125                         /*
126                          * We can release the refcount taken by
127                          * get_page_unless_zero() now that
128                          * __split_huge_page_refcount() is blocked on
129                          * the compound_lock.
130                          */
131                         if (put_page_testzero(page_head))
132                                 VM_BUG_ON(1);
133                         /* __split_huge_page_refcount will wait now */
134                         VM_BUG_ON(page_mapcount(page) <= 0);
135                         atomic_dec(&page->_mapcount);
136                         VM_BUG_ON(atomic_read(&page_head->_count) <= 0);
137                         VM_BUG_ON(atomic_read(&page->_count) != 0);
138                         compound_unlock_irqrestore(page_head, flags);
139
140 skip_lock_tail:
141                         if (put_page_testzero(page_head)) {
142                                 if (PageHead(page_head))
143                                         __put_compound_page(page_head);
144                                 else
145                                         __put_single_page(page_head);
146                         }
147                 } else {
148                         /* page_head is a dangling pointer */
149                         VM_BUG_ON(PageTail(page));
150                         goto out_put_single;
151                 }
152         } else if (put_page_testzero(page)) {
153                 if (PageHead(page))
154                         __put_compound_page(page);
155                 else
156                         __put_single_page(page);
157         }
158 }
159
160 void put_page(struct page *page)
161 {
162         if (unlikely(PageCompound(page)))
163                 put_compound_page(page);
164         else if (put_page_testzero(page))
165                 __put_single_page(page);
166 }
167 EXPORT_SYMBOL(put_page);
168
169 /*
170  * This function is exported but must not be called by anything other
171  * than get_page(). It implements the slow path of get_page().
172  */
173 bool __get_page_tail(struct page *page)
174 {
175         /*
176          * This takes care of get_page() if run on a tail page
177          * returned by one of the get_user_pages/follow_page variants.
178          * get_user_pages/follow_page itself doesn't need the compound
179          * lock because it runs __get_page_tail_foll() under the
180          * proper PT lock that already serializes against
181          * split_huge_page().
182          */
183         unsigned long flags;
184         bool got = false;
185         struct page *page_head = compound_trans_head(page);
186
187         if (likely(page != page_head && get_page_unless_zero(page_head))) {
188
189                 /* Ref to put_compound_page() comment. */
190                 if (PageSlab(page_head)) {
191                         if (likely(PageTail(page))) {
192                                 __get_page_tail_foll(page, false);
193                                 return true;
194                         } else {
195                                 put_page(page_head);
196                                 return false;
197                         }
198                 }
199
200                 /*
201                  * page_head wasn't a dangling pointer but it
202                  * may not be a head page anymore by the time
203                  * we obtain the lock. That is ok as long as it
204                  * can't be freed from under us.
205                  */
206                 flags = compound_lock_irqsave(page_head);
207                 /* here __split_huge_page_refcount won't run anymore */
208                 if (likely(PageTail(page))) {
209                         __get_page_tail_foll(page, false);
210                         got = true;
211                 }
212                 compound_unlock_irqrestore(page_head, flags);
213                 if (unlikely(!got))
214                         put_page(page_head);
215         }
216         return got;
217 }
218 EXPORT_SYMBOL(__get_page_tail);
219
220 /**
221  * put_pages_list() - release a list of pages
222  * @pages: list of pages threaded on page->lru
223  *
224  * Release a list of pages which are strung together on page.lru.  Currently
225  * used by read_cache_pages() and related error recovery code.
226  */
227 void put_pages_list(struct list_head *pages)
228 {
229         while (!list_empty(pages)) {
230                 struct page *victim;
231
232                 victim = list_entry(pages->prev, struct page, lru);
233                 list_del(&victim->lru);
234                 page_cache_release(victim);
235         }
236 }
237 EXPORT_SYMBOL(put_pages_list);
238
239 /*
240  * get_kernel_pages() - pin kernel pages in memory
241  * @kiov:       An array of struct kvec structures
242  * @nr_segs:    number of segments to pin
243  * @write:      pinning for read/write, currently ignored
244  * @pages:      array that receives pointers to the pages pinned.
245  *              Should be at least nr_segs long.
246  *
247  * Returns number of pages pinned. This may be fewer than the number
248  * requested. If nr_pages is 0 or negative, returns 0. If no pages
249  * were pinned, returns -errno. Each page returned must be released
250  * with a put_page() call when it is finished with.
251  */
252 int get_kernel_pages(const struct kvec *kiov, int nr_segs, int write,
253                 struct page **pages)
254 {
255         int seg;
256
257         for (seg = 0; seg < nr_segs; seg++) {
258                 if (WARN_ON(kiov[seg].iov_len != PAGE_SIZE))
259                         return seg;
260
261                 /* virt_to_page sanity checks the PFN */
262                 pages[seg] = virt_to_page(kiov[seg].iov_base);
263                 page_cache_get(pages[seg]);
264         }
265
266         return seg;
267 }
268 EXPORT_SYMBOL_GPL(get_kernel_pages);
269
270 /*
271  * get_kernel_page() - pin a kernel page in memory
272  * @start:      starting kernel address
273  * @write:      pinning for read/write, currently ignored
274  * @pages:      array that receives pointer to the page pinned.
275  *              Must be at least nr_segs long.
276  *
277  * Returns 1 if page is pinned. If the page was not pinned, returns
278  * -errno. The page returned must be released with a put_page() call
279  * when it is finished with.
280  */
281 int get_kernel_page(unsigned long start, int write, struct page **pages)
282 {
283         const struct kvec kiov = {
284                 .iov_base = (void *)start,
285                 .iov_len = PAGE_SIZE
286         };
287
288         return get_kernel_pages(&kiov, 1, write, pages);
289 }
290 EXPORT_SYMBOL_GPL(get_kernel_page);
291
292 static void pagevec_lru_move_fn(struct pagevec *pvec,
293         void (*move_fn)(struct page *page, struct lruvec *lruvec, void *arg),
294         void *arg)
295 {
296         int i;
297         struct zone *zone = NULL;
298         struct lruvec *lruvec;
299         unsigned long flags = 0;
300
301         for (i = 0; i < pagevec_count(pvec); i++) {
302                 struct page *page = pvec->pages[i];
303                 struct zone *pagezone = page_zone(page);
304
305                 if (pagezone != zone) {
306                         if (zone)
307                                 spin_unlock_irqrestore(&zone->lru_lock, flags);
308                         zone = pagezone;
309                         spin_lock_irqsave(&zone->lru_lock, flags);
310                 }
311
312                 lruvec = mem_cgroup_page_lruvec(page, zone);
313                 (*move_fn)(page, lruvec, arg);
314         }
315         if (zone)
316                 spin_unlock_irqrestore(&zone->lru_lock, flags);
317         release_pages(pvec->pages, pvec->nr, pvec->cold);
318         pagevec_reinit(pvec);
319 }
320
321 static void pagevec_move_tail_fn(struct page *page, struct lruvec *lruvec,
322                                  void *arg)
323 {
324         int *pgmoved = arg;
325
326         if (PageLRU(page) && !PageActive(page) && !PageUnevictable(page)) {
327                 enum lru_list lru = page_lru_base_type(page);
328                 list_move_tail(&page->lru, &lruvec->lists[lru]);
329                 (*pgmoved)++;
330         }
331 }
332
333 /*
334  * pagevec_move_tail() must be called with IRQ disabled.
335  * Otherwise this may cause nasty races.
336  */
337 static void pagevec_move_tail(struct pagevec *pvec)
338 {
339         int pgmoved = 0;
340
341         pagevec_lru_move_fn(pvec, pagevec_move_tail_fn, &pgmoved);
342         __count_vm_events(PGROTATED, pgmoved);
343 }
344
345 /*
346  * Writeback is about to end against a page which has been marked for immediate
347  * reclaim.  If it still appears to be reclaimable, move it to the tail of the
348  * inactive list.
349  */
350 void rotate_reclaimable_page(struct page *page)
351 {
352         if (!PageLocked(page) && !PageDirty(page) && !PageActive(page) &&
353             !PageUnevictable(page) && PageLRU(page)) {
354                 struct pagevec *pvec;
355                 unsigned long flags;
356
357                 page_cache_get(page);
358                 local_irq_save(flags);
359                 pvec = &__get_cpu_var(lru_rotate_pvecs);
360                 if (!pagevec_add(pvec, page))
361                         pagevec_move_tail(pvec);
362                 local_irq_restore(flags);
363         }
364 }
365
366 static void update_page_reclaim_stat(struct lruvec *lruvec,
367                                      int file, int rotated)
368 {
369         struct zone_reclaim_stat *reclaim_stat = &lruvec->reclaim_stat;
370
371         reclaim_stat->recent_scanned[file]++;
372         if (rotated)
373                 reclaim_stat->recent_rotated[file]++;
374 }
375
376 static void __activate_page(struct page *page, struct lruvec *lruvec,
377                             void *arg)
378 {
379         if (PageLRU(page) && !PageActive(page) && !PageUnevictable(page)) {
380                 int file = page_is_file_cache(page);
381                 int lru = page_lru_base_type(page);
382
383                 del_page_from_lru_list(page, lruvec, lru);
384                 SetPageActive(page);
385                 lru += LRU_ACTIVE;
386                 add_page_to_lru_list(page, lruvec, lru);
387
388                 __count_vm_event(PGACTIVATE);
389                 update_page_reclaim_stat(lruvec, file, 1);
390         }
391 }
392
393 #ifdef CONFIG_SMP
394 static DEFINE_PER_CPU(struct pagevec, activate_page_pvecs);
395
396 static void activate_page_drain(int cpu)
397 {
398         struct pagevec *pvec = &per_cpu(activate_page_pvecs, cpu);
399
400         if (pagevec_count(pvec))
401                 pagevec_lru_move_fn(pvec, __activate_page, NULL);
402 }
403
404 void activate_page(struct page *page)
405 {
406         if (PageLRU(page) && !PageActive(page) && !PageUnevictable(page)) {
407                 struct pagevec *pvec = &get_cpu_var(activate_page_pvecs);
408
409                 page_cache_get(page);
410                 if (!pagevec_add(pvec, page))
411                         pagevec_lru_move_fn(pvec, __activate_page, NULL);
412                 put_cpu_var(activate_page_pvecs);
413         }
414 }
415
416 #else
417 static inline void activate_page_drain(int cpu)
418 {
419 }
420
421 void activate_page(struct page *page)
422 {
423         struct zone *zone = page_zone(page);
424
425         spin_lock_irq(&zone->lru_lock);
426         __activate_page(page, mem_cgroup_page_lruvec(page, zone), NULL);
427         spin_unlock_irq(&zone->lru_lock);
428 }
429 #endif
430
431 /*
432  * Mark a page as having seen activity.
433  *
434  * inactive,unreferenced        ->      inactive,referenced
435  * inactive,referenced          ->      active,unreferenced
436  * active,unreferenced          ->      active,referenced
437  */
438 void mark_page_accessed(struct page *page)
439 {
440         if (!PageActive(page) && !PageUnevictable(page) &&
441                         PageReferenced(page) && PageLRU(page)) {
442                 activate_page(page);
443                 ClearPageReferenced(page);
444         } else if (!PageReferenced(page)) {
445                 SetPageReferenced(page);
446         }
447 }
448 EXPORT_SYMBOL(mark_page_accessed);
449
450 void __lru_cache_add(struct page *page, enum lru_list lru)
451 {
452         struct pagevec *pvec = &get_cpu_var(lru_add_pvecs)[lru];
453
454         page_cache_get(page);
455         if (!pagevec_add(pvec, page))
456                 __pagevec_lru_add(pvec, lru);
457         put_cpu_var(lru_add_pvecs);
458 }
459 EXPORT_SYMBOL(__lru_cache_add);
460
461 /**
462  * lru_cache_add_lru - add a page to a page list
463  * @page: the page to be added to the LRU.
464  * @lru: the LRU list to which the page is added.
465  */
466 void lru_cache_add_lru(struct page *page, enum lru_list lru)
467 {
468         if (PageActive(page)) {
469                 VM_BUG_ON(PageUnevictable(page));
470                 ClearPageActive(page);
471         } else if (PageUnevictable(page)) {
472                 VM_BUG_ON(PageActive(page));
473                 ClearPageUnevictable(page);
474         }
475
476         VM_BUG_ON(PageLRU(page) || PageActive(page) || PageUnevictable(page));
477         __lru_cache_add(page, lru);
478 }
479
480 /**
481  * add_page_to_unevictable_list - add a page to the unevictable list
482  * @page:  the page to be added to the unevictable list
483  *
484  * Add page directly to its zone's unevictable list.  To avoid races with
485  * tasks that might be making the page evictable, through eg. munlock,
486  * munmap or exit, while it's not on the lru, we want to add the page
487  * while it's locked or otherwise "invisible" to other tasks.  This is
488  * difficult to do when using the pagevec cache, so bypass that.
489  */
490 void add_page_to_unevictable_list(struct page *page)
491 {
492         struct zone *zone = page_zone(page);
493         struct lruvec *lruvec;
494
495         spin_lock_irq(&zone->lru_lock);
496         lruvec = mem_cgroup_page_lruvec(page, zone);
497         SetPageUnevictable(page);
498         SetPageLRU(page);
499         add_page_to_lru_list(page, lruvec, LRU_UNEVICTABLE);
500         spin_unlock_irq(&zone->lru_lock);
501 }
502
503 /*
504  * If the page can not be invalidated, it is moved to the
505  * inactive list to speed up its reclaim.  It is moved to the
506  * head of the list, rather than the tail, to give the flusher
507  * threads some time to write it out, as this is much more
508  * effective than the single-page writeout from reclaim.
509  *
510  * If the page isn't page_mapped and dirty/writeback, the page
511  * could reclaim asap using PG_reclaim.
512  *
513  * 1. active, mapped page -> none
514  * 2. active, dirty/writeback page -> inactive, head, PG_reclaim
515  * 3. inactive, mapped page -> none
516  * 4. inactive, dirty/writeback page -> inactive, head, PG_reclaim
517  * 5. inactive, clean -> inactive, tail
518  * 6. Others -> none
519  *
520  * In 4, why it moves inactive's head, the VM expects the page would
521  * be write it out by flusher threads as this is much more effective
522  * than the single-page writeout from reclaim.
523  */
524 static void lru_deactivate_fn(struct page *page, struct lruvec *lruvec,
525                               void *arg)
526 {
527         int lru, file;
528         bool active;
529
530         if (!PageLRU(page))
531                 return;
532
533         if (PageUnevictable(page))
534                 return;
535
536         /* Some processes are using the page */
537         if (page_mapped(page))
538                 return;
539
540         active = PageActive(page);
541         file = page_is_file_cache(page);
542         lru = page_lru_base_type(page);
543
544         del_page_from_lru_list(page, lruvec, lru + active);
545         ClearPageActive(page);
546         ClearPageReferenced(page);
547         add_page_to_lru_list(page, lruvec, lru);
548
549         if (PageWriteback(page) || PageDirty(page)) {
550                 /*
551                  * PG_reclaim could be raced with end_page_writeback
552                  * It can make readahead confusing.  But race window
553                  * is _really_ small and  it's non-critical problem.
554                  */
555                 SetPageReclaim(page);
556         } else {
557                 /*
558                  * The page's writeback ends up during pagevec
559                  * We moves tha page into tail of inactive.
560                  */
561                 list_move_tail(&page->lru, &lruvec->lists[lru]);
562                 __count_vm_event(PGROTATED);
563         }
564
565         if (active)
566                 __count_vm_event(PGDEACTIVATE);
567         update_page_reclaim_stat(lruvec, file, 0);
568 }
569
570 /*
571  * Drain pages out of the cpu's pagevecs.
572  * Either "cpu" is the current CPU, and preemption has already been
573  * disabled; or "cpu" is being hot-unplugged, and is already dead.
574  */
575 void lru_add_drain_cpu(int cpu)
576 {
577         struct pagevec *pvecs = per_cpu(lru_add_pvecs, cpu);
578         struct pagevec *pvec;
579         int lru;
580
581         for_each_lru(lru) {
582                 pvec = &pvecs[lru - LRU_BASE];
583                 if (pagevec_count(pvec))
584                         __pagevec_lru_add(pvec, lru);
585         }
586
587         pvec = &per_cpu(lru_rotate_pvecs, cpu);
588         if (pagevec_count(pvec)) {
589                 unsigned long flags;
590
591                 /* No harm done if a racing interrupt already did this */
592                 local_irq_save(flags);
593                 pagevec_move_tail(pvec);
594                 local_irq_restore(flags);
595         }
596
597         pvec = &per_cpu(lru_deactivate_pvecs, cpu);
598         if (pagevec_count(pvec))
599                 pagevec_lru_move_fn(pvec, lru_deactivate_fn, NULL);
600
601         activate_page_drain(cpu);
602 }
603
604 /**
605  * deactivate_page - forcefully deactivate a page
606  * @page: page to deactivate
607  *
608  * This function hints the VM that @page is a good reclaim candidate,
609  * for example if its invalidation fails due to the page being dirty
610  * or under writeback.
611  */
612 void deactivate_page(struct page *page)
613 {
614         /*
615          * In a workload with many unevictable page such as mprotect, unevictable
616          * page deactivation for accelerating reclaim is pointless.
617          */
618         if (PageUnevictable(page))
619                 return;
620
621         if (likely(get_page_unless_zero(page))) {
622                 struct pagevec *pvec = &get_cpu_var(lru_deactivate_pvecs);
623
624                 if (!pagevec_add(pvec, page))
625                         pagevec_lru_move_fn(pvec, lru_deactivate_fn, NULL);
626                 put_cpu_var(lru_deactivate_pvecs);
627         }
628 }
629
630 void lru_add_drain(void)
631 {
632         lru_add_drain_cpu(get_cpu());
633         put_cpu();
634 }
635
636 static void lru_add_drain_per_cpu(struct work_struct *dummy)
637 {
638         lru_add_drain();
639 }
640
641 /*
642  * Returns 0 for success
643  */
644 int lru_add_drain_all(void)
645 {
646         return schedule_on_each_cpu(lru_add_drain_per_cpu);
647 }
648
649 /*
650  * Batched page_cache_release().  Decrement the reference count on all the
651  * passed pages.  If it fell to zero then remove the page from the LRU and
652  * free it.
653  *
654  * Avoid taking zone->lru_lock if possible, but if it is taken, retain it
655  * for the remainder of the operation.
656  *
657  * The locking in this function is against shrink_inactive_list(): we recheck
658  * the page count inside the lock to see whether shrink_inactive_list()
659  * grabbed the page via the LRU.  If it did, give up: shrink_inactive_list()
660  * will free it.
661  */
662 void release_pages(struct page **pages, int nr, int cold)
663 {
664         int i;
665         LIST_HEAD(pages_to_free);
666         struct zone *zone = NULL;
667         struct lruvec *lruvec;
668         unsigned long uninitialized_var(flags);
669
670         for (i = 0; i < nr; i++) {
671                 struct page *page = pages[i];
672
673                 if (unlikely(PageCompound(page))) {
674                         if (zone) {
675                                 spin_unlock_irqrestore(&zone->lru_lock, flags);
676                                 zone = NULL;
677                         }
678                         put_compound_page(page);
679                         continue;
680                 }
681
682                 if (!put_page_testzero(page))
683                         continue;
684
685                 if (PageLRU(page)) {
686                         struct zone *pagezone = page_zone(page);
687
688                         if (pagezone != zone) {
689                                 if (zone)
690                                         spin_unlock_irqrestore(&zone->lru_lock,
691                                                                         flags);
692                                 zone = pagezone;
693                                 spin_lock_irqsave(&zone->lru_lock, flags);
694                         }
695
696                         lruvec = mem_cgroup_page_lruvec(page, zone);
697                         VM_BUG_ON(!PageLRU(page));
698                         __ClearPageLRU(page);
699                         del_page_from_lru_list(page, lruvec, page_off_lru(page));
700                 }
701
702                 list_add(&page->lru, &pages_to_free);
703         }
704         if (zone)
705                 spin_unlock_irqrestore(&zone->lru_lock, flags);
706
707         free_hot_cold_page_list(&pages_to_free, cold);
708 }
709 EXPORT_SYMBOL(release_pages);
710
711 /*
712  * The pages which we're about to release may be in the deferred lru-addition
713  * queues.  That would prevent them from really being freed right now.  That's
714  * OK from a correctness point of view but is inefficient - those pages may be
715  * cache-warm and we want to give them back to the page allocator ASAP.
716  *
717  * So __pagevec_release() will drain those queues here.  __pagevec_lru_add()
718  * and __pagevec_lru_add_active() call release_pages() directly to avoid
719  * mutual recursion.
720  */
721 void __pagevec_release(struct pagevec *pvec)
722 {
723         lru_add_drain();
724         release_pages(pvec->pages, pagevec_count(pvec), pvec->cold);
725         pagevec_reinit(pvec);
726 }
727 EXPORT_SYMBOL(__pagevec_release);
728
729 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
730 /* used by __split_huge_page_refcount() */
731 void lru_add_page_tail(struct page *page, struct page *page_tail,
732                        struct lruvec *lruvec)
733 {
734         int uninitialized_var(active);
735         enum lru_list lru;
736         const int file = 0;
737
738         VM_BUG_ON(!PageHead(page));
739         VM_BUG_ON(PageCompound(page_tail));
740         VM_BUG_ON(PageLRU(page_tail));
741         VM_BUG_ON(NR_CPUS != 1 &&
742                   !spin_is_locked(&lruvec_zone(lruvec)->lru_lock));
743
744         SetPageLRU(page_tail);
745
746         if (page_evictable(page_tail, NULL)) {
747                 if (PageActive(page)) {
748                         SetPageActive(page_tail);
749                         active = 1;
750                         lru = LRU_ACTIVE_ANON;
751                 } else {
752                         active = 0;
753                         lru = LRU_INACTIVE_ANON;
754                 }
755         } else {
756                 SetPageUnevictable(page_tail);
757                 lru = LRU_UNEVICTABLE;
758         }
759
760         if (likely(PageLRU(page)))
761                 list_add_tail(&page_tail->lru, &page->lru);
762         else {
763                 struct list_head *list_head;
764                 /*
765                  * Head page has not yet been counted, as an hpage,
766                  * so we must account for each subpage individually.
767                  *
768                  * Use the standard add function to put page_tail on the list,
769                  * but then correct its position so they all end up in order.
770                  */
771                 add_page_to_lru_list(page_tail, lruvec, lru);
772                 list_head = page_tail->lru.prev;
773                 list_move_tail(&page_tail->lru, list_head);
774         }
775
776         if (!PageUnevictable(page))
777                 update_page_reclaim_stat(lruvec, file, active);
778 }
779 #endif /* CONFIG_TRANSPARENT_HUGEPAGE */
780
781 static void __pagevec_lru_add_fn(struct page *page, struct lruvec *lruvec,
782                                  void *arg)
783 {
784         enum lru_list lru = (enum lru_list)arg;
785         int file = is_file_lru(lru);
786         int active = is_active_lru(lru);
787
788         VM_BUG_ON(PageActive(page));
789         VM_BUG_ON(PageUnevictable(page));
790         VM_BUG_ON(PageLRU(page));
791
792         SetPageLRU(page);
793         if (active)
794                 SetPageActive(page);
795         add_page_to_lru_list(page, lruvec, lru);
796         update_page_reclaim_stat(lruvec, file, active);
797 }
798
799 /*
800  * Add the passed pages to the LRU, then drop the caller's refcount
801  * on them.  Reinitialises the caller's pagevec.
802  */
803 void __pagevec_lru_add(struct pagevec *pvec, enum lru_list lru)
804 {
805         VM_BUG_ON(is_unevictable_lru(lru));
806
807         pagevec_lru_move_fn(pvec, __pagevec_lru_add_fn, (void *)lru);
808 }
809 EXPORT_SYMBOL(__pagevec_lru_add);
810
811 /**
812  * pagevec_lookup - gang pagecache lookup
813  * @pvec:       Where the resulting pages are placed
814  * @mapping:    The address_space to search
815  * @start:      The starting page index
816  * @nr_pages:   The maximum number of pages
817  *
818  * pagevec_lookup() will search for and return a group of up to @nr_pages pages
819  * in the mapping.  The pages are placed in @pvec.  pagevec_lookup() takes a
820  * reference against the pages in @pvec.
821  *
822  * The search returns a group of mapping-contiguous pages with ascending
823  * indexes.  There may be holes in the indices due to not-present pages.
824  *
825  * pagevec_lookup() returns the number of pages which were found.
826  */
827 unsigned pagevec_lookup(struct pagevec *pvec, struct address_space *mapping,
828                 pgoff_t start, unsigned nr_pages)
829 {
830         pvec->nr = find_get_pages(mapping, start, nr_pages, pvec->pages);
831         return pagevec_count(pvec);
832 }
833 EXPORT_SYMBOL(pagevec_lookup);
834
835 unsigned pagevec_lookup_tag(struct pagevec *pvec, struct address_space *mapping,
836                 pgoff_t *index, int tag, unsigned nr_pages)
837 {
838         pvec->nr = find_get_pages_tag(mapping, index, tag,
839                                         nr_pages, pvec->pages);
840         return pagevec_count(pvec);
841 }
842 EXPORT_SYMBOL(pagevec_lookup_tag);
843
844 /*
845  * Perform any setup for the swap system
846  */
847 void __init swap_setup(void)
848 {
849         unsigned long megs = totalram_pages >> (20 - PAGE_SHIFT);
850
851 #ifdef CONFIG_SWAP
852         bdi_init(swapper_space.backing_dev_info);
853 #endif
854
855         /* Use a smaller cluster for small-memory machines */
856         if (megs < 16)
857                 page_cluster = 2;
858         else
859                 page_cluster = 3;
860         /*
861          * Right now other parts of the system means that we
862          * _really_ don't want to cluster much more
863          */
864 }