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9
10#include <linux/mm.h>
11#include <linux/gfp.h>
12#include <linux/kernel_stat.h>
13#include <linux/swap.h>
14#include <linux/swapops.h>
15#include <linux/init.h>
16#include <linux/pagemap.h>
17#include <linux/backing-dev.h>
18#include <linux/blkdev.h>
19#include <linux/pagevec.h>
20#include <linux/migrate.h>
21#include <linux/vmalloc.h>
22#include <linux/swap_slots.h>
23#include <linux/huge_mm.h>
24
25#include <asm/pgtable.h>
26
27
28
29
30
31static const struct address_space_operations swap_aops = {
32 .writepage = swap_writepage,
33 .set_page_dirty = swap_set_page_dirty,
34#ifdef CONFIG_MIGRATION
35 .migratepage = migrate_page,
36#endif
37};
38
39struct address_space *swapper_spaces[MAX_SWAPFILES] __read_mostly;
40static unsigned int nr_swapper_spaces[MAX_SWAPFILES] __read_mostly;
41static bool enable_vma_readahead __read_mostly = true;
42
43#define SWAP_RA_WIN_SHIFT (PAGE_SHIFT / 2)
44#define SWAP_RA_HITS_MASK ((1UL << SWAP_RA_WIN_SHIFT) - 1)
45#define SWAP_RA_HITS_MAX SWAP_RA_HITS_MASK
46#define SWAP_RA_WIN_MASK (~PAGE_MASK & ~SWAP_RA_HITS_MASK)
47
48#define SWAP_RA_HITS(v) ((v) & SWAP_RA_HITS_MASK)
49#define SWAP_RA_WIN(v) (((v) & SWAP_RA_WIN_MASK) >> SWAP_RA_WIN_SHIFT)
50#define SWAP_RA_ADDR(v) ((v) & PAGE_MASK)
51
52#define SWAP_RA_VAL(addr, win, hits) \
53 (((addr) & PAGE_MASK) | \
54 (((win) << SWAP_RA_WIN_SHIFT) & SWAP_RA_WIN_MASK) | \
55 ((hits) & SWAP_RA_HITS_MASK))
56
57
58#define GET_SWAP_RA_VAL(vma) \
59 (atomic_long_read(&(vma)->swap_readahead_info) ? : 4)
60
61#define INC_CACHE_INFO(x) do { swap_cache_info.x++; } while (0)
62#define ADD_CACHE_INFO(x, nr) do { swap_cache_info.x += (nr); } while (0)
63
64static struct {
65 unsigned long add_total;
66 unsigned long del_total;
67 unsigned long find_success;
68 unsigned long find_total;
69} swap_cache_info;
70
71unsigned long total_swapcache_pages(void)
72{
73 unsigned int i, j, nr;
74 unsigned long ret = 0;
75 struct address_space *spaces;
76
77 rcu_read_lock();
78 for (i = 0; i < MAX_SWAPFILES; i++) {
79
80
81
82
83
84
85 nr = nr_swapper_spaces[i];
86 spaces = rcu_dereference(swapper_spaces[i]);
87 if (!nr || !spaces)
88 continue;
89 for (j = 0; j < nr; j++)
90 ret += spaces[j].nrpages;
91 }
92 rcu_read_unlock();
93 return ret;
94}
95
96static atomic_t swapin_readahead_hits = ATOMIC_INIT(4);
97
98void show_swap_cache_info(void)
99{
100 printk("%lu pages in swap cache\n", total_swapcache_pages());
101 printk("Swap cache stats: add %lu, delete %lu, find %lu/%lu\n",
102 swap_cache_info.add_total, swap_cache_info.del_total,
103 swap_cache_info.find_success, swap_cache_info.find_total);
104 printk("Free swap = %ldkB\n",
105 get_nr_swap_pages() << (PAGE_SHIFT - 10));
106 printk("Total swap = %lukB\n", total_swap_pages << (PAGE_SHIFT - 10));
107}
108
109
110
111
112
113int __add_to_swap_cache(struct page *page, swp_entry_t entry)
114{
115 int error, i, nr = hpage_nr_pages(page);
116 struct address_space *address_space;
117 pgoff_t idx = swp_offset(entry);
118
119 VM_BUG_ON_PAGE(!PageLocked(page), page);
120 VM_BUG_ON_PAGE(PageSwapCache(page), page);
121 VM_BUG_ON_PAGE(!PageSwapBacked(page), page);
122
123 page_ref_add(page, nr);
124 SetPageSwapCache(page);
125
126 address_space = swap_address_space(entry);
127 xa_lock_irq(&address_space->i_pages);
128 for (i = 0; i < nr; i++) {
129 set_page_private(page + i, entry.val + i);
130 error = radix_tree_insert(&address_space->i_pages,
131 idx + i, page + i);
132 if (unlikely(error))
133 break;
134 }
135 if (likely(!error)) {
136 address_space->nrpages += nr;
137 __mod_node_page_state(page_pgdat(page), NR_FILE_PAGES, nr);
138 ADD_CACHE_INFO(add_total, nr);
139 } else {
140
141
142
143
144
145 VM_BUG_ON(error == -EEXIST);
146 set_page_private(page + i, 0UL);
147 while (i--) {
148 radix_tree_delete(&address_space->i_pages, idx + i);
149 set_page_private(page + i, 0UL);
150 }
151 ClearPageSwapCache(page);
152 page_ref_sub(page, nr);
153 }
154 xa_unlock_irq(&address_space->i_pages);
155
156 return error;
157}
158
159
160int add_to_swap_cache(struct page *page, swp_entry_t entry, gfp_t gfp_mask)
161{
162 int error;
163
164 error = radix_tree_maybe_preload_order(gfp_mask, compound_order(page));
165 if (!error) {
166 error = __add_to_swap_cache(page, entry);
167 radix_tree_preload_end();
168 }
169 return error;
170}
171
172
173
174
175
176void __delete_from_swap_cache(struct page *page)
177{
178 struct address_space *address_space;
179 int i, nr = hpage_nr_pages(page);
180 swp_entry_t entry;
181 pgoff_t idx;
182
183 VM_BUG_ON_PAGE(!PageLocked(page), page);
184 VM_BUG_ON_PAGE(!PageSwapCache(page), page);
185 VM_BUG_ON_PAGE(PageWriteback(page), page);
186
187 entry.val = page_private(page);
188 address_space = swap_address_space(entry);
189 idx = swp_offset(entry);
190 for (i = 0; i < nr; i++) {
191 radix_tree_delete(&address_space->i_pages, idx + i);
192 set_page_private(page + i, 0);
193 }
194 ClearPageSwapCache(page);
195 address_space->nrpages -= nr;
196 __mod_node_page_state(page_pgdat(page), NR_FILE_PAGES, -nr);
197 ADD_CACHE_INFO(del_total, nr);
198}
199
200
201
202
203
204
205
206
207int add_to_swap(struct page *page)
208{
209 swp_entry_t entry;
210 int err;
211
212 VM_BUG_ON_PAGE(!PageLocked(page), page);
213 VM_BUG_ON_PAGE(!PageUptodate(page), page);
214
215 entry = get_swap_page(page);
216 if (!entry.val)
217 return 0;
218
219
220
221
222
223
224
225
226
227
228
229
230 err = add_to_swap_cache(page, entry,
231 __GFP_HIGH|__GFP_NOMEMALLOC|__GFP_NOWARN);
232
233 if (err)
234
235
236
237
238 goto fail;
239
240
241
242
243
244
245
246
247
248
249 set_page_dirty(page);
250
251 return 1;
252
253fail:
254 put_swap_page(page, entry);
255 return 0;
256}
257
258
259
260
261
262
263
264void delete_from_swap_cache(struct page *page)
265{
266 swp_entry_t entry;
267 struct address_space *address_space;
268
269 entry.val = page_private(page);
270
271 address_space = swap_address_space(entry);
272 xa_lock_irq(&address_space->i_pages);
273 __delete_from_swap_cache(page);
274 xa_unlock_irq(&address_space->i_pages);
275
276 put_swap_page(page, entry);
277 page_ref_sub(page, hpage_nr_pages(page));
278}
279
280
281
282
283
284
285
286
287
288static inline void free_swap_cache(struct page *page)
289{
290 if (PageSwapCache(page) && !page_mapped(page) && trylock_page(page)) {
291 try_to_free_swap(page);
292 unlock_page(page);
293 }
294}
295
296
297
298
299
300void free_page_and_swap_cache(struct page *page)
301{
302 free_swap_cache(page);
303 if (!is_huge_zero_page(page))
304 put_page(page);
305}
306
307
308
309
310
311void free_pages_and_swap_cache(struct page **pages, int nr)
312{
313 struct page **pagep = pages;
314 int i;
315
316 lru_add_drain();
317 for (i = 0; i < nr; i++)
318 free_swap_cache(pagep[i]);
319 release_pages(pagep, nr);
320}
321
322static inline bool swap_use_vma_readahead(void)
323{
324 return READ_ONCE(enable_vma_readahead) && !atomic_read(&nr_rotate_swap);
325}
326
327
328
329
330
331
332
333struct page *lookup_swap_cache(swp_entry_t entry, struct vm_area_struct *vma,
334 unsigned long addr)
335{
336 struct page *page;
337
338 page = find_get_page(swap_address_space(entry), swp_offset(entry));
339
340 INC_CACHE_INFO(find_total);
341 if (page) {
342 bool vma_ra = swap_use_vma_readahead();
343 bool readahead;
344
345 INC_CACHE_INFO(find_success);
346
347
348
349
350 if (unlikely(PageTransCompound(page)))
351 return page;
352
353 readahead = TestClearPageReadahead(page);
354 if (vma && vma_ra) {
355 unsigned long ra_val;
356 int win, hits;
357
358 ra_val = GET_SWAP_RA_VAL(vma);
359 win = SWAP_RA_WIN(ra_val);
360 hits = SWAP_RA_HITS(ra_val);
361 if (readahead)
362 hits = min_t(int, hits + 1, SWAP_RA_HITS_MAX);
363 atomic_long_set(&vma->swap_readahead_info,
364 SWAP_RA_VAL(addr, win, hits));
365 }
366
367 if (readahead) {
368 count_vm_event(SWAP_RA_HIT);
369 if (!vma || !vma_ra)
370 atomic_inc(&swapin_readahead_hits);
371 }
372 }
373
374 return page;
375}
376
377struct page *__read_swap_cache_async(swp_entry_t entry, gfp_t gfp_mask,
378 struct vm_area_struct *vma, unsigned long addr,
379 bool *new_page_allocated)
380{
381 struct page *found_page, *new_page = NULL;
382 struct address_space *swapper_space = swap_address_space(entry);
383 int err;
384 *new_page_allocated = false;
385
386 do {
387
388
389
390
391
392 found_page = find_get_page(swapper_space, swp_offset(entry));
393 if (found_page)
394 break;
395
396
397
398
399
400
401
402
403
404 if (!__swp_swapcount(entry) && swap_slot_cache_enabled)
405 break;
406
407
408
409
410 if (!new_page) {
411 new_page = alloc_page_vma(gfp_mask, vma, addr);
412 if (!new_page)
413 break;
414 }
415
416
417
418
419 err = radix_tree_maybe_preload(gfp_mask & GFP_KERNEL);
420 if (err)
421 break;
422
423
424
425
426 err = swapcache_prepare(entry);
427 if (err == -EEXIST) {
428 radix_tree_preload_end();
429
430
431
432
433
434 cond_resched();
435 continue;
436 }
437 if (err) {
438 radix_tree_preload_end();
439 break;
440 }
441
442
443 __SetPageLocked(new_page);
444 __SetPageSwapBacked(new_page);
445 err = __add_to_swap_cache(new_page, entry);
446 if (likely(!err)) {
447 radix_tree_preload_end();
448
449
450
451 lru_cache_add_anon(new_page);
452 *new_page_allocated = true;
453 return new_page;
454 }
455 radix_tree_preload_end();
456 __ClearPageLocked(new_page);
457
458
459
460
461 put_swap_page(new_page, entry);
462 } while (err != -ENOMEM);
463
464 if (new_page)
465 put_page(new_page);
466 return found_page;
467}
468
469
470
471
472
473
474
475struct page *read_swap_cache_async(swp_entry_t entry, gfp_t gfp_mask,
476 struct vm_area_struct *vma, unsigned long addr, bool do_poll)
477{
478 bool page_was_allocated;
479 struct page *retpage = __read_swap_cache_async(entry, gfp_mask,
480 vma, addr, &page_was_allocated);
481
482 if (page_was_allocated)
483 swap_readpage(retpage, do_poll);
484
485 return retpage;
486}
487
488static unsigned int __swapin_nr_pages(unsigned long prev_offset,
489 unsigned long offset,
490 int hits,
491 int max_pages,
492 int prev_win)
493{
494 unsigned int pages, last_ra;
495
496
497
498
499
500
501 pages = hits + 2;
502 if (pages == 2) {
503
504
505
506
507
508 if (offset != prev_offset + 1 && offset != prev_offset - 1)
509 pages = 1;
510 } else {
511 unsigned int roundup = 4;
512 while (roundup < pages)
513 roundup <<= 1;
514 pages = roundup;
515 }
516
517 if (pages > max_pages)
518 pages = max_pages;
519
520
521 last_ra = prev_win / 2;
522 if (pages < last_ra)
523 pages = last_ra;
524
525 return pages;
526}
527
528static unsigned long swapin_nr_pages(unsigned long offset)
529{
530 static unsigned long prev_offset;
531 unsigned int hits, pages, max_pages;
532 static atomic_t last_readahead_pages;
533
534 max_pages = 1 << READ_ONCE(page_cluster);
535 if (max_pages <= 1)
536 return 1;
537
538 hits = atomic_xchg(&swapin_readahead_hits, 0);
539 pages = __swapin_nr_pages(prev_offset, offset, hits, max_pages,
540 atomic_read(&last_readahead_pages));
541 if (!hits)
542 prev_offset = offset;
543 atomic_set(&last_readahead_pages, pages);
544
545 return pages;
546}
547
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559
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563
564
565
566struct page *swap_cluster_readahead(swp_entry_t entry, gfp_t gfp_mask,
567 struct vm_fault *vmf)
568{
569 struct page *page;
570 unsigned long entry_offset = swp_offset(entry);
571 unsigned long offset = entry_offset;
572 unsigned long start_offset, end_offset;
573 unsigned long mask;
574 struct swap_info_struct *si = swp_swap_info(entry);
575 struct blk_plug plug;
576 bool do_poll = true, page_allocated;
577 struct vm_area_struct *vma = vmf->vma;
578 unsigned long addr = vmf->address;
579
580 mask = swapin_nr_pages(offset) - 1;
581 if (!mask)
582 goto skip;
583
584 do_poll = false;
585
586 start_offset = offset & ~mask;
587 end_offset = offset | mask;
588 if (!start_offset)
589 start_offset++;
590 if (end_offset >= si->max)
591 end_offset = si->max - 1;
592
593 blk_start_plug(&plug);
594 for (offset = start_offset; offset <= end_offset ; offset++) {
595
596 page = __read_swap_cache_async(
597 swp_entry(swp_type(entry), offset),
598 gfp_mask, vma, addr, &page_allocated);
599 if (!page)
600 continue;
601 if (page_allocated) {
602 swap_readpage(page, false);
603 if (offset != entry_offset) {
604 SetPageReadahead(page);
605 count_vm_event(SWAP_RA);
606 }
607 }
608 put_page(page);
609 }
610 blk_finish_plug(&plug);
611
612 lru_add_drain();
613skip:
614 return read_swap_cache_async(entry, gfp_mask, vma, addr, do_poll);
615}
616
617int init_swap_address_space(unsigned int type, unsigned long nr_pages)
618{
619 struct address_space *spaces, *space;
620 unsigned int i, nr;
621
622 nr = DIV_ROUND_UP(nr_pages, SWAP_ADDRESS_SPACE_PAGES);
623 spaces = kvcalloc(nr, sizeof(struct address_space), GFP_KERNEL);
624 if (!spaces)
625 return -ENOMEM;
626 for (i = 0; i < nr; i++) {
627 space = spaces + i;
628 INIT_RADIX_TREE(&space->i_pages, GFP_ATOMIC|__GFP_NOWARN);
629 atomic_set(&space->i_mmap_writable, 0);
630 space->a_ops = &swap_aops;
631
632 mapping_set_no_writeback_tags(space);
633 }
634 nr_swapper_spaces[type] = nr;
635 rcu_assign_pointer(swapper_spaces[type], spaces);
636
637 return 0;
638}
639
640void exit_swap_address_space(unsigned int type)
641{
642 struct address_space *spaces;
643
644 spaces = swapper_spaces[type];
645 nr_swapper_spaces[type] = 0;
646 rcu_assign_pointer(swapper_spaces[type], NULL);
647 synchronize_rcu();
648 kvfree(spaces);
649}
650
651static inline void swap_ra_clamp_pfn(struct vm_area_struct *vma,
652 unsigned long faddr,
653 unsigned long lpfn,
654 unsigned long rpfn,
655 unsigned long *start,
656 unsigned long *end)
657{
658 *start = max3(lpfn, PFN_DOWN(vma->vm_start),
659 PFN_DOWN(faddr & PMD_MASK));
660 *end = min3(rpfn, PFN_DOWN(vma->vm_end),
661 PFN_DOWN((faddr & PMD_MASK) + PMD_SIZE));
662}
663
664static void swap_ra_info(struct vm_fault *vmf,
665 struct vma_swap_readahead *ra_info)
666{
667 struct vm_area_struct *vma = vmf->vma;
668 unsigned long ra_val;
669 swp_entry_t entry;
670 unsigned long faddr, pfn, fpfn;
671 unsigned long start, end;
672 pte_t *pte, *orig_pte;
673 unsigned int max_win, hits, prev_win, win, left;
674#ifndef CONFIG_64BIT
675 pte_t *tpte;
676#endif
677
678 max_win = 1 << min_t(unsigned int, READ_ONCE(page_cluster),
679 SWAP_RA_ORDER_CEILING);
680 if (max_win == 1) {
681 ra_info->win = 1;
682 return;
683 }
684
685 faddr = vmf->address;
686 orig_pte = pte = pte_offset_map(vmf->pmd, faddr);
687 entry = pte_to_swp_entry(*pte);
688 if ((unlikely(non_swap_entry(entry)))) {
689 pte_unmap(orig_pte);
690 return;
691 }
692
693 fpfn = PFN_DOWN(faddr);
694 ra_val = GET_SWAP_RA_VAL(vma);
695 pfn = PFN_DOWN(SWAP_RA_ADDR(ra_val));
696 prev_win = SWAP_RA_WIN(ra_val);
697 hits = SWAP_RA_HITS(ra_val);
698 ra_info->win = win = __swapin_nr_pages(pfn, fpfn, hits,
699 max_win, prev_win);
700 atomic_long_set(&vma->swap_readahead_info,
701 SWAP_RA_VAL(faddr, win, 0));
702
703 if (win == 1) {
704 pte_unmap(orig_pte);
705 return;
706 }
707
708
709 if (fpfn == pfn + 1)
710 swap_ra_clamp_pfn(vma, faddr, fpfn, fpfn + win, &start, &end);
711 else if (pfn == fpfn + 1)
712 swap_ra_clamp_pfn(vma, faddr, fpfn - win + 1, fpfn + 1,
713 &start, &end);
714 else {
715 left = (win - 1) / 2;
716 swap_ra_clamp_pfn(vma, faddr, fpfn - left, fpfn + win - left,
717 &start, &end);
718 }
719 ra_info->nr_pte = end - start;
720 ra_info->offset = fpfn - start;
721 pte -= ra_info->offset;
722#ifdef CONFIG_64BIT
723 ra_info->ptes = pte;
724#else
725 tpte = ra_info->ptes;
726 for (pfn = start; pfn != end; pfn++)
727 *tpte++ = *pte++;
728#endif
729 pte_unmap(orig_pte);
730}
731
732static struct page *swap_vma_readahead(swp_entry_t fentry, gfp_t gfp_mask,
733 struct vm_fault *vmf)
734{
735 struct blk_plug plug;
736 struct vm_area_struct *vma = vmf->vma;
737 struct page *page;
738 pte_t *pte, pentry;
739 swp_entry_t entry;
740 unsigned int i;
741 bool page_allocated;
742 struct vma_swap_readahead ra_info = {0,};
743
744 swap_ra_info(vmf, &ra_info);
745 if (ra_info.win == 1)
746 goto skip;
747
748 blk_start_plug(&plug);
749 for (i = 0, pte = ra_info.ptes; i < ra_info.nr_pte;
750 i++, pte++) {
751 pentry = *pte;
752 if (pte_none(pentry))
753 continue;
754 if (pte_present(pentry))
755 continue;
756 entry = pte_to_swp_entry(pentry);
757 if (unlikely(non_swap_entry(entry)))
758 continue;
759 page = __read_swap_cache_async(entry, gfp_mask, vma,
760 vmf->address, &page_allocated);
761 if (!page)
762 continue;
763 if (page_allocated) {
764 swap_readpage(page, false);
765 if (i != ra_info.offset) {
766 SetPageReadahead(page);
767 count_vm_event(SWAP_RA);
768 }
769 }
770 put_page(page);
771 }
772 blk_finish_plug(&plug);
773 lru_add_drain();
774skip:
775 return read_swap_cache_async(fentry, gfp_mask, vma, vmf->address,
776 ra_info.win == 1);
777}
778
779
780
781
782
783
784
785
786
787
788
789
790
791struct page *swapin_readahead(swp_entry_t entry, gfp_t gfp_mask,
792 struct vm_fault *vmf)
793{
794 return swap_use_vma_readahead() ?
795 swap_vma_readahead(entry, gfp_mask, vmf) :
796 swap_cluster_readahead(entry, gfp_mask, vmf);
797}
798
799#ifdef CONFIG_SYSFS
800static ssize_t vma_ra_enabled_show(struct kobject *kobj,
801 struct kobj_attribute *attr, char *buf)
802{
803 return sprintf(buf, "%s\n", enable_vma_readahead ? "true" : "false");
804}
805static ssize_t vma_ra_enabled_store(struct kobject *kobj,
806 struct kobj_attribute *attr,
807 const char *buf, size_t count)
808{
809 if (!strncmp(buf, "true", 4) || !strncmp(buf, "1", 1))
810 enable_vma_readahead = true;
811 else if (!strncmp(buf, "false", 5) || !strncmp(buf, "0", 1))
812 enable_vma_readahead = false;
813 else
814 return -EINVAL;
815
816 return count;
817}
818static struct kobj_attribute vma_ra_enabled_attr =
819 __ATTR(vma_ra_enabled, 0644, vma_ra_enabled_show,
820 vma_ra_enabled_store);
821
822static struct attribute *swap_attrs[] = {
823 &vma_ra_enabled_attr.attr,
824 NULL,
825};
826
827static struct attribute_group swap_attr_group = {
828 .attrs = swap_attrs,
829};
830
831static int __init swap_init_sysfs(void)
832{
833 int err;
834 struct kobject *swap_kobj;
835
836 swap_kobj = kobject_create_and_add("swap", mm_kobj);
837 if (!swap_kobj) {
838 pr_err("failed to create swap kobject\n");
839 return -ENOMEM;
840 }
841 err = sysfs_create_group(swap_kobj, &swap_attr_group);
842 if (err) {
843 pr_err("failed to register swap group\n");
844 goto delete_obj;
845 }
846 return 0;
847
848delete_obj:
849 kobject_put(swap_kobj);
850 return err;
851}
852subsys_initcall(swap_init_sysfs);
853#endif
854