summaryrefslogtreecommitdiff
path: root/include/linux/swap.h
blob: 1d38d9475c4d0861d7a4597614d0ea225613c568 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
/* SPDX-License-Identifier: GPL-2.0 */
#ifndef _LINUX_SWAP_H
#define _LINUX_SWAP_H

#include <linux/spinlock.h>
#include <linux/linkage.h>
#include <linux/mmzone.h>
#include <linux/list.h>
#include <linux/memcontrol.h>
#include <linux/sched.h>
#include <linux/node.h>
#include <linux/fs.h>
#include <linux/pagemap.h>
#include <linux/atomic.h>
#include <linux/page-flags.h>
#include <uapi/linux/mempolicy.h>
#include <asm/page.h>

struct notifier_block;

struct bio;

struct pagevec;

#define SWAP_FLAG_PREFER	0x8000	/* set if swap priority specified */
#define SWAP_FLAG_PRIO_MASK	0x7fff
#define SWAP_FLAG_PRIO_SHIFT	0
#define SWAP_FLAG_DISCARD	0x10000 /* enable discard for swap */
#define SWAP_FLAG_DISCARD_ONCE	0x20000 /* discard swap area at swapon-time */
#define SWAP_FLAG_DISCARD_PAGES 0x40000 /* discard page-clusters after use */

#define SWAP_FLAGS_VALID	(SWAP_FLAG_PRIO_MASK | SWAP_FLAG_PREFER | \
				 SWAP_FLAG_DISCARD | SWAP_FLAG_DISCARD_ONCE | \
				 SWAP_FLAG_DISCARD_PAGES)
#define SWAP_BATCH 64

static inline int current_is_kswapd(void)
{
	return current->flags & PF_KSWAPD;
}

/*
 * MAX_SWAPFILES defines the maximum number of swaptypes: things which can
 * be swapped to.  The swap type and the offset into that swap type are
 * encoded into pte's and into pgoff_t's in the swapcache.  Using five bits
 * for the type means that the maximum number of swapcache pages is 27 bits
 * on 32-bit-pgoff_t architectures.  And that assumes that the architecture packs
 * the type/offset into the pte as 5/27 as well.
 */
#define MAX_SWAPFILES_SHIFT	5

/*
 * Use some of the swap files numbers for other purposes. This
 * is a convenient way to hook into the VM to trigger special
 * actions on faults.
 */

/*
 * Unaddressable device memory support. See include/linux/hmm.h and
 * Documentation/vm/hmm.rst. Short description is we need struct pages for
 * device memory that is unaddressable (inaccessible) by CPU, so that we can
 * migrate part of a process memory to device memory.
 *
 * When a page is migrated from CPU to device, we set the CPU page table entry
 * to a special SWP_DEVICE_{READ|WRITE} entry.
 *
 * When a page is mapped by the device for exclusive access we set the CPU page
 * table entries to special SWP_DEVICE_EXCLUSIVE_* entries.
 */
#ifdef CONFIG_DEVICE_PRIVATE
#define SWP_DEVICE_NUM 4
#define SWP_DEVICE_WRITE (MAX_SWAPFILES+SWP_HWPOISON_NUM+SWP_MIGRATION_NUM)
#define SWP_DEVICE_READ (MAX_SWAPFILES+SWP_HWPOISON_NUM+SWP_MIGRATION_NUM+1)
#define SWP_DEVICE_EXCLUSIVE_WRITE (MAX_SWAPFILES+SWP_HWPOISON_NUM+SWP_MIGRATION_NUM+2)
#define SWP_DEVICE_EXCLUSIVE_READ (MAX_SWAPFILES+SWP_HWPOISON_NUM+SWP_MIGRATION_NUM+3)
#else
#define SWP_DEVICE_NUM 0
#endif

/*
 * NUMA node memory migration support
 */
#ifdef CONFIG_MIGRATION
#define SWP_MIGRATION_NUM 2
#define SWP_MIGRATION_READ	(MAX_SWAPFILES + SWP_HWPOISON_NUM)
#define SWP_MIGRATION_WRITE	(MAX_SWAPFILES + SWP_HWPOISON_NUM + 1)
#else
#define SWP_MIGRATION_NUM 0
#endif

/*
 * Handling of hardware poisoned pages with memory corruption.
 */
#ifdef CONFIG_MEMORY_FAILURE
#define SWP_HWPOISON_NUM 1
#define SWP_HWPOISON		MAX_SWAPFILES
#else
#define SWP_HWPOISON_NUM 0
#endif

#define MAX_SWAPFILES \
	((1 << MAX_SWAPFILES_SHIFT) - SWP_DEVICE_NUM - \
	SWP_MIGRATION_NUM - SWP_HWPOISON_NUM)

/*
 * Magic header for a swap area. The first part of the union is
 * what the swap magic looks like for the old (limited to 128MB)
 * swap area format, the second part of the union adds - in the
 * old reserved area - some extra information. Note that the first
 * kilobyte is reserved for boot loader or disk label stuff...
 *
 * Having the magic at the end of the PAGE_SIZE makes detecting swap
 * areas somewhat tricky on machines that support multiple page sizes.
 * For 2.5 we'll probably want to move the magic to just beyond the
 * bootbits...
 */
union swap_header {
	struct {
		char reserved[PAGE_SIZE - 10];
		char magic[10];			/* SWAP-SPACE or SWAPSPACE2 */
	} magic;
	struct {
		char		bootbits[1024];	/* Space for disklabel etc. */
		__u32		version;
		__u32		last_page;
		__u32		nr_badpages;
		unsigned char	sws_uuid[16];
		unsigned char	sws_volume[16];
		__u32		padding[117];
		__u32		badpages[1];
	} info;
};

/*
 * current->reclaim_state points to one of these when a task is running
 * memory reclaim
 */
struct reclaim_state {
	unsigned long reclaimed_slab;
};

#ifdef __KERNEL__

struct address_space;
struct sysinfo;
struct writeback_control;
struct zone;

/*
 * A swap extent maps a range of a swapfile's PAGE_SIZE pages onto a range of
 * disk blocks.  A list of swap extents maps the entire swapfile.  (Where the
 * term `swapfile' refers to either a blockdevice or an IS_REG file.  Apart
 * from setup, they're handled identically.
 *
 * We always assume that blocks are of size PAGE_SIZE.
 */
struct swap_extent {
	struct rb_node rb_node;
	pgoff_t start_page;
	pgoff_t nr_pages;
	sector_t start_block;
};

/*
 * Max bad pages in the new format..
 */
#define MAX_SWAP_BADPAGES \
	((offsetof(union swap_header, magic.magic) - \
	  offsetof(union swap_header, info.badpages)) / sizeof(int))

enum {
	SWP_USED	= (1 << 0),	/* is slot in swap_info[] used? */
	SWP_WRITEOK	= (1 << 1),	/* ok to write to this swap?	*/
	SWP_DISCARDABLE = (1 << 2),	/* blkdev support discard */
	SWP_DISCARDING	= (1 << 3),	/* now discarding a free cluster */
	SWP_SOLIDSTATE	= (1 << 4),	/* blkdev seeks are cheap */
	SWP_CONTINUED	= (1 << 5),	/* swap_map has count continuation */
	SWP_BLKDEV	= (1 << 6),	/* its a block device */
	SWP_ACTIVATED	= (1 << 7),	/* set after swap_activate success */
	SWP_FS_OPS	= (1 << 8),	/* swapfile operations go through fs */
	SWP_AREA_DISCARD = (1 << 9),	/* single-time swap area discards */
	SWP_PAGE_DISCARD = (1 << 10),	/* freed swap page-cluster discards */
	SWP_STABLE_WRITES = (1 << 11),	/* no overwrite PG_writeback pages */
	SWP_SYNCHRONOUS_IO = (1 << 12),	/* synchronous IO is efficient */
					/* add others here before... */
	SWP_SCANNING	= (1 << 14),	/* refcount in scan_swap_map */
};

#define SWAP_CLUSTER_MAX 32UL
#define COMPACT_CLUSTER_MAX SWAP_CLUSTER_MAX

/* Bit flag in swap_map */
#define SWAP_HAS_CACHE	0x40	/* Flag page is cached, in first swap_map */
#define COUNT_CONTINUED	0x80	/* Flag swap_map continuation for full count */

/* Special value in first swap_map */
#define SWAP_MAP_MAX	0x3e	/* Max count */
#define SWAP_MAP_BAD	0x3f	/* Note page is bad */
#define SWAP_MAP_SHMEM	0xbf	/* Owned by shmem/tmpfs */

/* Special value in each swap_map continuation */
#define SWAP_CONT_MAX	0x7f	/* Max count */

/*
 * We use this to track usage of a cluster. A cluster is a block of swap disk
 * space with SWAPFILE_CLUSTER pages long and naturally aligns in disk. All
 * free clusters are organized into a list. We fetch an entry from the list to
 * get a free cluster.
 *
 * The data field stores next cluster if the cluster is free or cluster usage
 * counter otherwise. The flags field determines if a cluster is free. This is
 * protected by swap_info_struct.lock.
 */
struct swap_cluster_info {
	spinlock_t lock;	/*
				 * Protect swap_cluster_info fields
				 * and swap_info_struct->swap_map
				 * elements correspond to the swap
				 * cluster
				 */
	unsigned int data:24;
	unsigned int flags:8;
};
#define CLUSTER_FLAG_FREE 1 /* This cluster is free */
#define CLUSTER_FLAG_NEXT_NULL 2 /* This cluster has no next cluster */
#define CLUSTER_FLAG_HUGE 4 /* This cluster is backing a transparent huge page */

/*
 * We assign a cluster to each CPU, so each CPU can allocate swap entry from
 * its own cluster and swapout sequentially. The purpose is to optimize swapout
 * throughput.
 */
struct percpu_cluster {
	struct swap_cluster_info index; /* Current cluster index */
	unsigned int next; /* Likely next allocation offset */
};

struct swap_cluster_list {
	struct swap_cluster_info head;
	struct swap_cluster_info tail;
};

/*
 * The in-memory structure used to track swap areas.
 */
struct swap_info_struct {
	struct percpu_ref users;	/* indicate and keep swap device valid. */
	unsigned long	flags;		/* SWP_USED etc: see above */
	signed short	prio;		/* swap priority of this type */
	struct plist_node list;		/* entry in swap_active_head */
	signed char	type;		/* strange name for an index */
	unsigned int	max;		/* extent of the swap_map */
	unsigned char *swap_map;	/* vmalloc'ed array of usage counts */
	struct swap_cluster_info *cluster_info; /* cluster info. Only for SSD */
	struct swap_cluster_list free_clusters; /* free clusters list */
	unsigned int lowest_bit;	/* index of first free in swap_map */
	unsigned int highest_bit;	/* index of last free in swap_map */
	unsigned int pages;		/* total of usable pages of swap */
	unsigned int inuse_pages;	/* number of those currently in use */
	unsigned int cluster_next;	/* likely index for next allocation */
	unsigned int cluster_nr;	/* countdown to next cluster search */
	unsigned int __percpu *cluster_next_cpu; /*percpu index for next allocation */
	struct percpu_cluster __percpu *percpu_cluster; /* per cpu's swap location */
	struct rb_root swap_extent_root;/* root of the swap extent rbtree */
	struct block_device *bdev;	/* swap device or bdev of swap file */
	struct file *swap_file;		/* seldom referenced */
	unsigned int old_block_size;	/* seldom referenced */
	struct completion comp;		/* seldom referenced */
#ifdef CONFIG_FRONTSWAP
	unsigned long *frontswap_map;	/* frontswap in-use, one bit per page */
	atomic_t frontswap_pages;	/* frontswap pages in-use counter */
#endif
	spinlock_t lock;		/*
					 * protect map scan related fields like
					 * swap_map, lowest_bit, highest_bit,
					 * inuse_pages, cluster_next,
					 * cluster_nr, lowest_alloc,
					 * highest_alloc, free/discard cluster
					 * list. other fields are only changed
					 * at swapon/swapoff, so are protected
					 * by swap_lock. changing flags need
					 * hold this lock and swap_lock. If
					 * both locks need hold, hold swap_lock
					 * first.
					 */
	spinlock_t cont_lock;		/*
					 * protect swap count continuation page
					 * list.
					 */
	struct work_struct discard_work; /* discard worker */
	struct swap_cluster_list discard_clusters; /* discard clusters list */
	struct plist_node avail_lists[]; /*
					   * entries in swap_avail_heads, one
					   * entry per node.
					   * Must be last as the number of the
					   * array is nr_node_ids, which is not
					   * a fixed value so have to allocate
					   * dynamically.
					   * And it has to be an array so that
					   * plist_for_each_* can work.
					   */
};

#ifdef CONFIG_64BIT
#define SWAP_RA_ORDER_CEILING	5
#else
/* Avoid stack overflow, because we need to save part of page table */
#define SWAP_RA_ORDER_CEILING	3
#define SWAP_RA_PTE_CACHE_SIZE	(1 << SWAP_RA_ORDER_CEILING)
#endif

struct vma_swap_readahead {
	unsigned short win;
	unsigned short offset;
	unsigned short nr_pte;
#ifdef CONFIG_64BIT
	pte_t *ptes;
#else
	pte_t ptes[SWAP_RA_PTE_CACHE_SIZE];
#endif
};

static inline swp_entry_t folio_swap_entry(struct folio *folio)
{
	swp_entry_t entry = { .val = page_private(&folio->page) };
	return entry;
}

/* linux/mm/workingset.c */
void workingset_age_nonresident(struct lruvec *lruvec, unsigned long nr_pages);
void *workingset_eviction(struct page *page, struct mem_cgroup *target_memcg);
void workingset_refault(struct folio *folio, void *shadow);
void workingset_activation(struct folio *folio);

/* Only track the nodes of mappings with shadow entries */
void workingset_update_node(struct xa_node *node);
#define mapping_set_update(xas, mapping) do {				\
	if (!dax_mapping(mapping) && !shmem_mapping(mapping))		\
		xas_set_update(xas, workingset_update_node);		\
} while (0)

/* linux/mm/page_alloc.c */
extern unsigned long totalreserve_pages;

/* Definition of global_zone_page_state not available yet */
#define nr_free_pages() global_zone_page_state(NR_FREE_PAGES)


/* linux/mm/swap.c */
extern void lru_note_cost(struct lruvec *lruvec, bool file,
			  unsigned int nr_pages);
extern void lru_note_cost_folio(struct folio *);
extern void folio_add_lru(struct folio *);
extern void lru_cache_add(struct page *);
void mark_page_accessed(struct page *);
void folio_mark_accessed(struct folio *);

extern atomic_t lru_disable_count;

static inline bool lru_cache_disabled(void)
{
	return atomic_read(&lru_disable_count);
}

static inline void lru_cache_enable(void)
{
	atomic_dec(&lru_disable_count);
}

extern void lru_cache_disable(void);
extern void lru_add_drain(void);
extern void lru_add_drain_cpu(int cpu);
extern void lru_add_drain_cpu_zone(struct zone *zone);
extern void lru_add_drain_all(void);
extern void deactivate_file_page(struct page *page);
extern void deactivate_page(struct page *page);
extern void mark_page_lazyfree(struct page *page);
extern void swap_setup(void);

extern void lru_cache_add_inactive_or_unevictable(struct page *page,
						struct vm_area_struct *vma);

/* linux/mm/vmscan.c */
extern unsigned long zone_reclaimable_pages(struct zone *zone);
extern unsigned long try_to_free_pages(struct zonelist *zonelist, int order,
					gfp_t gfp_mask, nodemask_t *mask);
extern bool __isolate_lru_page_prepare(struct page *page, isolate_mode_t mode);
extern unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *memcg,
						  unsigned long nr_pages,
						  gfp_t gfp_mask,
						  bool may_swap);
extern unsigned long mem_cgroup_shrink_node(struct mem_cgroup *mem,
						gfp_t gfp_mask, bool noswap,
						pg_data_t *pgdat,
						unsigned long *nr_scanned);
extern unsigned long shrink_all_memory(unsigned long nr_pages);
extern int vm_swappiness;
extern int remove_mapping(struct address_space *mapping, struct page *page);

extern unsigned long reclaim_pages(struct list_head *page_list);
#ifdef CONFIG_NUMA
extern int node_reclaim_mode;
extern int sysctl_min_unmapped_ratio;
extern int sysctl_min_slab_ratio;
#else
#define node_reclaim_mode 0
#endif

static inline bool node_reclaim_enabled(void)
{
	/* Is any node_reclaim_mode bit set? */
	return node_reclaim_mode & (RECLAIM_ZONE|RECLAIM_WRITE|RECLAIM_UNMAP);
}

extern void check_move_unevictable_pages(struct pagevec *pvec);

extern void kswapd_run(int nid);
extern void kswapd_stop(int nid);

#ifdef CONFIG_SWAP

#include <linux/blk_types.h> /* for bio_end_io_t */

/* linux/mm/page_io.c */
extern int swap_readpage(struct page *page, bool do_poll);
extern int swap_writepage(struct page *page, struct writeback_control *wbc);
extern void end_swap_bio_write(struct bio *bio);
extern int __swap_writepage(struct page *page, struct writeback_control *wbc,
	bio_end_io_t end_write_func);
extern int swap_set_page_dirty(struct page *page);

int add_swap_extent(struct swap_info_struct *sis, unsigned long start_page,
		unsigned long nr_pages, sector_t start_block);
int generic_swapfile_activate(struct swap_info_struct *, struct file *,
		sector_t *);

/* linux/mm/swap_state.c */
/* One swap address space for each 64M swap space */
#define SWAP_ADDRESS_SPACE_SHIFT	14
#define SWAP_ADDRESS_SPACE_PAGES	(1 << SWAP_ADDRESS_SPACE_SHIFT)
extern struct address_space *swapper_spaces[];
#define swap_address_space(entry)			    \
	(&swapper_spaces[swp_type(entry)][swp_offset(entry) \
		>> SWAP_ADDRESS_SPACE_SHIFT])
static inline unsigned long total_swapcache_pages(void)
{
	return global_node_page_state(NR_SWAPCACHE);
}

extern void show_swap_cache_info(void);
extern int add_to_swap(struct page *page);
extern void *get_shadow_from_swap_cache(swp_entry_t entry);
extern int add_to_swap_cache(struct page *page, swp_entry_t entry,
			gfp_t gfp, void **shadowp);
extern void __delete_from_swap_cache(struct page *page,
			swp_entry_t entry, void *shadow);
extern void delete_from_swap_cache(struct page *);
extern void clear_shadow_from_swap_cache(int type, unsigned long begin,
				unsigned long end);
extern void free_swap_cache(struct page *);
extern void free_page_and_swap_cache(struct page *);
extern void free_pages_and_swap_cache(struct page **, int);
extern struct page *lookup_swap_cache(swp_entry_t entry,
				      struct vm_area_struct *vma,
				      unsigned long addr);
struct page *find_get_incore_page(struct address_space *mapping, pgoff_t index);
extern struct page *read_swap_cache_async(swp_entry_t, gfp_t,
			struct vm_area_struct *vma, unsigned long addr,
			bool do_poll);
extern struct page *__read_swap_cache_async(swp_entry_t, gfp_t,
			struct vm_area_struct *vma, unsigned long addr,
			bool *new_page_allocated);
extern struct page *swap_cluster_readahead(swp_entry_t entry, gfp_t flag,
				struct vm_fault *vmf);
extern struct page *swapin_readahead(swp_entry_t entry, gfp_t flag,
				struct vm_fault *vmf);

/* linux/mm/swapfile.c */
extern atomic_long_t nr_swap_pages;
extern long total_swap_pages;
extern atomic_t nr_rotate_swap;
extern bool has_usable_swap(void);

/* Swap 50% full? Release swapcache more aggressively.. */
static inline bool vm_swap_full(void)
{
	return atomic_long_read(&nr_swap_pages) * 2 < total_swap_pages;
}

static inline long get_nr_swap_pages(void)
{
	return atomic_long_read(&nr_swap_pages);
}

extern void si_swapinfo(struct sysinfo *);
extern swp_entry_t get_swap_page(struct page *page);
extern void put_swap_page(struct page *page, swp_entry_t entry);
extern swp_entry_t get_swap_page_of_type(int);
extern int get_swap_pages(int n, swp_entry_t swp_entries[], int entry_size);
extern int add_swap_count_continuation(swp_entry_t, gfp_t);
extern void swap_shmem_alloc(swp_entry_t);
extern int swap_duplicate(swp_entry_t);
extern int swapcache_prepare(swp_entry_t);
extern void swap_free(swp_entry_t);
extern void swapcache_free_entries(swp_entry_t *entries, int n);
extern int free_swap_and_cache(swp_entry_t);
int swap_type_of(dev_t device, sector_t offset);
int find_first_swap(dev_t *device);
extern unsigned int count_swap_pages(int, int);
extern sector_t swapdev_block(int, pgoff_t);
extern int page_swapcount(struct page *);
extern int __swap_count(swp_entry_t entry);
extern int __swp_swapcount(swp_entry_t entry);
extern int swp_swapcount(swp_entry_t entry);
extern struct swap_info_struct *page_swap_info(struct page *);
extern struct swap_info_struct *swp_swap_info(swp_entry_t entry);
extern bool reuse_swap_page(struct page *);
extern int try_to_free_swap(struct page *);
struct backing_dev_info;
extern int init_swap_address_space(unsigned int type, unsigned long nr_pages);
extern void exit_swap_address_space(unsigned int type);
extern struct swap_info_struct *get_swap_device(swp_entry_t entry);
sector_t swap_page_sector(struct page *page);

static inline void put_swap_device(struct swap_info_struct *si)
{
	percpu_ref_put(&si->users);
}

#else /* CONFIG_SWAP */

static inline int swap_readpage(struct page *page, bool do_poll)
{
	return 0;
}

static inline struct swap_info_struct *swp_swap_info(swp_entry_t entry)
{
	return NULL;
}

static inline struct swap_info_struct *get_swap_device(swp_entry_t entry)
{
	return NULL;
}

static inline void put_swap_device(struct swap_info_struct *si)
{
}

static inline struct address_space *swap_address_space(swp_entry_t entry)
{
	return NULL;
}

#define get_nr_swap_pages()			0L
#define total_swap_pages			0L
#define total_swapcache_pages()			0UL
#define vm_swap_full()				0

#define si_swapinfo(val) \
	do { (val)->freeswap = (val)->totalswap = 0; } while (0)
/* only sparc can not include linux/pagemap.h in this file
 * so leave put_page and release_pages undeclared... */
#define free_page_and_swap_cache(page) \
	put_page(page)
#define free_pages_and_swap_cache(pages, nr) \
	release_pages((pages), (nr));

static inline void free_swap_cache(struct page *page)
{
}

static inline void show_swap_cache_info(void)
{
}

/* used to sanity check ptes in zap_pte_range when CONFIG_SWAP=0 */
#define free_swap_and_cache(e) is_pfn_swap_entry(e)

static inline int add_swap_count_continuation(swp_entry_t swp, gfp_t gfp_mask)
{
	return 0;
}

static inline void swap_shmem_alloc(swp_entry_t swp)
{
}

static inline int swap_duplicate(swp_entry_t swp)
{
	return 0;
}

static inline void swap_free(swp_entry_t swp)
{
}

static inline void put_swap_page(struct page *page, swp_entry_t swp)
{
}

static inline struct page *swap_cluster_readahead(swp_entry_t entry,
				gfp_t gfp_mask, struct vm_fault *vmf)
{
	return NULL;
}

static inline struct page *swapin_readahead(swp_entry_t swp, gfp_t gfp_mask,
			struct vm_fault *vmf)
{
	return NULL;
}

static inline int swap_writepage(struct page *p, struct writeback_control *wbc)
{
	return 0;
}

static inline struct page *lookup_swap_cache(swp_entry_t swp,
					     struct vm_area_struct *vma,
					     unsigned long addr)
{
	return NULL;
}

static inline
struct page *find_get_incore_page(struct address_space *mapping, pgoff_t index)
{
	return find_get_page(mapping, index);
}

static inline int add_to_swap(struct page *page)
{
	return 0;
}

static inline void *get_shadow_from_swap_cache(swp_entry_t entry)
{
	return NULL;
}

static inline int add_to_swap_cache(struct page *page, swp_entry_t entry,
					gfp_t gfp_mask, void **shadowp)
{
	return -1;
}

static inline void __delete_from_swap_cache(struct page *page,
					swp_entry_t entry, void *shadow)
{
}

static inline void delete_from_swap_cache(struct page *page)
{
}

static inline void clear_shadow_from_swap_cache(int type, unsigned long begin,
				unsigned long end)
{
}

static inline int page_swapcount(struct page *page)
{
	return 0;
}

static inline int __swap_count(swp_entry_t entry)
{
	return 0;
}

static inline int __swp_swapcount(swp_entry_t entry)
{
	return 0;
}

static inline int swp_swapcount(swp_entry_t entry)
{
	return 0;
}

#define reuse_swap_page(page) \
	(page_trans_huge_mapcount(page) == 1)

static inline int try_to_free_swap(struct page *page)
{
	return 0;
}

static inline swp_entry_t get_swap_page(struct page *page)
{
	swp_entry_t entry;
	entry.val = 0;
	return entry;
}

#endif /* CONFIG_SWAP */

#ifdef CONFIG_THP_SWAP
extern int split_swap_cluster(swp_entry_t entry);
#else
static inline int split_swap_cluster(swp_entry_t entry)
{
	return 0;
}
#endif

#ifdef CONFIG_MEMCG
static inline int mem_cgroup_swappiness(struct mem_cgroup *memcg)
{
	/* Cgroup2 doesn't have per-cgroup swappiness */
	if (cgroup_subsys_on_dfl(memory_cgrp_subsys))
		return vm_swappiness;

	/* root ? */
	if (mem_cgroup_disabled() || mem_cgroup_is_root(memcg))
		return vm_swappiness;

	return memcg->swappiness;
}
#else
static inline int mem_cgroup_swappiness(struct mem_cgroup *mem)
{
	return vm_swappiness;
}
#endif

#if defined(CONFIG_SWAP) && defined(CONFIG_MEMCG) && defined(CONFIG_BLK_CGROUP)
extern void __cgroup_throttle_swaprate(struct page *page, gfp_t gfp_mask);
static inline  void cgroup_throttle_swaprate(struct page *page, gfp_t gfp_mask)
{
	if (mem_cgroup_disabled())
		return;
	__cgroup_throttle_swaprate(page, gfp_mask);
}
#else
static inline void cgroup_throttle_swaprate(struct page *page, gfp_t gfp_mask)
{
}
#endif

#ifdef CONFIG_MEMCG_SWAP
extern void mem_cgroup_swapout(struct page *page, swp_entry_t entry);
extern int __mem_cgroup_try_charge_swap(struct page *page, swp_entry_t entry);
static inline int mem_cgroup_try_charge_swap(struct page *page, swp_entry_t entry)
{
	if (mem_cgroup_disabled())
		return 0;
	return __mem_cgroup_try_charge_swap(page, entry);
}

extern void __mem_cgroup_uncharge_swap(swp_entry_t entry, unsigned int nr_pages);
static inline void mem_cgroup_uncharge_swap(swp_entry_t entry, unsigned int nr_pages)
{
	if (mem_cgroup_disabled())
		return;
	__mem_cgroup_uncharge_swap(entry, nr_pages);
}

extern long mem_cgroup_get_nr_swap_pages(struct mem_cgroup *memcg);
extern bool mem_cgroup_swap_full(struct page *page);
#else
static inline void mem_cgroup_swapout(struct page *page, swp_entry_t entry)
{
}

static inline int mem_cgroup_try_charge_swap(struct page *page,
					     swp_entry_t entry)
{
	return 0;
}

static inline void mem_cgroup_uncharge_swap(swp_entry_t entry,
					    unsigned int nr_pages)
{
}

static inline long mem_cgroup_get_nr_swap_pages(struct mem_cgroup *memcg)
{
	return get_nr_swap_pages();
}

static inline bool mem_cgroup_swap_full(struct page *page)
{
	return vm_swap_full();
}
#endif

#endif /* __KERNEL__*/
#endif /* _LINUX_SWAP_H */