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TOMOYO Linux Cross Reference
Linux/include/linux/swap.h

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  1 /* SPDX-License-Identifier: GPL-2.0 */
  2 #ifndef _LINUX_SWAP_H
  3 #define _LINUX_SWAP_H
  4 
  5 #include <linux/spinlock.h>
  6 #include <linux/linkage.h>
  7 #include <linux/mmzone.h>
  8 #include <linux/list.h>
  9 #include <linux/memcontrol.h>
 10 #include <linux/sched.h>
 11 #include <linux/node.h>
 12 #include <linux/fs.h>
 13 #include <linux/atomic.h>
 14 #include <linux/page-flags.h>
 15 #include <asm/page.h>
 16 
 17 struct notifier_block;
 18 
 19 struct bio;
 20 
 21 struct pagevec;
 22 
 23 #define SWAP_FLAG_PREFER        0x8000  /* set if swap priority specified */
 24 #define SWAP_FLAG_PRIO_MASK     0x7fff
 25 #define SWAP_FLAG_PRIO_SHIFT    0
 26 #define SWAP_FLAG_DISCARD       0x10000 /* enable discard for swap */
 27 #define SWAP_FLAG_DISCARD_ONCE  0x20000 /* discard swap area at swapon-time */
 28 #define SWAP_FLAG_DISCARD_PAGES 0x40000 /* discard page-clusters after use */
 29 
 30 #define SWAP_FLAGS_VALID        (SWAP_FLAG_PRIO_MASK | SWAP_FLAG_PREFER | \
 31                                  SWAP_FLAG_DISCARD | SWAP_FLAG_DISCARD_ONCE | \
 32                                  SWAP_FLAG_DISCARD_PAGES)
 33 #define SWAP_BATCH 64
 34 
 35 static inline int current_is_kswapd(void)
 36 {
 37         return current->flags & PF_KSWAPD;
 38 }
 39 
 40 /*
 41  * MAX_SWAPFILES defines the maximum number of swaptypes: things which can
 42  * be swapped to.  The swap type and the offset into that swap type are
 43  * encoded into pte's and into pgoff_t's in the swapcache.  Using five bits
 44  * for the type means that the maximum number of swapcache pages is 27 bits
 45  * on 32-bit-pgoff_t architectures.  And that assumes that the architecture packs
 46  * the type/offset into the pte as 5/27 as well.
 47  */
 48 #define MAX_SWAPFILES_SHIFT     5
 49 
 50 /*
 51  * Use some of the swap files numbers for other purposes. This
 52  * is a convenient way to hook into the VM to trigger special
 53  * actions on faults.
 54  */
 55 
 56 /*
 57  * Unaddressable device memory support. See include/linux/hmm.h and
 58  * Documentation/vm/hmm.rst. Short description is we need struct pages for
 59  * device memory that is unaddressable (inaccessible) by CPU, so that we can
 60  * migrate part of a process memory to device memory.
 61  *
 62  * When a page is migrated from CPU to device, we set the CPU page table entry
 63  * to a special SWP_DEVICE_* entry.
 64  */
 65 #ifdef CONFIG_DEVICE_PRIVATE
 66 #define SWP_DEVICE_NUM 2
 67 #define SWP_DEVICE_WRITE (MAX_SWAPFILES+SWP_HWPOISON_NUM+SWP_MIGRATION_NUM)
 68 #define SWP_DEVICE_READ (MAX_SWAPFILES+SWP_HWPOISON_NUM+SWP_MIGRATION_NUM+1)
 69 #else
 70 #define SWP_DEVICE_NUM 0
 71 #endif
 72 
 73 /*
 74  * NUMA node memory migration support
 75  */
 76 #ifdef CONFIG_MIGRATION
 77 #define SWP_MIGRATION_NUM 2
 78 #define SWP_MIGRATION_READ      (MAX_SWAPFILES + SWP_HWPOISON_NUM)
 79 #define SWP_MIGRATION_WRITE     (MAX_SWAPFILES + SWP_HWPOISON_NUM + 1)
 80 #else
 81 #define SWP_MIGRATION_NUM 0
 82 #endif
 83 
 84 /*
 85  * Handling of hardware poisoned pages with memory corruption.
 86  */
 87 #ifdef CONFIG_MEMORY_FAILURE
 88 #define SWP_HWPOISON_NUM 1
 89 #define SWP_HWPOISON            MAX_SWAPFILES
 90 #else
 91 #define SWP_HWPOISON_NUM 0
 92 #endif
 93 
 94 #define MAX_SWAPFILES \
 95         ((1 << MAX_SWAPFILES_SHIFT) - SWP_DEVICE_NUM - \
 96         SWP_MIGRATION_NUM - SWP_HWPOISON_NUM)
 97 
 98 /*
 99  * Magic header for a swap area. The first part of the union is
100  * what the swap magic looks like for the old (limited to 128MB)
101  * swap area format, the second part of the union adds - in the
102  * old reserved area - some extra information. Note that the first
103  * kilobyte is reserved for boot loader or disk label stuff...
104  *
105  * Having the magic at the end of the PAGE_SIZE makes detecting swap
106  * areas somewhat tricky on machines that support multiple page sizes.
107  * For 2.5 we'll probably want to move the magic to just beyond the
108  * bootbits...
109  */
110 union swap_header {
111         struct {
112                 char reserved[PAGE_SIZE - 10];
113                 char magic[10];                 /* SWAP-SPACE or SWAPSPACE2 */
114         } magic;
115         struct {
116                 char            bootbits[1024]; /* Space for disklabel etc. */
117                 __u32           version;
118                 __u32           last_page;
119                 __u32           nr_badpages;
120                 unsigned char   sws_uuid[16];
121                 unsigned char   sws_volume[16];
122                 __u32           padding[117];
123                 __u32           badpages[1];
124         } info;
125 };
126 
127 /*
128  * current->reclaim_state points to one of these when a task is running
129  * memory reclaim
130  */
131 struct reclaim_state {
132         unsigned long reclaimed_slab;
133 };
134 
135 #ifdef __KERNEL__
136 
137 struct address_space;
138 struct sysinfo;
139 struct writeback_control;
140 struct zone;
141 
142 /*
143  * A swap extent maps a range of a swapfile's PAGE_SIZE pages onto a range of
144  * disk blocks.  A list of swap extents maps the entire swapfile.  (Where the
145  * term `swapfile' refers to either a blockdevice or an IS_REG file.  Apart
146  * from setup, they're handled identically.
147  *
148  * We always assume that blocks are of size PAGE_SIZE.
149  */
150 struct swap_extent {
151         struct rb_node rb_node;
152         pgoff_t start_page;
153         pgoff_t nr_pages;
154         sector_t start_block;
155 };
156 
157 /*
158  * Max bad pages in the new format..
159  */
160 #define MAX_SWAP_BADPAGES \
161         ((offsetof(union swap_header, magic.magic) - \
162           offsetof(union swap_header, info.badpages)) / sizeof(int))
163 
164 enum {
165         SWP_USED        = (1 << 0),     /* is slot in swap_info[] used? */
166         SWP_WRITEOK     = (1 << 1),     /* ok to write to this swap?    */
167         SWP_DISCARDABLE = (1 << 2),     /* blkdev support discard */
168         SWP_DISCARDING  = (1 << 3),     /* now discarding a free cluster */
169         SWP_SOLIDSTATE  = (1 << 4),     /* blkdev seeks are cheap */
170         SWP_CONTINUED   = (1 << 5),     /* swap_map has count continuation */
171         SWP_BLKDEV      = (1 << 6),     /* its a block device */
172         SWP_ACTIVATED   = (1 << 7),     /* set after swap_activate success */
173         SWP_FS          = (1 << 8),     /* swap file goes through fs */
174         SWP_AREA_DISCARD = (1 << 9),    /* single-time swap area discards */
175         SWP_PAGE_DISCARD = (1 << 10),   /* freed swap page-cluster discards */
176         SWP_STABLE_WRITES = (1 << 11),  /* no overwrite PG_writeback pages */
177         SWP_SYNCHRONOUS_IO = (1 << 12), /* synchronous IO is efficient */
178         SWP_VALID       = (1 << 13),    /* swap is valid to be operated on? */
179                                         /* add others here before... */
180         SWP_SCANNING    = (1 << 14),    /* refcount in scan_swap_map */
181 };
182 
183 #define SWAP_CLUSTER_MAX 32UL
184 #define COMPACT_CLUSTER_MAX SWAP_CLUSTER_MAX
185 
186 #define SWAP_MAP_MAX    0x3e    /* Max duplication count, in first swap_map */
187 #define SWAP_MAP_BAD    0x3f    /* Note pageblock is bad, in first swap_map */
188 #define SWAP_HAS_CACHE  0x40    /* Flag page is cached, in first swap_map */
189 #define SWAP_CONT_MAX   0x7f    /* Max count, in each swap_map continuation */
190 #define COUNT_CONTINUED 0x80    /* See swap_map continuation for full count */
191 #define SWAP_MAP_SHMEM  0xbf    /* Owned by shmem/tmpfs, in first swap_map */
192 
193 /*
194  * We use this to track usage of a cluster. A cluster is a block of swap disk
195  * space with SWAPFILE_CLUSTER pages long and naturally aligns in disk. All
196  * free clusters are organized into a list. We fetch an entry from the list to
197  * get a free cluster.
198  *
199  * The data field stores next cluster if the cluster is free or cluster usage
200  * counter otherwise. The flags field determines if a cluster is free. This is
201  * protected by swap_info_struct.lock.
202  */
203 struct swap_cluster_info {
204         spinlock_t lock;        /*
205                                  * Protect swap_cluster_info fields
206                                  * and swap_info_struct->swap_map
207                                  * elements correspond to the swap
208                                  * cluster
209                                  */
210         unsigned int data:24;
211         unsigned int flags:8;
212 };
213 #define CLUSTER_FLAG_FREE 1 /* This cluster is free */
214 #define CLUSTER_FLAG_NEXT_NULL 2 /* This cluster has no next cluster */
215 #define CLUSTER_FLAG_HUGE 4 /* This cluster is backing a transparent huge page */
216 
217 /*
218  * We assign a cluster to each CPU, so each CPU can allocate swap entry from
219  * its own cluster and swapout sequentially. The purpose is to optimize swapout
220  * throughput.
221  */
222 struct percpu_cluster {
223         struct swap_cluster_info index; /* Current cluster index */
224         unsigned int next; /* Likely next allocation offset */
225 };
226 
227 struct swap_cluster_list {
228         struct swap_cluster_info head;
229         struct swap_cluster_info tail;
230 };
231 
232 /*
233  * The in-memory structure used to track swap areas.
234  */
235 struct swap_info_struct {
236         unsigned long   flags;          /* SWP_USED etc: see above */
237         signed short    prio;           /* swap priority of this type */
238         struct plist_node list;         /* entry in swap_active_head */
239         signed char     type;           /* strange name for an index */
240         unsigned int    max;            /* extent of the swap_map */
241         unsigned char *swap_map;        /* vmalloc'ed array of usage counts */
242         struct swap_cluster_info *cluster_info; /* cluster info. Only for SSD */
243         struct swap_cluster_list free_clusters; /* free clusters list */
244         unsigned int lowest_bit;        /* index of first free in swap_map */
245         unsigned int highest_bit;       /* index of last free in swap_map */
246         unsigned int pages;             /* total of usable pages of swap */
247         unsigned int inuse_pages;       /* number of those currently in use */
248         unsigned int cluster_next;      /* likely index for next allocation */
249         unsigned int cluster_nr;        /* countdown to next cluster search */
250         struct percpu_cluster __percpu *percpu_cluster; /* per cpu's swap location */
251         struct rb_root swap_extent_root;/* root of the swap extent rbtree */
252         struct block_device *bdev;      /* swap device or bdev of swap file */
253         struct file *swap_file;         /* seldom referenced */
254         unsigned int old_block_size;    /* seldom referenced */
255 #ifdef CONFIG_FRONTSWAP
256         unsigned long *frontswap_map;   /* frontswap in-use, one bit per page */
257         atomic_t frontswap_pages;       /* frontswap pages in-use counter */
258 #endif
259         spinlock_t lock;                /*
260                                          * protect map scan related fields like
261                                          * swap_map, lowest_bit, highest_bit,
262                                          * inuse_pages, cluster_next,
263                                          * cluster_nr, lowest_alloc,
264                                          * highest_alloc, free/discard cluster
265                                          * list. other fields are only changed
266                                          * at swapon/swapoff, so are protected
267                                          * by swap_lock. changing flags need
268                                          * hold this lock and swap_lock. If
269                                          * both locks need hold, hold swap_lock
270                                          * first.
271                                          */
272         spinlock_t cont_lock;           /*
273                                          * protect swap count continuation page
274                                          * list.
275                                          */
276         struct work_struct discard_work; /* discard worker */
277         struct swap_cluster_list discard_clusters; /* discard clusters list */
278         struct plist_node avail_lists[0]; /*
279                                            * entries in swap_avail_heads, one
280                                            * entry per node.
281                                            * Must be last as the number of the
282                                            * array is nr_node_ids, which is not
283                                            * a fixed value so have to allocate
284                                            * dynamically.
285                                            * And it has to be an array so that
286                                            * plist_for_each_* can work.
287                                            */
288 };
289 
290 #ifdef CONFIG_64BIT
291 #define SWAP_RA_ORDER_CEILING   5
292 #else
293 /* Avoid stack overflow, because we need to save part of page table */
294 #define SWAP_RA_ORDER_CEILING   3
295 #define SWAP_RA_PTE_CACHE_SIZE  (1 << SWAP_RA_ORDER_CEILING)
296 #endif
297 
298 struct vma_swap_readahead {
299         unsigned short win;
300         unsigned short offset;
301         unsigned short nr_pte;
302 #ifdef CONFIG_64BIT
303         pte_t *ptes;
304 #else
305         pte_t ptes[SWAP_RA_PTE_CACHE_SIZE];
306 #endif
307 };
308 
309 /* linux/mm/workingset.c */
310 void *workingset_eviction(struct page *page);
311 void workingset_refault(struct page *page, void *shadow);
312 void workingset_activation(struct page *page);
313 
314 /* Only track the nodes of mappings with shadow entries */
315 void workingset_update_node(struct xa_node *node);
316 #define mapping_set_update(xas, mapping) do {                           \
317         if (!dax_mapping(mapping) && !shmem_mapping(mapping))           \
318                 xas_set_update(xas, workingset_update_node);            \
319 } while (0)
320 
321 /* linux/mm/page_alloc.c */
322 extern unsigned long totalreserve_pages;
323 extern unsigned long nr_free_buffer_pages(void);
324 extern unsigned long nr_free_pagecache_pages(void);
325 
326 /* Definition of global_zone_page_state not available yet */
327 #define nr_free_pages() global_zone_page_state(NR_FREE_PAGES)
328 
329 
330 /* linux/mm/swap.c */
331 extern void lru_cache_add(struct page *);
332 extern void lru_cache_add_anon(struct page *page);
333 extern void lru_cache_add_file(struct page *page);
334 extern void lru_add_page_tail(struct page *page, struct page *page_tail,
335                          struct lruvec *lruvec, struct list_head *head);
336 extern void activate_page(struct page *);
337 extern void mark_page_accessed(struct page *);
338 extern void lru_add_drain(void);
339 extern void lru_add_drain_cpu(int cpu);
340 extern void lru_add_drain_all(void);
341 extern void rotate_reclaimable_page(struct page *page);
342 extern void deactivate_file_page(struct page *page);
343 extern void mark_page_lazyfree(struct page *page);
344 extern void swap_setup(void);
345 
346 extern void lru_cache_add_active_or_unevictable(struct page *page,
347                                                 struct vm_area_struct *vma);
348 
349 /* linux/mm/vmscan.c */
350 extern unsigned long zone_reclaimable_pages(struct zone *zone);
351 extern unsigned long try_to_free_pages(struct zonelist *zonelist, int order,
352                                         gfp_t gfp_mask, nodemask_t *mask);
353 extern int __isolate_lru_page(struct page *page, isolate_mode_t mode);
354 extern unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *memcg,
355                                                   unsigned long nr_pages,
356                                                   gfp_t gfp_mask,
357                                                   bool may_swap);
358 extern unsigned long mem_cgroup_shrink_node(struct mem_cgroup *mem,
359                                                 gfp_t gfp_mask, bool noswap,
360                                                 pg_data_t *pgdat,
361                                                 unsigned long *nr_scanned);
362 extern unsigned long shrink_all_memory(unsigned long nr_pages);
363 extern int vm_swappiness;
364 extern int remove_mapping(struct address_space *mapping, struct page *page);
365 extern unsigned long vm_total_pages;
366 
367 #ifdef CONFIG_NUMA
368 extern int node_reclaim_mode;
369 extern int sysctl_min_unmapped_ratio;
370 extern int sysctl_min_slab_ratio;
371 #else
372 #define node_reclaim_mode 0
373 #endif
374 
375 extern int page_evictable(struct page *page);
376 extern void check_move_unevictable_pages(struct pagevec *pvec);
377 
378 extern int kswapd_run(int nid);
379 extern void kswapd_stop(int nid);
380 
381 #ifdef CONFIG_SWAP
382 
383 #include <linux/blk_types.h> /* for bio_end_io_t */
384 
385 /* linux/mm/page_io.c */
386 extern int swap_readpage(struct page *page, bool do_poll);
387 extern int swap_writepage(struct page *page, struct writeback_control *wbc);
388 extern void end_swap_bio_write(struct bio *bio);
389 extern int __swap_writepage(struct page *page, struct writeback_control *wbc,
390         bio_end_io_t end_write_func);
391 extern int swap_set_page_dirty(struct page *page);
392 
393 int add_swap_extent(struct swap_info_struct *sis, unsigned long start_page,
394                 unsigned long nr_pages, sector_t start_block);
395 int generic_swapfile_activate(struct swap_info_struct *, struct file *,
396                 sector_t *);
397 
398 /* linux/mm/swap_state.c */
399 /* One swap address space for each 64M swap space */
400 #define SWAP_ADDRESS_SPACE_SHIFT        14
401 #define SWAP_ADDRESS_SPACE_PAGES        (1 << SWAP_ADDRESS_SPACE_SHIFT)
402 extern struct address_space *swapper_spaces[];
403 #define swap_address_space(entry)                           \
404         (&swapper_spaces[swp_type(entry)][swp_offset(entry) \
405                 >> SWAP_ADDRESS_SPACE_SHIFT])
406 extern unsigned long total_swapcache_pages(void);
407 extern void show_swap_cache_info(void);
408 extern int add_to_swap(struct page *page);
409 extern int add_to_swap_cache(struct page *, swp_entry_t, gfp_t);
410 extern int __add_to_swap_cache(struct page *page, swp_entry_t entry);
411 extern void __delete_from_swap_cache(struct page *, swp_entry_t entry);
412 extern void delete_from_swap_cache(struct page *);
413 extern void free_page_and_swap_cache(struct page *);
414 extern void free_pages_and_swap_cache(struct page **, int);
415 extern struct page *lookup_swap_cache(swp_entry_t entry,
416                                       struct vm_area_struct *vma,
417                                       unsigned long addr);
418 extern struct page *read_swap_cache_async(swp_entry_t, gfp_t,
419                         struct vm_area_struct *vma, unsigned long addr,
420                         bool do_poll);
421 extern struct page *__read_swap_cache_async(swp_entry_t, gfp_t,
422                         struct vm_area_struct *vma, unsigned long addr,
423                         bool *new_page_allocated);
424 extern struct page *swap_cluster_readahead(swp_entry_t entry, gfp_t flag,
425                                 struct vm_fault *vmf);
426 extern struct page *swapin_readahead(swp_entry_t entry, gfp_t flag,
427                                 struct vm_fault *vmf);
428 
429 /* linux/mm/swapfile.c */
430 extern atomic_long_t nr_swap_pages;
431 extern long total_swap_pages;
432 extern atomic_t nr_rotate_swap;
433 extern bool has_usable_swap(void);
434 
435 /* Swap 50% full? Release swapcache more aggressively.. */
436 static inline bool vm_swap_full(void)
437 {
438         return atomic_long_read(&nr_swap_pages) * 2 < total_swap_pages;
439 }
440 
441 static inline long get_nr_swap_pages(void)
442 {
443         return atomic_long_read(&nr_swap_pages);
444 }
445 
446 extern void si_swapinfo(struct sysinfo *);
447 extern swp_entry_t get_swap_page(struct page *page);
448 extern void put_swap_page(struct page *page, swp_entry_t entry);
449 extern swp_entry_t get_swap_page_of_type(int);
450 extern int get_swap_pages(int n, swp_entry_t swp_entries[], int entry_size);
451 extern int add_swap_count_continuation(swp_entry_t, gfp_t);
452 extern void swap_shmem_alloc(swp_entry_t);
453 extern int swap_duplicate(swp_entry_t);
454 extern int swapcache_prepare(swp_entry_t);
455 extern void swap_free(swp_entry_t);
456 extern void swapcache_free_entries(swp_entry_t *entries, int n);
457 extern int free_swap_and_cache(swp_entry_t);
458 extern int swap_type_of(dev_t, sector_t, struct block_device **);
459 extern unsigned int count_swap_pages(int, int);
460 extern sector_t map_swap_page(struct page *, struct block_device **);
461 extern sector_t swapdev_block(int, pgoff_t);
462 extern int page_swapcount(struct page *);
463 extern int __swap_count(swp_entry_t entry);
464 extern int __swp_swapcount(swp_entry_t entry);
465 extern int swp_swapcount(swp_entry_t entry);
466 extern struct swap_info_struct *page_swap_info(struct page *);
467 extern struct swap_info_struct *swp_swap_info(swp_entry_t entry);
468 extern bool reuse_swap_page(struct page *, int *);
469 extern int try_to_free_swap(struct page *);
470 struct backing_dev_info;
471 extern int init_swap_address_space(unsigned int type, unsigned long nr_pages);
472 extern void exit_swap_address_space(unsigned int type);
473 extern struct swap_info_struct *get_swap_device(swp_entry_t entry);
474 
475 static inline void put_swap_device(struct swap_info_struct *si)
476 {
477         rcu_read_unlock();
478 }
479 
480 #else /* CONFIG_SWAP */
481 
482 static inline int swap_readpage(struct page *page, bool do_poll)
483 {
484         return 0;
485 }
486 
487 static inline struct swap_info_struct *swp_swap_info(swp_entry_t entry)
488 {
489         return NULL;
490 }
491 
492 #define swap_address_space(entry)               (NULL)
493 #define get_nr_swap_pages()                     0L
494 #define total_swap_pages                        0L
495 #define total_swapcache_pages()                 0UL
496 #define vm_swap_full()                          0
497 
498 #define si_swapinfo(val) \
499         do { (val)->freeswap = (val)->totalswap = 0; } while (0)
500 /* only sparc can not include linux/pagemap.h in this file
501  * so leave put_page and release_pages undeclared... */
502 #define free_page_and_swap_cache(page) \
503         put_page(page)
504 #define free_pages_and_swap_cache(pages, nr) \
505         release_pages((pages), (nr));
506 
507 static inline void show_swap_cache_info(void)
508 {
509 }
510 
511 #define free_swap_and_cache(e) ({(is_migration_entry(e) || is_device_private_entry(e));})
512 #define swapcache_prepare(e) ({(is_migration_entry(e) || is_device_private_entry(e));})
513 
514 static inline int add_swap_count_continuation(swp_entry_t swp, gfp_t gfp_mask)
515 {
516         return 0;
517 }
518 
519 static inline void swap_shmem_alloc(swp_entry_t swp)
520 {
521 }
522 
523 static inline int swap_duplicate(swp_entry_t swp)
524 {
525         return 0;
526 }
527 
528 static inline void swap_free(swp_entry_t swp)
529 {
530 }
531 
532 static inline void put_swap_page(struct page *page, swp_entry_t swp)
533 {
534 }
535 
536 static inline struct page *swap_cluster_readahead(swp_entry_t entry,
537                                 gfp_t gfp_mask, struct vm_fault *vmf)
538 {
539         return NULL;
540 }
541 
542 static inline struct page *swapin_readahead(swp_entry_t swp, gfp_t gfp_mask,
543                         struct vm_fault *vmf)
544 {
545         return NULL;
546 }
547 
548 static inline int swap_writepage(struct page *p, struct writeback_control *wbc)
549 {
550         return 0;
551 }
552 
553 static inline struct page *lookup_swap_cache(swp_entry_t swp,
554                                              struct vm_area_struct *vma,
555                                              unsigned long addr)
556 {
557         return NULL;
558 }
559 
560 static inline int add_to_swap(struct page *page)
561 {
562         return 0;
563 }
564 
565 static inline int add_to_swap_cache(struct page *page, swp_entry_t entry,
566                                                         gfp_t gfp_mask)
567 {
568         return -1;
569 }
570 
571 static inline void __delete_from_swap_cache(struct page *page,
572                                                         swp_entry_t entry)
573 {
574 }
575 
576 static inline void delete_from_swap_cache(struct page *page)
577 {
578 }
579 
580 static inline int page_swapcount(struct page *page)
581 {
582         return 0;
583 }
584 
585 static inline int __swap_count(swp_entry_t entry)
586 {
587         return 0;
588 }
589 
590 static inline int __swp_swapcount(swp_entry_t entry)
591 {
592         return 0;
593 }
594 
595 static inline int swp_swapcount(swp_entry_t entry)
596 {
597         return 0;
598 }
599 
600 #define reuse_swap_page(page, total_map_swapcount) \
601         (page_trans_huge_mapcount(page, total_map_swapcount) == 1)
602 
603 static inline int try_to_free_swap(struct page *page)
604 {
605         return 0;
606 }
607 
608 static inline swp_entry_t get_swap_page(struct page *page)
609 {
610         swp_entry_t entry;
611         entry.val = 0;
612         return entry;
613 }
614 
615 #endif /* CONFIG_SWAP */
616 
617 #ifdef CONFIG_THP_SWAP
618 extern int split_swap_cluster(swp_entry_t entry);
619 #else
620 static inline int split_swap_cluster(swp_entry_t entry)
621 {
622         return 0;
623 }
624 #endif
625 
626 #ifdef CONFIG_MEMCG
627 static inline int mem_cgroup_swappiness(struct mem_cgroup *memcg)
628 {
629         /* Cgroup2 doesn't have per-cgroup swappiness */
630         if (cgroup_subsys_on_dfl(memory_cgrp_subsys))
631                 return vm_swappiness;
632 
633         /* root ? */
634         if (mem_cgroup_disabled() || mem_cgroup_is_root(memcg))
635                 return vm_swappiness;
636 
637         return memcg->swappiness;
638 }
639 #else
640 static inline int mem_cgroup_swappiness(struct mem_cgroup *mem)
641 {
642         return vm_swappiness;
643 }
644 #endif
645 
646 #if defined(CONFIG_SWAP) && defined(CONFIG_MEMCG) && defined(CONFIG_BLK_CGROUP)
647 extern void mem_cgroup_throttle_swaprate(struct mem_cgroup *memcg, int node,
648                                          gfp_t gfp_mask);
649 #else
650 static inline void mem_cgroup_throttle_swaprate(struct mem_cgroup *memcg,
651                                                 int node, gfp_t gfp_mask)
652 {
653 }
654 #endif
655 
656 #ifdef CONFIG_MEMCG_SWAP
657 extern void mem_cgroup_swapout(struct page *page, swp_entry_t entry);
658 extern int mem_cgroup_try_charge_swap(struct page *page, swp_entry_t entry);
659 extern void mem_cgroup_uncharge_swap(swp_entry_t entry, unsigned int nr_pages);
660 extern long mem_cgroup_get_nr_swap_pages(struct mem_cgroup *memcg);
661 extern bool mem_cgroup_swap_full(struct page *page);
662 #else
663 static inline void mem_cgroup_swapout(struct page *page, swp_entry_t entry)
664 {
665 }
666 
667 static inline int mem_cgroup_try_charge_swap(struct page *page,
668                                              swp_entry_t entry)
669 {
670         return 0;
671 }
672 
673 static inline void mem_cgroup_uncharge_swap(swp_entry_t entry,
674                                             unsigned int nr_pages)
675 {
676 }
677 
678 static inline long mem_cgroup_get_nr_swap_pages(struct mem_cgroup *memcg)
679 {
680         return get_nr_swap_pages();
681 }
682 
683 static inline bool mem_cgroup_swap_full(struct page *page)
684 {
685         return vm_swap_full();
686 }
687 #endif
688 
689 #endif /* __KERNEL__*/
690 #endif /* _LINUX_SWAP_H */
691 

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