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

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