include/linux/swap.h

   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.txt. 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_FILE        = (1 << 7),     /* set after swap_activate success */
 171         SWP_AREA_DISCARD = (1 << 8),    /* single-time swap area discards */
 172         SWP_PAGE_DISCARD = (1 << 9),    /* freed swap page-cluster discards */
 173         SWP_STABLE_WRITES = (1 << 10),  /* no overwrite PG_writeback pages */
 174         SWP_SYNCHRONOUS_IO = (1 << 11), /* synchronous IO is efficient */
 175                                         /* add others here before... */
 176         SWP_SCANNING    = (1 << 12),    /* refcount in scan_swap_map */
 177 };
 178
 179 #define SWAP_CLUSTER_MAX 32UL
 180 #define COMPACT_CLUSTER_MAX SWAP_CLUSTER_MAX
 181
 182 #define SWAP_MAP_MAX    0x3e    /* Max duplication count, in first swap_map */
 183 #define SWAP_MAP_BAD    0x3f    /* Note pageblock is bad, in first swap_map */
 184 #define SWAP_HAS_CACHE  0x40    /* Flag page is cached, in first swap_map */
 185 #define SWAP_CONT_MAX   0x7f    /* Max count, in each swap_map continuation */
 186 #define COUNT_CONTINUED 0x80    /* See swap_map continuation for full count */
 187 #define SWAP_MAP_SHMEM  0xbf    /* Owned by shmem/tmpfs, in first swap_map */
 188
 189 /*
 190  * We use this to track usage of a cluster. A cluster is a block of swap disk
 191  * space with SWAPFILE_CLUSTER pages long and naturally aligns in disk. All
 192  * free clusters are organized into a list. We fetch an entry from the list to
 193  * get a free cluster.
 194  *
 195  * The data field stores next cluster if the cluster is free or cluster usage
 196  * counter otherwise. The flags field determines if a cluster is free. This is
 197  * protected by swap_info_struct.lock.
 198  */
 199 struct swap_cluster_info {
 200         spinlock_t lock;        /*
 201                                  * Protect swap_cluster_info fields
 202                                  * and swap_info_struct->swap_map
 203                                  * elements correspond to the swap
 204                                  * cluster
 205                                  */
 206         unsigned int data:24;
 207         unsigned int flags:8;
 208 };
 209 #define CLUSTER_FLAG_FREE 1 /* This cluster is free */
 210 #define CLUSTER_FLAG_NEXT_NULL 2 /* This cluster has no next cluster */
 211 #define CLUSTER_FLAG_HUGE 4 /* This cluster is backing a transparent huge page */
 212
 213 /*
 214  * We assign a cluster to each CPU, so each CPU can allocate swap entry from
 215  * its own cluster and swapout sequentially. The purpose is to optimize swapout
 216  * throughput.
 217  */
 218 struct percpu_cluster {
 219         struct swap_cluster_info index; /* Current cluster index */
 220         unsigned int next; /* Likely next allocation offset */
 221 };
 222
 223 struct swap_cluster_list {
 224         struct swap_cluster_info head;
 225         struct swap_cluster_info tail;
 226 };
 227
 228 /*
 229  * The in-memory structure used to track swap areas.
 230  */
 231 struct swap_info_struct {
 232         unsigned long   flags;          /* SWP_USED etc: see above */
 233         signed short    prio;           /* swap priority of this type */
 234         struct plist_node list;         /* entry in swap_active_head */
 235         struct plist_node avail_lists[MAX_NUMNODES];/* entry in swap_avail_heads */
 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 };
 277
 278 #ifdef CONFIG_64BIT
 279 #define SWAP_RA_ORDER_CEILING   5
 280 #else
 281 /* Avoid stack overflow, because we need to save part of page table */
 282 #define SWAP_RA_ORDER_CEILING   3
 283 #define SWAP_RA_PTE_CACHE_SIZE  (1 << SWAP_RA_ORDER_CEILING)
 284 #endif
 285
 286 struct vma_swap_readahead {
 287         unsigned short win;
 288         unsigned short offset;
 289         unsigned short nr_pte;
 290 #ifdef CONFIG_64BIT
 291         pte_t *ptes;
 292 #else
 293         pte_t ptes[SWAP_RA_PTE_CACHE_SIZE];
 294 #endif
 295 };
 296
 297 /* linux/mm/workingset.c */
 298 void *workingset_eviction(struct address_space *mapping, struct page *page);
 299 bool workingset_refault(void *shadow);
 300 void workingset_activation(struct page *page);
 301
 302 /* Do not use directly, use workingset_lookup_update */
 303 void workingset_update_node(struct radix_tree_node *node);
 304
 305 /* Returns workingset_update_node() if the mapping has shadow entries. */
 306 #define workingset_lookup_update(mapping)                               \
 307 ({                                                                      \
 308         radix_tree_update_node_t __helper = workingset_update_node;     \
 309         if (dax_mapping(mapping) || shmem_mapping(mapping))             \
 310                 __helper = NULL;                                        \
 311         __helper;                                                       \
 312 })
 313
 314 /* linux/mm/page_alloc.c */
 315 extern unsigned long totalram_pages;
 316 extern unsigned long totalreserve_pages;
 317 extern unsigned long nr_free_buffer_pages(void);
 318 extern unsigned long nr_free_pagecache_pages(void);
 319
 320 /* Definition of global_zone_page_state not available yet */
 321 #define nr_free_pages() global_zone_page_state(NR_FREE_PAGES)
 322
 323
 324 /* linux/mm/swap.c */
 325 extern void lru_cache_add(struct page *);
 326 extern void lru_cache_add_anon(struct page *page);
 327 extern void lru_cache_add_file(struct page *page);
 328 extern void lru_add_page_tail(struct page *page, struct page *page_tail,
 329                          struct lruvec *lruvec, struct list_head *head);
 330 extern void activate_page(struct page *);
 331 extern void mark_page_accessed(struct page *);
 332 extern void lru_add_drain(void);
 333 extern void lru_add_drain_cpu(int cpu);
 334 extern void lru_add_drain_all(void);
 335 extern void lru_add_drain_all_cpuslocked(void);
 336 extern void rotate_reclaimable_page(struct page *page);
 337 extern void deactivate_file_page(struct page *page);
 338 extern void mark_page_lazyfree(struct page *page);
 339 extern void swap_setup(void);
 340
 341 extern void add_page_to_unevictable_list(struct page *page);
 342
 343 extern void lru_cache_add_active_or_unevictable(struct page *page,
 344                                                 struct vm_area_struct *vma);
 345
 346 /* linux/mm/vmscan.c */
 347 extern unsigned long zone_reclaimable_pages(struct zone *zone);
 348 extern unsigned long pgdat_reclaimable_pages(struct pglist_data *pgdat);
 349 extern unsigned long try_to_free_pages(struct zonelist *zonelist, int order,
 350                                         gfp_t gfp_mask, nodemask_t *mask);
 351 extern int __isolate_lru_page(struct page *page, isolate_mode_t mode);
 352 extern unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *memcg,
 353                                                   unsigned long nr_pages,
 354                                                   gfp_t gfp_mask,
 355                                                   bool may_swap);
 356 extern unsigned long mem_cgroup_shrink_node(struct mem_cgroup *mem,
 357                                                 gfp_t gfp_mask, bool noswap,
 358                                                 pg_data_t *pgdat,
 359                                                 unsigned long *nr_scanned);
 360 extern unsigned long shrink_all_memory(unsigned long nr_pages);
 361 extern int vm_swappiness;
 362 extern int remove_mapping(struct address_space *mapping, struct page *page);
 363 extern unsigned long vm_total_pages;
 364
 365 #ifdef CONFIG_NUMA
 366 extern int node_reclaim_mode;
 367 extern int sysctl_min_unmapped_ratio;
 368 extern int sysctl_min_slab_ratio;
 369 extern int node_reclaim(struct pglist_data *, gfp_t, unsigned int);
 370 #else
 371 #define node_reclaim_mode 0
 372 static inline int node_reclaim(struct pglist_data *pgdat, gfp_t mask,
 373                                 unsigned int order)
 374 {
 375         return 0;
 376 }
 377 #endif
 378
 379 extern int page_evictable(struct page *page);
 380 extern void check_move_unevictable_pages(struct page **, int nr_pages);
 381
 382 extern int kswapd_run(int nid);
 383 extern void kswapd_stop(int nid);
 384
 385 #ifdef CONFIG_SWAP
 386
 387 #include <linux/blk_types.h> /* for bio_end_io_t */
 388
 389 /* linux/mm/page_io.c */
 390 extern int swap_readpage(struct page *page, bool do_poll);
 391 extern int swap_writepage(struct page *page, struct writeback_control *wbc);
 392 extern void end_swap_bio_write(struct bio *bio);
 393 extern int __swap_writepage(struct page *page, struct writeback_control *wbc,
 394         bio_end_io_t end_write_func);
 395 extern int swap_set_page_dirty(struct page *page);
 396
 397 int add_swap_extent(struct swap_info_struct *sis, unsigned long start_page,
 398                 unsigned long nr_pages, sector_t start_block);
 399 int generic_swapfile_activate(struct swap_info_struct *, struct file *,
 400                 sector_t *);
 401
 402 /* linux/mm/swap_state.c */
 403 /* One swap address space for each 64M swap space */
 404 #define SWAP_ADDRESS_SPACE_SHIFT        14
 405 #define SWAP_ADDRESS_SPACE_PAGES        (1 << SWAP_ADDRESS_SPACE_SHIFT)
 406 extern struct address_space *swapper_spaces[];
 407 extern bool swap_vma_readahead;
 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 *);
 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 *swapin_readahead(swp_entry_t, gfp_t,
 430                         struct vm_area_struct *vma, unsigned long addr);
 431
 432 extern struct page *swap_readahead_detect(struct vm_fault *vmf,
 433                                           struct vma_swap_readahead *swap_ra);
 434 extern struct page *do_swap_page_readahead(swp_entry_t fentry, gfp_t gfp_mask,
 435                                            struct vm_fault *vmf,
 436                                            struct vma_swap_readahead *swap_ra);
 437
 438 /* linux/mm/swapfile.c */
 439 extern atomic_long_t nr_swap_pages;
 440 extern long total_swap_pages;
 441 extern atomic_t nr_rotate_swap;
 442 extern bool has_usable_swap(void);
 443
 444 static inline bool swap_use_vma_readahead(void)
 445 {
 446         return READ_ONCE(swap_vma_readahead) && !atomic_read(&nr_rotate_swap);
 447 }
 448
 449 /* Swap 50% full? Release swapcache more aggressively.. */
 450 static inline bool vm_swap_full(void)
 451 {
 452         return atomic_long_read(&nr_swap_pages) * 2 < total_swap_pages;
 453 }
 454
 455 static inline long get_nr_swap_pages(void)
 456 {
 457         return atomic_long_read(&nr_swap_pages);
 458 }
 459
 460 extern void si_swapinfo(struct sysinfo *);
 461 extern swp_entry_t get_swap_page(struct page *page);
 462 extern void put_swap_page(struct page *page, swp_entry_t entry);
 463 extern swp_entry_t get_swap_page_of_type(int);
 464 extern int get_swap_pages(int n, bool cluster, swp_entry_t swp_entries[]);
 465 extern int add_swap_count_continuation(swp_entry_t, gfp_t);
 466 extern void swap_shmem_alloc(swp_entry_t);
 467 extern int swap_duplicate(swp_entry_t);
 468 extern int swapcache_prepare(swp_entry_t);
 469 extern void swap_free(swp_entry_t);
 470 extern void swapcache_free_entries(swp_entry_t *entries, int n);
 471 extern int free_swap_and_cache(swp_entry_t);
 472 extern int swap_type_of(dev_t, sector_t, struct block_device **);
 473 extern unsigned int count_swap_pages(int, int);
 474 extern sector_t map_swap_page(struct page *, struct block_device **);
 475 extern sector_t swapdev_block(int, pgoff_t);
 476 extern int page_swapcount(struct page *);
 477 extern int __swap_count(struct swap_info_struct *si, swp_entry_t entry);
 478 extern int __swp_swapcount(swp_entry_t entry);
 479 extern int swp_swapcount(swp_entry_t entry);
 480 extern struct swap_info_struct *page_swap_info(struct page *);
 481 extern struct swap_info_struct *swp_swap_info(swp_entry_t entry);
 482 extern bool reuse_swap_page(struct page *, int *);
 483 extern int try_to_free_swap(struct page *);
 484 struct backing_dev_info;
 485 extern int init_swap_address_space(unsigned int type, unsigned long nr_pages);
 486 extern void exit_swap_address_space(unsigned int type);
 487
 488 #else /* CONFIG_SWAP */
 489
 490 static inline int swap_readpage(struct page *page, bool do_poll)
 491 {
 492         return 0;
 493 }
 494
 495 static inline struct swap_info_struct *swp_swap_info(swp_entry_t entry)
 496 {
 497         return NULL;
 498 }
 499
 500 #define swap_address_space(entry)               (NULL)
 501 #define get_nr_swap_pages()                     0L
 502 #define total_swap_pages                        0L
 503 #define total_swapcache_pages()                 0UL
 504 #define vm_swap_full()                          0
 505
 506 #define si_swapinfo(val) \
 507         do { (val)->freeswap = (val)->totalswap = 0; } while (0)
 508 /* only sparc can not include linux/pagemap.h in this file
 509  * so leave put_page and release_pages undeclared... */
 510 #define free_page_and_swap_cache(page) \
 511         put_page(page)
 512 #define free_pages_and_swap_cache(pages, nr) \
 513         release_pages((pages), (nr));
 514
 515 static inline void show_swap_cache_info(void)
 516 {
 517 }
 518
 519 #define free_swap_and_cache(e) ({(is_migration_entry(e) || is_device_private_entry(e));})
 520 #define swapcache_prepare(e) ({(is_migration_entry(e) || is_device_private_entry(e));})
 521
 522 static inline int add_swap_count_continuation(swp_entry_t swp, gfp_t gfp_mask)
 523 {
 524         return 0;
 525 }
 526
 527 static inline void swap_shmem_alloc(swp_entry_t swp)
 528 {
 529 }
 530
 531 static inline int swap_duplicate(swp_entry_t swp)
 532 {
 533         return 0;
 534 }
 535
 536 static inline void swap_free(swp_entry_t swp)
 537 {
 538 }
 539
 540 static inline void put_swap_page(struct page *page, swp_entry_t swp)
 541 {
 542 }
 543
 544 static inline struct page *swapin_readahead(swp_entry_t swp, gfp_t gfp_mask,
 545                         struct vm_area_struct *vma, unsigned long addr)
 546 {
 547         return NULL;
 548 }
 549
 550 static inline bool swap_use_vma_readahead(void)
 551 {
 552         return false;
 553 }
 554
 555 static inline struct page *swap_readahead_detect(
 556         struct vm_fault *vmf, struct vma_swap_readahead *swap_ra)
 557 {
 558         return NULL;
 559 }
 560
 561 static inline struct page *do_swap_page_readahead(
 562         swp_entry_t fentry, gfp_t gfp_mask,
 563         struct vm_fault *vmf, struct vma_swap_readahead *swap_ra)
 564 {
 565         return NULL;
 566 }
 567
 568 static inline int swap_writepage(struct page *p, struct writeback_control *wbc)
 569 {
 570         return 0;
 571 }
 572
 573 static inline struct page *lookup_swap_cache(swp_entry_t swp,
 574                                              struct vm_area_struct *vma,
 575                                              unsigned long addr)
 576 {
 577         return NULL;
 578 }
 579
 580 static inline int add_to_swap(struct page *page)
 581 {
 582         return 0;
 583 }
 584
 585 static inline int add_to_swap_cache(struct page *page, swp_entry_t entry,
 586                                                         gfp_t gfp_mask)
 587 {
 588         return -1;
 589 }
 590
 591 static inline void __delete_from_swap_cache(struct page *page)
 592 {
 593 }
 594
 595 static inline void delete_from_swap_cache(struct page *page)
 596 {
 597 }
 598
 599 static inline int page_swapcount(struct page *page)
 600 {
 601         return 0;
 602 }
 603
 604 static inline int __swap_count(struct swap_info_struct *si, swp_entry_t entry)
 605 {
 606         return 0;
 607 }
 608
 609 static inline int __swp_swapcount(swp_entry_t entry)
 610 {
 611         return 0;
 612 }
 613
 614 static inline int swp_swapcount(swp_entry_t entry)
 615 {
 616         return 0;
 617 }
 618
 619 #define reuse_swap_page(page, total_map_swapcount) \
 620         (page_trans_huge_mapcount(page, total_map_swapcount) == 1)
 621
 622 static inline int try_to_free_swap(struct page *page)
 623 {
 624         return 0;
 625 }
 626
 627 static inline swp_entry_t get_swap_page(struct page *page)
 628 {
 629         swp_entry_t entry;
 630         entry.val = 0;
 631         return entry;
 632 }
 633
 634 #endif /* CONFIG_SWAP */
 635
 636 #ifdef CONFIG_THP_SWAP
 637 extern int split_swap_cluster(swp_entry_t entry);
 638 #else
 639 static inline int split_swap_cluster(swp_entry_t entry)
 640 {
 641         return 0;
 642 }
 643 #endif
 644
 645 #ifdef CONFIG_MEMCG
 646 static inline int mem_cgroup_swappiness(struct mem_cgroup *memcg)
 647 {
 648         /* Cgroup2 doesn't have per-cgroup swappiness */
 649         if (cgroup_subsys_on_dfl(memory_cgrp_subsys))
 650                 return vm_swappiness;
 651
 652         /* root ? */
 653         if (mem_cgroup_disabled() || !memcg->css.parent)
 654                 return vm_swappiness;
 655
 656         return memcg->swappiness;
 657 }
 658
 659 #else
 660 static inline int mem_cgroup_swappiness(struct mem_cgroup *mem)
 661 {
 662         return vm_swappiness;
 663 }
 664 #endif
 665
 666 #ifdef CONFIG_MEMCG_SWAP
 667 extern void mem_cgroup_swapout(struct page *page, swp_entry_t entry);
 668 extern int mem_cgroup_try_charge_swap(struct page *page, swp_entry_t entry);
 669 extern void mem_cgroup_uncharge_swap(swp_entry_t entry, unsigned int nr_pages);
 670 extern long mem_cgroup_get_nr_swap_pages(struct mem_cgroup *memcg);
 671 extern bool mem_cgroup_swap_full(struct page *page);
 672 #else
 673 static inline void mem_cgroup_swapout(struct page *page, swp_entry_t entry)
 674 {
 675 }
 676
 677 static inline int mem_cgroup_try_charge_swap(struct page *page,
 678                                              swp_entry_t entry)
 679 {
 680         return 0;
 681 }
 682
 683 static inline void mem_cgroup_uncharge_swap(swp_entry_t entry,
 684                                             unsigned int nr_pages)
 685 {
 686 }
 687
 688 static inline long mem_cgroup_get_nr_swap_pages(struct mem_cgroup *memcg)
 689 {
 690         return get_nr_swap_pages();
 691 }
 692
 693 static inline bool mem_cgroup_swap_full(struct page *page)
 694 {
 695         return vm_swap_full();
 696 }
 697 #endif
 698
 699 #endif /* __KERNEL__*/
 700 #endif /* _LINUX_SWAP_H */