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 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[]; /*
 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, struct mem_cgroup *target_memcg);
 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 deactivate_page(struct page *page);
 344 extern void mark_page_lazyfree(struct page *page);
 345 extern void swap_setup(void);
 346
 347 extern void lru_cache_add_active_or_unevictable(struct page *page,
 348                                                 struct vm_area_struct *vma);
 349
 350 /* linux/mm/vmscan.c */
 351 extern unsigned long zone_reclaimable_pages(struct zone *zone);
 352 extern unsigned long try_to_free_pages(struct zonelist *zonelist, int order,
 353                                         gfp_t gfp_mask, nodemask_t *mask);
 354 extern int __isolate_lru_page(struct page *page, isolate_mode_t mode);
 355 extern unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *memcg,
 356                                                   unsigned long nr_pages,
 357                                                   gfp_t gfp_mask,
 358                                                   bool may_swap);
 359 extern unsigned long mem_cgroup_shrink_node(struct mem_cgroup *mem,
 360                                                 gfp_t gfp_mask, bool noswap,
 361                                                 pg_data_t *pgdat,
 362                                                 unsigned long *nr_scanned);
 363 extern unsigned long shrink_all_memory(unsigned long nr_pages);
 364 extern int vm_swappiness;
 365 extern int remove_mapping(struct address_space *mapping, struct page *page);
 366 extern unsigned long vm_total_pages;
 367
 368 extern unsigned long reclaim_pages(struct list_head *page_list);
 369 #ifdef CONFIG_NUMA
 370 extern int node_reclaim_mode;
 371 extern int sysctl_min_unmapped_ratio;
 372 extern int sysctl_min_slab_ratio;
 373 #else
 374 #define node_reclaim_mode 0
 375 #endif
 376
 377 extern void check_move_unevictable_pages(struct pagevec *pvec);
 378
 379 extern int kswapd_run(int nid);
 380 extern void kswapd_stop(int nid);
 381
 382 #ifdef CONFIG_SWAP
 383
 384 #include <linux/blk_types.h> /* for bio_end_io_t */
 385
 386 /* linux/mm/page_io.c */
 387 extern int swap_readpage(struct page *page, bool do_poll);
 388 extern int swap_writepage(struct page *page, struct writeback_control *wbc);
 389 extern void end_swap_bio_write(struct bio *bio);
 390 extern int __swap_writepage(struct page *page, struct writeback_control *wbc,
 391         bio_end_io_t end_write_func);
 392 extern int swap_set_page_dirty(struct page *page);
 393
 394 int add_swap_extent(struct swap_info_struct *sis, unsigned long start_page,
 395                 unsigned long nr_pages, sector_t start_block);
 396 int generic_swapfile_activate(struct swap_info_struct *, struct file *,
 397                 sector_t *);
 398
 399 /* linux/mm/swap_state.c */
 400 /* One swap address space for each 64M swap space */
 401 #define SWAP_ADDRESS_SPACE_SHIFT        14
 402 #define SWAP_ADDRESS_SPACE_PAGES        (1 << SWAP_ADDRESS_SPACE_SHIFT)
 403 extern struct address_space *swapper_spaces[];
 404 #define swap_address_space(entry)                           \
 405         (&swapper_spaces[swp_type(entry)][swp_offset(entry) \
 406                 >> SWAP_ADDRESS_SPACE_SHIFT])
 407 extern unsigned long total_swapcache_pages(void);
 408 extern void show_swap_cache_info(void);
 409 extern int add_to_swap(struct page *page);
 410 extern int add_to_swap_cache(struct page *, swp_entry_t, gfp_t);
 411 extern int __add_to_swap_cache(struct page *page, swp_entry_t entry);
 412 extern void __delete_from_swap_cache(struct page *, swp_entry_t entry);
 413 extern void delete_from_swap_cache(struct page *);
 414 extern void free_page_and_swap_cache(struct page *);
 415 extern void free_pages_and_swap_cache(struct page **, int);
 416 extern struct page *lookup_swap_cache(swp_entry_t entry,
 417                                       struct vm_area_struct *vma,
 418                                       unsigned long addr);
 419 extern struct page *read_swap_cache_async(swp_entry_t, gfp_t,
 420                         struct vm_area_struct *vma, unsigned long addr,
 421                         bool do_poll);
 422 extern struct page *__read_swap_cache_async(swp_entry_t, gfp_t,
 423                         struct vm_area_struct *vma, unsigned long addr,
 424                         bool *new_page_allocated);
 425 extern struct page *swap_cluster_readahead(swp_entry_t entry, gfp_t flag,
 426                                 struct vm_fault *vmf);
 427 extern struct page *swapin_readahead(swp_entry_t entry, gfp_t flag,
 428                                 struct vm_fault *vmf);
 429
 430 /* linux/mm/swapfile.c */
 431 extern atomic_long_t nr_swap_pages;
 432 extern long total_swap_pages;
 433 extern atomic_t nr_rotate_swap;
 434 extern bool has_usable_swap(void);
 435
 436 /* Swap 50% full? Release swapcache more aggressively.. */
 437 static inline bool vm_swap_full(void)
 438 {
 439         return atomic_long_read(&nr_swap_pages) * 2 < total_swap_pages;
 440 }
 441
 442 static inline long get_nr_swap_pages(void)
 443 {
 444         return atomic_long_read(&nr_swap_pages);
 445 }
 446
 447 extern void si_swapinfo(struct sysinfo *);
 448 extern swp_entry_t get_swap_page(struct page *page);
 449 extern void put_swap_page(struct page *page, swp_entry_t entry);
 450 extern swp_entry_t get_swap_page_of_type(int);
 451 extern int get_swap_pages(int n, swp_entry_t swp_entries[], int entry_size);
 452 extern int add_swap_count_continuation(swp_entry_t, gfp_t);
 453 extern void swap_shmem_alloc(swp_entry_t);
 454 extern int swap_duplicate(swp_entry_t);
 455 extern int swapcache_prepare(swp_entry_t);
 456 extern void swap_free(swp_entry_t);
 457 extern void swapcache_free_entries(swp_entry_t *entries, int n);
 458 extern int free_swap_and_cache(swp_entry_t);
 459 extern int swap_type_of(dev_t, sector_t, struct block_device **);
 460 extern unsigned int count_swap_pages(int, int);
 461 extern sector_t map_swap_page(struct page *, struct block_device **);
 462 extern sector_t swapdev_block(int, pgoff_t);
 463 extern int page_swapcount(struct page *);
 464 extern int __swap_count(swp_entry_t entry);
 465 extern int __swp_swapcount(swp_entry_t entry);
 466 extern int swp_swapcount(swp_entry_t entry);
 467 extern struct swap_info_struct *page_swap_info(struct page *);
 468 extern struct swap_info_struct *swp_swap_info(swp_entry_t entry);
 469 extern bool reuse_swap_page(struct page *, int *);
 470 extern int try_to_free_swap(struct page *);
 471 struct backing_dev_info;
 472 extern int init_swap_address_space(unsigned int type, unsigned long nr_pages);
 473 extern void exit_swap_address_space(unsigned int type);
 474 extern struct swap_info_struct *get_swap_device(swp_entry_t entry);
 475
 476 static inline void put_swap_device(struct swap_info_struct *si)
 477 {
 478         rcu_read_unlock();
 479 }
 480
 481 #else /* CONFIG_SWAP */
 482
 483 static inline int swap_readpage(struct page *page, bool do_poll)
 484 {
 485         return 0;
 486 }
 487
 488 static inline struct swap_info_struct *swp_swap_info(swp_entry_t entry)
 489 {
 490         return NULL;
 491 }
 492
 493 #define swap_address_space(entry)               (NULL)
 494 #define get_nr_swap_pages()                     0L
 495 #define total_swap_pages                        0L
 496 #define total_swapcache_pages()                 0UL
 497 #define vm_swap_full()                          0
 498
 499 #define si_swapinfo(val) \
 500         do { (val)->freeswap = (val)->totalswap = 0; } while (0)
 501 /* only sparc can not include linux/pagemap.h in this file
 502  * so leave put_page and release_pages undeclared... */
 503 #define free_page_and_swap_cache(page) \
 504         put_page(page)
 505 #define free_pages_and_swap_cache(pages, nr) \
 506         release_pages((pages), (nr));
 507
 508 static inline void show_swap_cache_info(void)
 509 {
 510 }
 511
 512 #define free_swap_and_cache(e) ({(is_migration_entry(e) || is_device_private_entry(e));})
 513 #define swapcache_prepare(e) ({(is_migration_entry(e) || is_device_private_entry(e));})
 514
 515 static inline int add_swap_count_continuation(swp_entry_t swp, gfp_t gfp_mask)
 516 {
 517         return 0;
 518 }
 519
 520 static inline void swap_shmem_alloc(swp_entry_t swp)
 521 {
 522 }
 523
 524 static inline int swap_duplicate(swp_entry_t swp)
 525 {
 526         return 0;
 527 }
 528
 529 static inline void swap_free(swp_entry_t swp)
 530 {
 531 }
 532
 533 static inline void put_swap_page(struct page *page, swp_entry_t swp)
 534 {
 535 }
 536
 537 static inline struct page *swap_cluster_readahead(swp_entry_t entry,
 538                                 gfp_t gfp_mask, struct vm_fault *vmf)
 539 {
 540         return NULL;
 541 }
 542
 543 static inline struct page *swapin_readahead(swp_entry_t swp, gfp_t gfp_mask,
 544                         struct vm_fault *vmf)
 545 {
 546         return NULL;
 547 }
 548
 549 static inline int swap_writepage(struct page *p, struct writeback_control *wbc)
 550 {
 551         return 0;
 552 }
 553
 554 static inline struct page *lookup_swap_cache(swp_entry_t swp,
 555                                              struct vm_area_struct *vma,
 556                                              unsigned long addr)
 557 {
 558         return NULL;
 559 }
 560
 561 static inline int add_to_swap(struct page *page)
 562 {
 563         return 0;
 564 }
 565
 566 static inline int add_to_swap_cache(struct page *page, swp_entry_t entry,
 567                                                         gfp_t gfp_mask)
 568 {
 569         return -1;
 570 }
 571
 572 static inline void __delete_from_swap_cache(struct page *page,
 573                                                         swp_entry_t entry)
 574 {
 575 }
 576
 577 static inline void delete_from_swap_cache(struct page *page)
 578 {
 579 }
 580
 581 static inline int page_swapcount(struct page *page)
 582 {
 583         return 0;
 584 }
 585
 586 static inline int __swap_count(swp_entry_t entry)
 587 {
 588         return 0;
 589 }
 590
 591 static inline int __swp_swapcount(swp_entry_t entry)
 592 {
 593         return 0;
 594 }
 595
 596 static inline int swp_swapcount(swp_entry_t entry)
 597 {
 598         return 0;
 599 }
 600
 601 #define reuse_swap_page(page, total_map_swapcount) \
 602         (page_trans_huge_mapcount(page, total_map_swapcount) == 1)
 603
 604 static inline int try_to_free_swap(struct page *page)
 605 {
 606         return 0;
 607 }
 608
 609 static inline swp_entry_t get_swap_page(struct page *page)
 610 {
 611         swp_entry_t entry;
 612         entry.val = 0;
 613         return entry;
 614 }
 615
 616 #endif /* CONFIG_SWAP */
 617
 618 #ifdef CONFIG_THP_SWAP
 619 extern int split_swap_cluster(swp_entry_t entry);
 620 #else
 621 static inline int split_swap_cluster(swp_entry_t entry)
 622 {
 623         return 0;
 624 }
 625 #endif
 626
 627 #ifdef CONFIG_MEMCG
 628 static inline int mem_cgroup_swappiness(struct mem_cgroup *memcg)
 629 {
 630         /* Cgroup2 doesn't have per-cgroup swappiness */
 631         if (cgroup_subsys_on_dfl(memory_cgrp_subsys))
 632                 return vm_swappiness;
 633
 634         /* root ? */
 635         if (mem_cgroup_disabled() || mem_cgroup_is_root(memcg))
 636                 return vm_swappiness;
 637
 638         return memcg->swappiness;
 639 }
 640 #else
 641 static inline int mem_cgroup_swappiness(struct mem_cgroup *mem)
 642 {
 643         return vm_swappiness;
 644 }
 645 #endif
 646
 647 #if defined(CONFIG_SWAP) && defined(CONFIG_MEMCG) && defined(CONFIG_BLK_CGROUP)
 648 extern void mem_cgroup_throttle_swaprate(struct mem_cgroup *memcg, int node,
 649                                          gfp_t gfp_mask);
 650 #else
 651 static inline void mem_cgroup_throttle_swaprate(struct mem_cgroup *memcg,
 652                                                 int node, gfp_t gfp_mask)
 653 {
 654 }
 655 #endif
 656
 657 #ifdef CONFIG_MEMCG_SWAP
 658 extern void mem_cgroup_swapout(struct page *page, swp_entry_t entry);
 659 extern int mem_cgroup_try_charge_swap(struct page *page, swp_entry_t entry);
 660 extern void mem_cgroup_uncharge_swap(swp_entry_t entry, unsigned int nr_pages);
 661 extern long mem_cgroup_get_nr_swap_pages(struct mem_cgroup *memcg);
 662 extern bool mem_cgroup_swap_full(struct page *page);
 663 #else
 664 static inline void mem_cgroup_swapout(struct page *page, swp_entry_t entry)
 665 {
 666 }
 667
 668 static inline int mem_cgroup_try_charge_swap(struct page *page,
 669                                              swp_entry_t entry)
 670 {
 671         return 0;
 672 }
 673
 674 static inline void mem_cgroup_uncharge_swap(swp_entry_t entry,
 675                                             unsigned int nr_pages)
 676 {
 677 }
 678
 679 static inline long mem_cgroup_get_nr_swap_pages(struct mem_cgroup *memcg)
 680 {
 681         return get_nr_swap_pages();
 682 }
 683
 684 static inline bool mem_cgroup_swap_full(struct page *page)
 685 {
 686         return vm_swap_full();
 687 }
 688 #endif
 689
 690 #endif /* __KERNEL__*/
 691 #endif /* _LINUX_SWAP_H */