include/linux/swap.h

   1 #ifndef _LINUX_SWAP_H
   2 #define _LINUX_SWAP_H
   3
   4 #include <linux/spinlock.h>
   5 #include <linux/linkage.h>
   6 #include <linux/mmzone.h>
   7 #include <linux/list.h>
   8 #include <linux/memcontrol.h>
   9 #include <linux/sched.h>
  10 #include <linux/node.h>
  11 #include <linux/fs.h>
  12 #include <linux/atomic.h>
  13 #include <linux/page-flags.h>
  14 #include <asm/page.h>
  15
  16 struct notifier_block;
  17
  18 struct bio;
  19
  20 #define SWAP_FLAG_PREFER        0x8000  /* set if swap priority specified */
  21 #define SWAP_FLAG_PRIO_MASK     0x7fff
  22 #define SWAP_FLAG_PRIO_SHIFT    0
  23 #define SWAP_FLAG_DISCARD       0x10000 /* enable discard for swap */
  24 #define SWAP_FLAG_DISCARD_ONCE  0x20000 /* discard swap area at swapon-time */
  25 #define SWAP_FLAG_DISCARD_PAGES 0x40000 /* discard page-clusters after use */
  26
  27 #define SWAP_FLAGS_VALID        (SWAP_FLAG_PRIO_MASK | SWAP_FLAG_PREFER | \
  28                                  SWAP_FLAG_DISCARD | SWAP_FLAG_DISCARD_ONCE | \
  29                                  SWAP_FLAG_DISCARD_PAGES)
  30
  31 static inline int current_is_kswapd(void)
  32 {
  33         return current->flags & PF_KSWAPD;
  34 }
  35
  36 /*
  37  * MAX_SWAPFILES defines the maximum number of swaptypes: things which can
  38  * be swapped to.  The swap type and the offset into that swap type are
  39  * encoded into pte's and into pgoff_t's in the swapcache.  Using five bits
  40  * for the type means that the maximum number of swapcache pages is 27 bits
  41  * on 32-bit-pgoff_t architectures.  And that assumes that the architecture packs
  42  * the type/offset into the pte as 5/27 as well.
  43  */
  44 #define MAX_SWAPFILES_SHIFT     5
  45
  46 /*
  47  * Use some of the swap files numbers for other purposes. This
  48  * is a convenient way to hook into the VM to trigger special
  49  * actions on faults.
  50  */
  51
  52 /*
  53  * NUMA node memory migration support
  54  */
  55 #ifdef CONFIG_MIGRATION
  56 #define SWP_MIGRATION_NUM 2
  57 #define SWP_MIGRATION_READ      (MAX_SWAPFILES + SWP_HWPOISON_NUM)
  58 #define SWP_MIGRATION_WRITE     (MAX_SWAPFILES + SWP_HWPOISON_NUM + 1)
  59 #else
  60 #define SWP_MIGRATION_NUM 0
  61 #endif
  62
  63 /*
  64  * Handling of hardware poisoned pages with memory corruption.
  65  */
  66 #ifdef CONFIG_MEMORY_FAILURE
  67 #define SWP_HWPOISON_NUM 1
  68 #define SWP_HWPOISON            MAX_SWAPFILES
  69 #else
  70 #define SWP_HWPOISON_NUM 0
  71 #endif
  72
  73 #define MAX_SWAPFILES \
  74         ((1 << MAX_SWAPFILES_SHIFT) - SWP_MIGRATION_NUM - SWP_HWPOISON_NUM)
  75
  76 /*
  77  * Magic header for a swap area. The first part of the union is
  78  * what the swap magic looks like for the old (limited to 128MB)
  79  * swap area format, the second part of the union adds - in the
  80  * old reserved area - some extra information. Note that the first
  81  * kilobyte is reserved for boot loader or disk label stuff...
  82  *
  83  * Having the magic at the end of the PAGE_SIZE makes detecting swap
  84  * areas somewhat tricky on machines that support multiple page sizes.
  85  * For 2.5 we'll probably want to move the magic to just beyond the
  86  * bootbits...
  87  */
  88 union swap_header {
  89         struct {
  90                 char reserved[PAGE_SIZE - 10];
  91                 char magic[10];                 /* SWAP-SPACE or SWAPSPACE2 */
  92         } magic;
  93         struct {
  94                 char            bootbits[1024]; /* Space for disklabel etc. */
  95                 __u32           version;
  96                 __u32           last_page;
  97                 __u32           nr_badpages;
  98                 unsigned char   sws_uuid[16];
  99                 unsigned char   sws_volume[16];
 100                 __u32           padding[117];
 101                 __u32           badpages[1];
 102         } info;
 103 };
 104
 105  /* A swap entry has to fit into a "unsigned long", as
 106   * the entry is hidden in the "index" field of the
 107   * swapper address space.
 108   */
 109 typedef struct {
 110         unsigned long val;
 111 } swp_entry_t;
 112
 113 /*
 114  * current->reclaim_state points to one of these when a task is running
 115  * memory reclaim
 116  */
 117 struct reclaim_state {
 118         unsigned long reclaimed_slab;
 119 };
 120
 121 #ifdef __KERNEL__
 122
 123 struct address_space;
 124 struct sysinfo;
 125 struct writeback_control;
 126 struct zone;
 127
 128 /*
 129  * A swap extent maps a range of a swapfile's PAGE_SIZE pages onto a range of
 130  * disk blocks.  A list of swap extents maps the entire swapfile.  (Where the
 131  * term `swapfile' refers to either a blockdevice or an IS_REG file.  Apart
 132  * from setup, they're handled identically.
 133  *
 134  * We always assume that blocks are of size PAGE_SIZE.
 135  */
 136 struct swap_extent {
 137         struct list_head list;
 138         pgoff_t start_page;
 139         pgoff_t nr_pages;
 140         sector_t start_block;
 141 };
 142
 143 /*
 144  * Max bad pages in the new format..
 145  */
 146 #define __swapoffset(x) ((unsigned long)&((union swap_header *)0)->x)
 147 #define MAX_SWAP_BADPAGES \
 148         ((__swapoffset(magic.magic) - __swapoffset(info.badpages)) / sizeof(int))
 149
 150 enum {
 151         SWP_USED        = (1 << 0),     /* is slot in swap_info[] used? */
 152         SWP_WRITEOK     = (1 << 1),     /* ok to write to this swap?    */
 153         SWP_DISCARDABLE = (1 << 2),     /* blkdev support discard */
 154         SWP_DISCARDING  = (1 << 3),     /* now discarding a free cluster */
 155         SWP_SOLIDSTATE  = (1 << 4),     /* blkdev seeks are cheap */
 156         SWP_CONTINUED   = (1 << 5),     /* swap_map has count continuation */
 157         SWP_BLKDEV      = (1 << 6),     /* its a block device */
 158         SWP_FILE        = (1 << 7),     /* set after swap_activate success */
 159         SWP_AREA_DISCARD = (1 << 8),    /* single-time swap area discards */
 160         SWP_PAGE_DISCARD = (1 << 9),    /* freed swap page-cluster discards */
 161                                         /* add others here before... */
 162         SWP_SCANNING    = (1 << 10),    /* refcount in scan_swap_map */
 163 };
 164
 165 #define SWAP_CLUSTER_MAX 32UL
 166 #define COMPACT_CLUSTER_MAX SWAP_CLUSTER_MAX
 167
 168 /*
 169  * Ratio between zone->managed_pages and the "gap" that above the per-zone
 170  * "high_wmark". While balancing nodes, We allow kswapd to shrink zones that
 171  * do not meet the (high_wmark + gap) watermark, even which already met the
 172  * high_wmark, in order to provide better per-zone lru behavior. We are ok to
 173  * spend not more than 1% of the memory for this zone balancing "gap".
 174  */
 175 #define KSWAPD_ZONE_BALANCE_GAP_RATIO 100
 176
 177 #define SWAP_MAP_MAX    0x3e    /* Max duplication count, in first swap_map */
 178 #define SWAP_MAP_BAD    0x3f    /* Note pageblock is bad, in first swap_map */
 179 #define SWAP_HAS_CACHE  0x40    /* Flag page is cached, in first swap_map */
 180 #define SWAP_CONT_MAX   0x7f    /* Max count, in each swap_map continuation */
 181 #define COUNT_CONTINUED 0x80    /* See swap_map continuation for full count */
 182 #define SWAP_MAP_SHMEM  0xbf    /* Owned by shmem/tmpfs, in first swap_map */
 183
 184 /*
 185  * We use this to track usage of a cluster. A cluster is a block of swap disk
 186  * space with SWAPFILE_CLUSTER pages long and naturally aligns in disk. All
 187  * free clusters are organized into a list. We fetch an entry from the list to
 188  * get a free cluster.
 189  *
 190  * The data field stores next cluster if the cluster is free or cluster usage
 191  * counter otherwise. The flags field determines if a cluster is free. This is
 192  * protected by swap_info_struct.lock.
 193  */
 194 struct swap_cluster_info {
 195         unsigned int data:24;
 196         unsigned int flags:8;
 197 };
 198 #define CLUSTER_FLAG_FREE 1 /* This cluster is free */
 199 #define CLUSTER_FLAG_NEXT_NULL 2 /* This cluster has no next cluster */
 200
 201 /*
 202  * We assign a cluster to each CPU, so each CPU can allocate swap entry from
 203  * its own cluster and swapout sequentially. The purpose is to optimize swapout
 204  * throughput.
 205  */
 206 struct percpu_cluster {
 207         struct swap_cluster_info index; /* Current cluster index */
 208         unsigned int next; /* Likely next allocation offset */
 209 };
 210
 211 /*
 212  * The in-memory structure used to track swap areas.
 213  */
 214 struct swap_info_struct {
 215         unsigned long   flags;          /* SWP_USED etc: see above */
 216         signed short    prio;           /* swap priority of this type */
 217         struct plist_node list;         /* entry in swap_active_head */
 218         struct plist_node avail_list;   /* entry in swap_avail_head */
 219         signed char     type;           /* strange name for an index */
 220         unsigned int    max;            /* extent of the swap_map */
 221         unsigned char *swap_map;        /* vmalloc'ed array of usage counts */
 222         struct swap_cluster_info *cluster_info; /* cluster info. Only for SSD */
 223         struct swap_cluster_info free_cluster_head; /* free cluster list head */
 224         struct swap_cluster_info free_cluster_tail; /* free cluster list tail */
 225         unsigned int lowest_bit;        /* index of first free in swap_map */
 226         unsigned int highest_bit;       /* index of last free in swap_map */
 227         unsigned int pages;             /* total of usable pages of swap */
 228         unsigned int inuse_pages;       /* number of those currently in use */
 229         unsigned int cluster_next;      /* likely index for next allocation */
 230         unsigned int cluster_nr;        /* countdown to next cluster search */
 231         struct percpu_cluster __percpu *percpu_cluster; /* per cpu's swap location */
 232         struct swap_extent *curr_swap_extent;
 233         struct swap_extent first_swap_extent;
 234         struct block_device *bdev;      /* swap device or bdev of swap file */
 235         struct file *swap_file;         /* seldom referenced */
 236         unsigned int old_block_size;    /* seldom referenced */
 237 #ifdef CONFIG_FRONTSWAP
 238         unsigned long *frontswap_map;   /* frontswap in-use, one bit per page */
 239         atomic_t frontswap_pages;       /* frontswap pages in-use counter */
 240 #endif
 241         spinlock_t lock;                /*
 242                                          * protect map scan related fields like
 243                                          * swap_map, lowest_bit, highest_bit,
 244                                          * inuse_pages, cluster_next,
 245                                          * cluster_nr, lowest_alloc,
 246                                          * highest_alloc, free/discard cluster
 247                                          * list. other fields are only changed
 248                                          * at swapon/swapoff, so are protected
 249                                          * by swap_lock. changing flags need
 250                                          * hold this lock and swap_lock. If
 251                                          * both locks need hold, hold swap_lock
 252                                          * first.
 253                                          */
 254         struct work_struct discard_work; /* discard worker */
 255         struct swap_cluster_info discard_cluster_head; /* list head of discard clusters */
 256         struct swap_cluster_info discard_cluster_tail; /* list tail of discard clusters */
 257 };
 258
 259 /* linux/mm/workingset.c */
 260 void *workingset_eviction(struct address_space *mapping, struct page *page);
 261 bool workingset_refault(void *shadow);
 262 void workingset_activation(struct page *page);
 263 extern struct list_lru workingset_shadow_nodes;
 264
 265 static inline unsigned int workingset_node_pages(struct radix_tree_node *node)
 266 {
 267         return node->count & RADIX_TREE_COUNT_MASK;
 268 }
 269
 270 static inline void workingset_node_pages_inc(struct radix_tree_node *node)
 271 {
 272         node->count++;
 273 }
 274
 275 static inline void workingset_node_pages_dec(struct radix_tree_node *node)
 276 {
 277         node->count--;
 278 }
 279
 280 static inline unsigned int workingset_node_shadows(struct radix_tree_node *node)
 281 {
 282         return node->count >> RADIX_TREE_COUNT_SHIFT;
 283 }
 284
 285 static inline void workingset_node_shadows_inc(struct radix_tree_node *node)
 286 {
 287         node->count += 1U << RADIX_TREE_COUNT_SHIFT;
 288 }
 289
 290 static inline void workingset_node_shadows_dec(struct radix_tree_node *node)
 291 {
 292         node->count -= 1U << RADIX_TREE_COUNT_SHIFT;
 293 }
 294
 295 /* linux/mm/page_alloc.c */
 296 extern unsigned long totalram_pages;
 297 extern unsigned long totalreserve_pages;
 298 extern unsigned long dirty_balance_reserve;
 299 extern unsigned long nr_free_buffer_pages(void);
 300 extern unsigned long nr_free_pagecache_pages(void);
 301
 302 /* Definition of global_page_state not available yet */
 303 #define nr_free_pages() global_page_state(NR_FREE_PAGES)
 304
 305
 306 /* linux/mm/swap.c */
 307 extern void lru_cache_add(struct page *);
 308 extern void lru_cache_add_anon(struct page *page);
 309 extern void lru_cache_add_file(struct page *page);
 310 extern void lru_add_page_tail(struct page *page, struct page *page_tail,
 311                          struct lruvec *lruvec, struct list_head *head);
 312 extern void activate_page(struct page *);
 313 extern void mark_page_accessed(struct page *);
 314 extern void lru_add_drain(void);
 315 extern void lru_add_drain_cpu(int cpu);
 316 extern void lru_add_drain_all(void);
 317 extern void rotate_reclaimable_page(struct page *page);
 318 extern void deactivate_page(struct page *page);
 319 extern void swap_setup(void);
 320
 321 extern void add_page_to_unevictable_list(struct page *page);
 322
 323 extern void lru_cache_add_active_or_unevictable(struct page *page,
 324                                                 struct vm_area_struct *vma);
 325
 326 /* linux/mm/vmscan.c */
 327 extern unsigned long try_to_free_pages(struct zonelist *zonelist, int order,
 328                                         gfp_t gfp_mask, nodemask_t *mask);
 329 extern int __isolate_lru_page(struct page *page, isolate_mode_t mode);
 330 extern unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *mem,
 331                                                   gfp_t gfp_mask, bool noswap);
 332 extern unsigned long mem_cgroup_shrink_node_zone(struct mem_cgroup *mem,
 333                                                 gfp_t gfp_mask, bool noswap,
 334                                                 struct zone *zone,
 335                                                 unsigned long *nr_scanned);
 336 extern unsigned long shrink_all_memory(unsigned long nr_pages);
 337 extern int vm_swappiness;
 338 extern int remove_mapping(struct address_space *mapping, struct page *page);
 339 extern unsigned long vm_total_pages;
 340
 341 #ifdef CONFIG_NUMA
 342 extern int zone_reclaim_mode;
 343 extern int sysctl_min_unmapped_ratio;
 344 extern int sysctl_min_slab_ratio;
 345 extern int zone_reclaim(struct zone *, gfp_t, unsigned int);
 346 #else
 347 #define zone_reclaim_mode 0
 348 static inline int zone_reclaim(struct zone *z, gfp_t mask, unsigned int order)
 349 {
 350         return 0;
 351 }
 352 #endif
 353
 354 extern int page_evictable(struct page *page);
 355 extern void check_move_unevictable_pages(struct page **, int nr_pages);
 356
 357 extern unsigned long scan_unevictable_pages;
 358 extern int scan_unevictable_handler(struct ctl_table *, int,
 359                                         void __user *, size_t *, loff_t *);
 360 #ifdef CONFIG_NUMA
 361 extern int scan_unevictable_register_node(struct node *node);
 362 extern void scan_unevictable_unregister_node(struct node *node);
 363 #else
 364 static inline int scan_unevictable_register_node(struct node *node)
 365 {
 366         return 0;
 367 }
 368 static inline void scan_unevictable_unregister_node(struct node *node)
 369 {
 370 }
 371 #endif
 372
 373 extern int kswapd_run(int nid);
 374 extern void kswapd_stop(int nid);
 375 #ifdef CONFIG_MEMCG
 376 extern int mem_cgroup_swappiness(struct mem_cgroup *mem);
 377 #else
 378 static inline int mem_cgroup_swappiness(struct mem_cgroup *mem)
 379 {
 380         return vm_swappiness;
 381 }
 382 #endif
 383 #ifdef CONFIG_MEMCG_SWAP
 384 extern void mem_cgroup_swapout(struct page *page, swp_entry_t entry);
 385 extern void mem_cgroup_uncharge_swap(swp_entry_t entry);
 386 #else
 387 static inline void mem_cgroup_swapout(struct page *page, swp_entry_t entry)
 388 {
 389 }
 390 static inline void mem_cgroup_uncharge_swap(swp_entry_t entry)
 391 {
 392 }
 393 #endif
 394 #ifdef CONFIG_SWAP
 395 /* linux/mm/page_io.c */
 396 extern int swap_readpage(struct page *);
 397 extern int swap_writepage(struct page *page, struct writeback_control *wbc);
 398 extern void end_swap_bio_write(struct bio *bio, int err);
 399 extern int __swap_writepage(struct page *page, struct writeback_control *wbc,
 400         void (*end_write_func)(struct bio *, int));
 401 extern int swap_set_page_dirty(struct page *page);
 402 extern void end_swap_bio_read(struct bio *bio, int err);
 403
 404 int add_swap_extent(struct swap_info_struct *sis, unsigned long start_page,
 405                 unsigned long nr_pages, sector_t start_block);
 406 int generic_swapfile_activate(struct swap_info_struct *, struct file *,
 407                 sector_t *);
 408
 409 /* linux/mm/swap_state.c */
 410 extern struct address_space swapper_spaces[];
 411 #define swap_address_space(entry) (&swapper_spaces[swp_type(entry)])
 412 extern unsigned long total_swapcache_pages(void);
 413 extern void show_swap_cache_info(void);
 414 extern int add_to_swap(struct page *, struct list_head *list);
 415 extern int add_to_swap_cache(struct page *, swp_entry_t, gfp_t);
 416 extern int __add_to_swap_cache(struct page *page, swp_entry_t entry);
 417 extern void __delete_from_swap_cache(struct page *);
 418 extern void delete_from_swap_cache(struct page *);
 419 extern void free_page_and_swap_cache(struct page *);
 420 extern void free_pages_and_swap_cache(struct page **, int);
 421 extern struct page *lookup_swap_cache(swp_entry_t);
 422 extern struct page *read_swap_cache_async(swp_entry_t, gfp_t,
 423                         struct vm_area_struct *vma, unsigned long addr);
 424 extern struct page *swapin_readahead(swp_entry_t, gfp_t,
 425                         struct vm_area_struct *vma, unsigned long addr);
 426
 427 /* linux/mm/swapfile.c */
 428 extern atomic_long_t nr_swap_pages;
 429 extern long total_swap_pages;
 430
 431 /* Swap 50% full? Release swapcache more aggressively.. */
 432 static inline bool vm_swap_full(void)
 433 {
 434         return atomic_long_read(&nr_swap_pages) * 2 < total_swap_pages;
 435 }
 436
 437 static inline long get_nr_swap_pages(void)
 438 {
 439         return atomic_long_read(&nr_swap_pages);
 440 }
 441
 442 extern void si_swapinfo(struct sysinfo *);
 443 extern swp_entry_t get_swap_page(void);
 444 extern swp_entry_t get_swap_page_of_type(int);
 445 extern int add_swap_count_continuation(swp_entry_t, gfp_t);
 446 extern void swap_shmem_alloc(swp_entry_t);
 447 extern int swap_duplicate(swp_entry_t);
 448 extern int swapcache_prepare(swp_entry_t);
 449 extern void swap_free(swp_entry_t);
 450 extern void swapcache_free(swp_entry_t);
 451 extern int free_swap_and_cache(swp_entry_t);
 452 extern int swap_type_of(dev_t, sector_t, struct block_device **);
 453 extern unsigned int count_swap_pages(int, int);
 454 extern sector_t map_swap_page(struct page *, struct block_device **);
 455 extern sector_t swapdev_block(int, pgoff_t);
 456 extern int page_swapcount(struct page *);
 457 extern struct swap_info_struct *page_swap_info(struct page *);
 458 extern int reuse_swap_page(struct page *);
 459 extern int try_to_free_swap(struct page *);
 460 struct backing_dev_info;
 461
 462 #ifdef CONFIG_MEMCG
 463 extern void
 464 mem_cgroup_uncharge_swapcache(struct page *page, swp_entry_t ent, bool swapout);
 465 #else
 466 static inline void
 467 mem_cgroup_uncharge_swapcache(struct page *page, swp_entry_t ent, bool swapout)
 468 {
 469 }
 470 #endif
 471
 472 #else /* CONFIG_SWAP */
 473
 474 #define swap_address_space(entry)               (NULL)
 475 #define get_nr_swap_pages()                     0L
 476 #define total_swap_pages                        0L
 477 #define total_swapcache_pages()                 0UL
 478 #define vm_swap_full()                          0
 479
 480 #define si_swapinfo(val) \
 481         do { (val)->freeswap = (val)->totalswap = 0; } while (0)
 482 /* only sparc can not include linux/pagemap.h in this file
 483  * so leave page_cache_release and release_pages undeclared... */
 484 #define free_page_and_swap_cache(page) \
 485         page_cache_release(page)
 486 #define free_pages_and_swap_cache(pages, nr) \
 487         release_pages((pages), (nr), false);
 488
 489 static inline void show_swap_cache_info(void)
 490 {
 491 }
 492
 493 #define free_swap_and_cache(swp)        is_migration_entry(swp)
 494 #define swapcache_prepare(swp)          is_migration_entry(swp)
 495
 496 static inline int add_swap_count_continuation(swp_entry_t swp, gfp_t gfp_mask)
 497 {
 498         return 0;
 499 }
 500
 501 static inline void swap_shmem_alloc(swp_entry_t swp)
 502 {
 503 }
 504
 505 static inline int swap_duplicate(swp_entry_t swp)
 506 {
 507         return 0;
 508 }
 509
 510 static inline void swap_free(swp_entry_t swp)
 511 {
 512 }
 513
 514 static inline void swapcache_free(swp_entry_t swp)
 515 {
 516 }
 517
 518 static inline struct page *swapin_readahead(swp_entry_t swp, gfp_t gfp_mask,
 519                         struct vm_area_struct *vma, unsigned long addr)
 520 {
 521         return NULL;
 522 }
 523
 524 static inline int swap_writepage(struct page *p, struct writeback_control *wbc)
 525 {
 526         return 0;
 527 }
 528
 529 static inline struct page *lookup_swap_cache(swp_entry_t swp)
 530 {
 531         return NULL;
 532 }
 533
 534 static inline int add_to_swap(struct page *page, struct list_head *list)
 535 {
 536         return 0;
 537 }
 538
 539 static inline int add_to_swap_cache(struct page *page, swp_entry_t entry,
 540                                                         gfp_t gfp_mask)
 541 {
 542         return -1;
 543 }
 544
 545 static inline void __delete_from_swap_cache(struct page *page)
 546 {
 547 }
 548
 549 static inline void delete_from_swap_cache(struct page *page)
 550 {
 551 }
 552
 553 static inline int page_swapcount(struct page *page)
 554 {
 555         return 0;
 556 }
 557
 558 #define reuse_swap_page(page)   (page_mapcount(page) == 1)
 559
 560 static inline int try_to_free_swap(struct page *page)
 561 {
 562         return 0;
 563 }
 564
 565 static inline swp_entry_t get_swap_page(void)
 566 {
 567         swp_entry_t entry;
 568         entry.val = 0;
 569         return entry;
 570 }
 571
 572 static inline void
 573 mem_cgroup_uncharge_swapcache(struct page *page, swp_entry_t ent)
 574 {
 575 }
 576
 577 #endif /* CONFIG_SWAP */
 578 #endif /* __KERNEL__*/
 579 #endif /* _LINUX_SWAP_H */