#ifndef _LINUX_SWAP_H
  #define _LINUX_SWAP_H

  #include <linux/spinlock.h>
  #include <linux/linkage.h>
  #include <linux/mmzone.h>
  #include <linux/list.h>

  #include <linux/memcontrol.h>

  #include <linux/sched.h>

  #include <linux/node.h>

  #include <asm/atomic.h>
  #include <asm/page.h>

  struct notifier_block;

  struct bio;

  #define SWAP_FLAG_PREFER	0x8000	/* set if swap priority specified */
  #define SWAP_FLAG_PRIO_MASK	0x7fff
  #define SWAP_FLAG_PRIO_SHIFT	0
  
  static inline int current_is_kswapd(void)
  {
  	return current->flags & PF_KSWAPD;
  }
  
  /*
   * MAX_SWAPFILES defines the maximum number of swaptypes: things which can
   * be swapped to.  The swap type and the offset into that swap type are
   * encoded into pte's and into pgoff_t's in the swapcache.  Using five bits
   * for the type means that the maximum number of swapcache pages is 27 bits
   * on 32-bit-pgoff_t architectures.  And that assumes that the architecture packs
   * the type/offset into the pte as 5/27 as well.
   */
  #define MAX_SWAPFILES_SHIFT	5

  #ifndef CONFIG_MIGRATION

  #define MAX_SWAPFILES		(1 << MAX_SWAPFILES_SHIFT)

  #else
  /* Use last two entries for page migration swap entries */
  #define MAX_SWAPFILES		((1 << MAX_SWAPFILES_SHIFT)-2)
  #define SWP_MIGRATION_READ	MAX_SWAPFILES
  #define SWP_MIGRATION_WRITE	(MAX_SWAPFILES + 1)
  #endif

  
  /*
   * Magic header for a swap area. The first part of the union is
   * what the swap magic looks like for the old (limited to 128MB)
   * swap area format, the second part of the union adds - in the
   * old reserved area - some extra information. Note that the first
   * kilobyte is reserved for boot loader or disk label stuff...
   *
   * Having the magic at the end of the PAGE_SIZE makes detecting swap
   * areas somewhat tricky on machines that support multiple page sizes.
   * For 2.5 we'll probably want to move the magic to just beyond the
   * bootbits...
   */
  union swap_header {
  	struct {
  		char reserved[PAGE_SIZE - 10];
  		char magic[10];			/* SWAP-SPACE or SWAPSPACE2 */
  	} magic;
  	struct {

  		char		bootbits[1024];	/* Space for disklabel etc. */
  		__u32		version;
  		__u32		last_page;
  		__u32		nr_badpages;
  		unsigned char	sws_uuid[16];
  		unsigned char	sws_volume[16];
  		__u32		padding[117];
  		__u32		badpages[1];

  	} info;
  };
  
   /* A swap entry has to fit into a "unsigned long", as
    * the entry is hidden in the "index" field of the
    * swapper address space.
    */
  typedef struct {
  	unsigned long val;
  } swp_entry_t;
  
  /*
   * current->reclaim_state points to one of these when a task is running
   * memory reclaim
   */
  struct reclaim_state {
  	unsigned long reclaimed_slab;
  };
  
  #ifdef __KERNEL__
  
  struct address_space;
  struct sysinfo;
  struct writeback_control;
  struct zone;
  
  /*
   * A swap extent maps a range of a swapfile's PAGE_SIZE pages onto a range of
   * disk blocks.  A list of swap extents maps the entire swapfile.  (Where the
   * term `swapfile' refers to either a blockdevice or an IS_REG file.  Apart
   * from setup, they're handled identically.
   *
   * We always assume that blocks are of size PAGE_SIZE.
   */
  struct swap_extent {
  	struct list_head list;
  	pgoff_t start_page;
  	pgoff_t nr_pages;
  	sector_t start_block;
  };
  
  /*
   * Max bad pages in the new format..
   */
  #define __swapoffset(x) ((unsigned long)&((union swap_header *)0)->x)
  #define MAX_SWAP_BADPAGES \
  	((__swapoffset(magic.magic) - __swapoffset(info.badpages)) / sizeof(int))
  
  enum {
  	SWP_USED	= (1 << 0),	/* is slot in swap_info[] used? */
  	SWP_WRITEOK	= (1 << 1),	/* ok to write to this swap?	*/

  	SWP_DISCARDABLE = (1 << 2),	/* blkdev supports discard */

  	SWP_DISCARDING	= (1 << 3),	/* now discarding a free cluster */

  	SWP_SOLIDSTATE	= (1 << 4),	/* blkdev seeks are cheap */

  					/* add others here before... */
  	SWP_SCANNING	= (1 << 8),	/* refcount in scan_swap_map */

  };
  
  #define SWAP_CLUSTER_MAX 32
  
  #define SWAP_MAP_MAX	0x7fff
  #define SWAP_MAP_BAD	0x8000
  
  /*
   * The in-memory structure used to track swap areas.

   */
  struct swap_info_struct {

  	unsigned long flags;

  	int prio;			/* swap priority */

  	int next;			/* next entry on swap list */

  	struct file *swap_file;
  	struct block_device *bdev;
  	struct list_head extent_list;

  	struct swap_extent *curr_swap_extent;

  	unsigned short *swap_map;

  	unsigned int lowest_bit;
  	unsigned int highest_bit;

  	unsigned int lowest_alloc;	/* while preparing discard cluster */
  	unsigned int highest_alloc;	/* while preparing discard cluster */

  	unsigned int cluster_next;
  	unsigned int cluster_nr;

  	unsigned int pages;
  	unsigned int max;
  	unsigned int inuse_pages;

  	unsigned int old_block_size;

  };
  
  struct swap_list_t {
  	int head;	/* head of priority-ordered swapfile list */
  	int next;	/* swapfile to be used next */
  };
  
  /* Swap 50% full? Release swapcache more aggressively.. */
  #define vm_swap_full() (nr_swap_pages*2 < total_swap_pages)

  /* linux/mm/page_alloc.c */
  extern unsigned long totalram_pages;

  extern unsigned long totalreserve_pages;

  extern unsigned int nr_free_buffer_pages(void);
  extern unsigned int nr_free_pagecache_pages(void);

  /* Definition of global_page_state not available yet */
  #define nr_free_pages() global_page_state(NR_FREE_PAGES)

  /* linux/mm/swap.c */

  extern void __lru_cache_add(struct page *, enum lru_list lru);
  extern void lru_cache_add_lru(struct page *, enum lru_list lru);

  extern void activate_page(struct page *);
  extern void mark_page_accessed(struct page *);

  extern void lru_add_drain(void);

  extern int lru_add_drain_all(void);

  extern void rotate_reclaimable_page(struct page *page);

  extern void swap_setup(void);

  extern void add_page_to_unevictable_list(struct page *page);

  /**
   * lru_cache_add: add a page to the page lists
   * @page: the page to add
   */

  static inline void lru_cache_add_anon(struct page *page)

  {

  	__lru_cache_add(page, LRU_INACTIVE_ANON);

  }

  static inline void lru_cache_add_active_anon(struct page *page)

  {

  	__lru_cache_add(page, LRU_ACTIVE_ANON);
  }
  
  static inline void lru_cache_add_file(struct page *page)
  {
  	__lru_cache_add(page, LRU_INACTIVE_FILE);
  }
  
  static inline void lru_cache_add_active_file(struct page *page)
  {
  	__lru_cache_add(page, LRU_ACTIVE_FILE);

  }

  /* linux/mm/vmscan.c */

  extern unsigned long try_to_free_pages(struct zonelist *zonelist, int order,

  					gfp_t gfp_mask);

  extern unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *mem,
  							gfp_t gfp_mask);

  extern int __isolate_lru_page(struct page *page, int mode, int file);

  extern unsigned long shrink_all_memory(unsigned long nr_pages);

  extern int vm_swappiness;

  extern int remove_mapping(struct address_space *mapping, struct page *page);

  extern long vm_total_pages;

  #ifdef CONFIG_NUMA
  extern int zone_reclaim_mode;

  extern int sysctl_min_unmapped_ratio;

  extern int sysctl_min_slab_ratio;

  extern int zone_reclaim(struct zone *, gfp_t, unsigned int);
  #else
  #define zone_reclaim_mode 0
  static inline int zone_reclaim(struct zone *z, gfp_t mask, unsigned int order)
  {
  	return 0;
  }
  #endif

  #ifdef CONFIG_UNEVICTABLE_LRU
  extern int page_evictable(struct page *page, struct vm_area_struct *vma);

  extern void scan_mapping_unevictable_pages(struct address_space *);

  
  extern unsigned long scan_unevictable_pages;
  extern int scan_unevictable_handler(struct ctl_table *, int, struct file *,
  					void __user *, size_t *, loff_t *);
  extern int scan_unevictable_register_node(struct node *node);
  extern void scan_unevictable_unregister_node(struct node *node);

  #else
  static inline int page_evictable(struct page *page,
  						struct vm_area_struct *vma)
  {
  	return 1;
  }

  static inline void scan_mapping_unevictable_pages(struct address_space *mapping)
  {
  }

  
  static inline int scan_unevictable_register_node(struct node *node)
  {
  	return 0;
  }
  
  static inline void scan_unevictable_unregister_node(struct node *node) { }

  #endif

  extern int kswapd_run(int nid);

  #ifdef CONFIG_MMU
  /* linux/mm/shmem.c */
  extern int shmem_unuse(swp_entry_t entry, struct page *page);
  #endif /* CONFIG_MMU */
  
  extern void swap_unplug_io_fn(struct backing_dev_info *, struct page *);
  
  #ifdef CONFIG_SWAP
  /* linux/mm/page_io.c */
  extern int swap_readpage(struct file *, struct page *);
  extern int swap_writepage(struct page *page, struct writeback_control *wbc);

  extern void end_swap_bio_read(struct bio *bio, int err);

  
  /* linux/mm/swap_state.c */
  extern struct address_space swapper_space;
  #define total_swapcache_pages  swapper_space.nrpages
  extern void show_swap_cache_info(void);

  extern int add_to_swap(struct page *);

  extern int add_to_swap_cache(struct page *, swp_entry_t, gfp_t);

  extern void __delete_from_swap_cache(struct page *);
  extern void delete_from_swap_cache(struct page *);

  extern void free_page_and_swap_cache(struct page *);
  extern void free_pages_and_swap_cache(struct page **, int);

  extern struct page *lookup_swap_cache(swp_entry_t);

  extern struct page *read_swap_cache_async(swp_entry_t, gfp_t,

  			struct vm_area_struct *vma, unsigned long addr);

  extern struct page *swapin_readahead(swp_entry_t, gfp_t,

  			struct vm_area_struct *vma, unsigned long addr);

  /* linux/mm/swapfile.c */

  extern long nr_swap_pages;

  extern long total_swap_pages;

  extern void si_swapinfo(struct sysinfo *);
  extern swp_entry_t get_swap_page(void);

  extern swp_entry_t get_swap_page_of_type(int);

  extern int swap_duplicate(swp_entry_t);
  extern int valid_swaphandles(swp_entry_t, unsigned long *);
  extern void swap_free(swp_entry_t);

  extern int free_swap_and_cache(swp_entry_t);

  extern int swap_type_of(dev_t, sector_t, struct block_device **);

  extern unsigned int count_swap_pages(int, int);

  extern sector_t map_swap_page(struct swap_info_struct *, pgoff_t);

  extern sector_t swapdev_block(int, pgoff_t);

  extern struct swap_info_struct *get_swap_info_struct(unsigned);

  extern int reuse_swap_page(struct page *);

  extern int try_to_free_swap(struct page *);

  struct backing_dev_info;

  /* linux/mm/thrash.c */
  extern struct mm_struct * swap_token_mm;

  extern void grab_swap_token(void);
  extern void __put_swap_token(struct mm_struct *);
  
  static inline int has_swap_token(struct mm_struct *mm)
  {
  	return (mm == swap_token_mm);
  }
  
  static inline void put_swap_token(struct mm_struct *mm)
  {
  	if (has_swap_token(mm))
  		__put_swap_token(mm);
  }

  static inline void disable_swap_token(void)
  {
  	put_swap_token(swap_token_mm);
  }

  #else /* CONFIG_SWAP */

  #define nr_swap_pages				0L
  #define total_swap_pages			0L

  #define total_swapcache_pages			0UL
  
  #define si_swapinfo(val) \
  	do { (val)->freeswap = (val)->totalswap = 0; } while (0)

  /* only sparc can not include linux/pagemap.h in this file
   * so leave page_cache_release and release_pages undeclared... */

  #define free_page_and_swap_cache(page) \
  	page_cache_release(page)
  #define free_pages_and_swap_cache(pages, nr) \
  	release_pages((pages), (nr), 0);

  static inline void show_swap_cache_info(void)
  {
  }

  #define free_swap_and_cache(swp)	is_migration_entry(swp)
  #define swap_duplicate(swp)		is_migration_entry(swp)

  
  static inline void swap_free(swp_entry_t swp)
  {
  }

  static inline struct page *swapin_readahead(swp_entry_t swp, gfp_t gfp_mask,

  			struct vm_area_struct *vma, unsigned long addr)
  {
  	return NULL;
  }
  
  static inline struct page *lookup_swap_cache(swp_entry_t swp)
  {
  	return NULL;
  }

  static inline int add_to_swap(struct page *page)
  {
  	return 0;
  }

  static inline int add_to_swap_cache(struct page *page, swp_entry_t entry,
  							gfp_t gfp_mask)

  {

  	return -1;

  }
  
  static inline void __delete_from_swap_cache(struct page *page)
  {
  }
  
  static inline void delete_from_swap_cache(struct page *page)
  {
  }

  #define reuse_swap_page(page)	(page_mapcount(page) == 1)

  static inline int try_to_free_swap(struct page *page)

  {
  	return 0;
  }

  static inline swp_entry_t get_swap_page(void)
  {
  	swp_entry_t entry;
  	entry.val = 0;
  	return entry;
  }
  
  /* linux/mm/thrash.c */
  #define put_swap_token(x) do { } while(0)
  #define grab_swap_token()  do { } while(0)
  #define has_swap_token(x) 0

  #define disable_swap_token() do { } while(0)

  
  #endif /* CONFIG_SWAP */
  #endif /* __KERNEL__*/
  #endif /* _LINUX_SWAP_H */