#ifndef _LINUX_MIGRATE_H
  #define _LINUX_MIGRATE_H

  #include <linux/mm.h>

  #include <linux/mempolicy.h>

  typedef struct page *new_page_t(struct page *, unsigned long private, int **);

  /*
   * MIGRATE_ASYNC means never block
   * MIGRATE_SYNC_LIGHT in the current implementation means to allow blocking
   *	on most operations but not ->writepage as the potential stall time
   *	is too significant
   * MIGRATE_SYNC will block when migrating pages
   */
  enum migrate_mode {
  	MIGRATE_ASYNC,
  	MIGRATE_SYNC_LIGHT,
  	MIGRATE_SYNC,
  };

  #ifdef CONFIG_MIGRATION

  #define PAGE_MIGRATION 1

  extern void putback_lru_pages(struct list_head *l);

  extern int migrate_page(struct address_space *,

  			struct page *, struct page *, enum migrate_mode);

  extern int migrate_pages(struct list_head *l, new_page_t x,

  			unsigned long private, bool offlining,

  			enum migrate_mode mode);

  extern int migrate_huge_pages(struct list_head *l, new_page_t x,

  			unsigned long private, bool offlining,

  			enum migrate_mode mode);

  extern int fail_migrate_page(struct address_space *,
  			struct page *, struct page *);

  
  extern int migrate_prep(void);

  extern int migrate_prep_local(void);

  extern int migrate_vmas(struct mm_struct *mm,
  		const nodemask_t *from, const nodemask_t *to,
  		unsigned long flags);

  extern void migrate_page_copy(struct page *newpage, struct page *page);
  extern int migrate_huge_page_move_mapping(struct address_space *mapping,
  				  struct page *newpage, struct page *page);

  #else

  #define PAGE_MIGRATION 0

  static inline void putback_lru_pages(struct list_head *l) {}

  static inline int migrate_pages(struct list_head *l, new_page_t x,

  		unsigned long private, bool offlining,

  		enum migrate_mode mode) { return -ENOSYS; }

  static inline int migrate_huge_pages(struct list_head *l, new_page_t x,

  		unsigned long private, bool offlining,

  		enum migrate_mode mode) { return -ENOSYS; }

  static inline int migrate_prep(void) { return -ENOSYS; }

  static inline int migrate_prep_local(void) { return -ENOSYS; }

  static inline int migrate_vmas(struct mm_struct *mm,
  		const nodemask_t *from, const nodemask_t *to,
  		unsigned long flags)
  {
  	return -ENOSYS;
  }

  static inline void migrate_page_copy(struct page *newpage,
  				     struct page *page) {}

  static inline int migrate_huge_page_move_mapping(struct address_space *mapping,

  				  struct page *newpage, struct page *page)
  {
  	return -ENOSYS;
  }

  /* Possible settings for the migrate_page() method in address_operations */
  #define migrate_page NULL
  #define fail_migrate_page NULL
  
  #endif /* CONFIG_MIGRATION */
  #endif /* _LINUX_MIGRATE_H */