#ifndef _LINUX_FRONTSWAP_H
  #define _LINUX_FRONTSWAP_H
  
  #include <linux/swap.h>
  #include <linux/mm.h>
  #include <linux/bitops.h>
  
  struct frontswap_ops {

  	void (*init)(unsigned); /* this swap type was just swapon'ed */
  	int (*store)(unsigned, pgoff_t, struct page *); /* store a page */
  	int (*load)(unsigned, pgoff_t, struct page *); /* load a page */
  	void (*invalidate_page)(unsigned, pgoff_t); /* page no longer needed */
  	void (*invalidate_area)(unsigned); /* swap type just swapoff'ed */
  	struct frontswap_ops *next; /* private pointer to next ops */

  };
  
  extern bool frontswap_enabled;

  extern void frontswap_register_ops(struct frontswap_ops *ops);

  extern void frontswap_shrink(unsigned long);
  extern unsigned long frontswap_curr_pages(void);
  extern void frontswap_writethrough(bool);

  #define FRONTSWAP_HAS_EXCLUSIVE_GETS
  extern void frontswap_tmem_exclusive_gets(bool);

  extern bool __frontswap_test(struct swap_info_struct *, pgoff_t);

  extern void __frontswap_init(unsigned type, unsigned long *map);

  extern int __frontswap_store(struct page *page);
  extern int __frontswap_load(struct page *page);

  extern void __frontswap_invalidate_page(unsigned, pgoff_t);
  extern void __frontswap_invalidate_area(unsigned);
  
  #ifdef CONFIG_FRONTSWAP

  #define frontswap_enabled (1)

  
  static inline bool frontswap_test(struct swap_info_struct *sis, pgoff_t offset)
  {

  	return __frontswap_test(sis, offset);

  }
  
  static inline void frontswap_map_set(struct swap_info_struct *p,
  				     unsigned long *map)
  {
  	p->frontswap_map = map;
  }
  
  static inline unsigned long *frontswap_map_get(struct swap_info_struct *p)
  {
  	return p->frontswap_map;
  }
  #else
  /* all inline routines become no-ops and all externs are ignored */
  
  #define frontswap_enabled (0)
  
  static inline bool frontswap_test(struct swap_info_struct *sis, pgoff_t offset)
  {
  	return false;
  }

  static inline void frontswap_map_set(struct swap_info_struct *p,
  				     unsigned long *map)
  {
  }
  
  static inline unsigned long *frontswap_map_get(struct swap_info_struct *p)
  {
  	return NULL;
  }
  #endif

  static inline int frontswap_store(struct page *page)

  {
  	int ret = -1;
  
  	if (frontswap_enabled)

  		ret = __frontswap_store(page);

  	return ret;
  }

  static inline int frontswap_load(struct page *page)

  {
  	int ret = -1;
  
  	if (frontswap_enabled)

  		ret = __frontswap_load(page);

  	return ret;
  }
  
  static inline void frontswap_invalidate_page(unsigned type, pgoff_t offset)
  {
  	if (frontswap_enabled)
  		__frontswap_invalidate_page(type, offset);
  }
  
  static inline void frontswap_invalidate_area(unsigned type)
  {
  	if (frontswap_enabled)
  		__frontswap_invalidate_area(type);
  }

  static inline void frontswap_init(unsigned type, unsigned long *map)

  {
  	if (frontswap_enabled)

  		__frontswap_init(type, map);

  }
  
  #endif /* _LINUX_FRONTSWAP_H */