#ifndef _LINUX_CLEANCACHE_H
  #define _LINUX_CLEANCACHE_H
  
  #include <linux/fs.h>
  #include <linux/exportfs.h>
  #include <linux/mm.h>

  #define CLEANCACHE_NO_POOL		-1
  #define CLEANCACHE_NO_BACKEND		-2
  #define CLEANCACHE_NO_BACKEND_SHARED	-3

  #define CLEANCACHE_KEY_MAX 6
  
  /*
   * cleancache requires every file with a page in cleancache to have a
   * unique key unless/until the file is removed/truncated.  For some
   * filesystems, the inode number is unique, but for "modern" filesystems
   * an exportable filehandle is required (see exportfs.h)
   */
  struct cleancache_filekey {
  	union {
  		ino_t ino;
  		__u32 fh[CLEANCACHE_KEY_MAX];
  		u32 key[CLEANCACHE_KEY_MAX];
  	} u;
  };
  
  struct cleancache_ops {
  	int (*init_fs)(size_t);
  	int (*init_shared_fs)(char *uuid, size_t);
  	int (*get_page)(int, struct cleancache_filekey,
  			pgoff_t, struct page *);
  	void (*put_page)(int, struct cleancache_filekey,
  			pgoff_t, struct page *);

  	void (*invalidate_page)(int, struct cleancache_filekey, pgoff_t);
  	void (*invalidate_inode)(int, struct cleancache_filekey);
  	void (*invalidate_fs)(int);

  };

  extern int cleancache_register_ops(struct cleancache_ops *ops);

  extern void __cleancache_init_fs(struct super_block *);

  extern void __cleancache_init_shared_fs(struct super_block *);

  extern int  __cleancache_get_page(struct page *);
  extern void __cleancache_put_page(struct page *);

  extern void __cleancache_invalidate_page(struct address_space *, struct page *);
  extern void __cleancache_invalidate_inode(struct address_space *);
  extern void __cleancache_invalidate_fs(struct super_block *);

  
  #ifdef CONFIG_CLEANCACHE

  #define cleancache_enabled (1)

  static inline bool cleancache_fs_enabled(struct page *page)
  {
  	return page->mapping->host->i_sb->cleancache_poolid >= 0;
  }
  static inline bool cleancache_fs_enabled_mapping(struct address_space *mapping)
  {
  	return mapping->host->i_sb->cleancache_poolid >= 0;
  }
  #else
  #define cleancache_enabled (0)
  #define cleancache_fs_enabled(_page) (0)
  #define cleancache_fs_enabled_mapping(_page) (0)
  #endif
  
  /*
   * The shim layer provided by these inline functions allows the compiler
   * to reduce all cleancache hooks to nothingness if CONFIG_CLEANCACHE
   * is disabled, to a single global variable check if CONFIG_CLEANCACHE
   * is enabled but no cleancache "backend" has dynamically enabled it,
   * and, for the most frequent cleancache ops, to a single global variable
   * check plus a superblock element comparison if CONFIG_CLEANCACHE is enabled
   * and a cleancache backend has dynamically enabled cleancache, but the
   * filesystem referenced by that cleancache op has not enabled cleancache.
   * As a result, CONFIG_CLEANCACHE can be enabled by default with essentially
   * no measurable performance impact.
   */
  
  static inline void cleancache_init_fs(struct super_block *sb)
  {
  	if (cleancache_enabled)
  		__cleancache_init_fs(sb);
  }

  static inline void cleancache_init_shared_fs(struct super_block *sb)

  {
  	if (cleancache_enabled)

  		__cleancache_init_shared_fs(sb);

  }
  
  static inline int cleancache_get_page(struct page *page)
  {
  	int ret = -1;
  
  	if (cleancache_enabled && cleancache_fs_enabled(page))
  		ret = __cleancache_get_page(page);
  	return ret;
  }
  
  static inline void cleancache_put_page(struct page *page)
  {
  	if (cleancache_enabled && cleancache_fs_enabled(page))
  		__cleancache_put_page(page);
  }

  static inline void cleancache_invalidate_page(struct address_space *mapping,

  					struct page *page)
  {
  	/* careful... page->mapping is NULL sometimes when this is called */
  	if (cleancache_enabled && cleancache_fs_enabled_mapping(mapping))

  		__cleancache_invalidate_page(mapping, page);

  }

  static inline void cleancache_invalidate_inode(struct address_space *mapping)

  {
  	if (cleancache_enabled && cleancache_fs_enabled_mapping(mapping))

  		__cleancache_invalidate_inode(mapping);

  }

  static inline void cleancache_invalidate_fs(struct super_block *sb)

  {
  	if (cleancache_enabled)

  		__cleancache_invalidate_fs(sb);

  }
  
  #endif /* _LINUX_CLEANCACHE_H */