#ifndef _LINUX_PAGEMAP_H
  #define _LINUX_PAGEMAP_H
  
  /*
   * Copyright 1995 Linus Torvalds
   */
  #include <linux/mm.h>
  #include <linux/fs.h>
  #include <linux/list.h>
  #include <linux/highmem.h>
  #include <linux/compiler.h>
  #include <asm/uaccess.h>
  #include <linux/gfp.h>

  #include <linux/bitops.h>

  
  /*
   * Bits in mapping->flags.  The lower __GFP_BITS_SHIFT bits are the page
   * allocation mode flags.
   */
  #define	AS_EIO		(__GFP_BITS_SHIFT + 0)	/* IO error on async write */
  #define AS_ENOSPC	(__GFP_BITS_SHIFT + 1)	/* ENOSPC on async write */

  static inline void mapping_set_error(struct address_space *mapping, int error)
  {
  	if (error) {
  		if (error == -ENOSPC)
  			set_bit(AS_ENOSPC, &mapping->flags);
  		else
  			set_bit(AS_EIO, &mapping->flags);
  	}
  }

  static inline gfp_t mapping_gfp_mask(struct address_space * mapping)

  {

  	return (__force gfp_t)mapping->flags & __GFP_BITS_MASK;

  }
  
  /*
   * This is non-atomic.  Only to be used before the mapping is activated.
   * Probably needs a barrier...
   */

  static inline void mapping_set_gfp_mask(struct address_space *m, gfp_t mask)

  {

  	m->flags = (m->flags & ~(__force unsigned long)__GFP_BITS_MASK) |
  				(__force unsigned long)mask;

  }
  
  /*
   * The page cache can done in larger chunks than
   * one page, because it allows for more efficient
   * throughput (it can then be mapped into user
   * space in smaller chunks for same flexibility).
   *
   * Or rather, it _will_ be done in larger chunks.
   */
  #define PAGE_CACHE_SHIFT	PAGE_SHIFT
  #define PAGE_CACHE_SIZE		PAGE_SIZE
  #define PAGE_CACHE_MASK		PAGE_MASK
  #define PAGE_CACHE_ALIGN(addr)	(((addr)+PAGE_CACHE_SIZE-1)&PAGE_CACHE_MASK)
  
  #define page_cache_get(page)		get_page(page)
  #define page_cache_release(page)	put_page(page)
  void release_pages(struct page **pages, int nr, int cold);

  #ifdef CONFIG_NUMA

  extern struct page *__page_cache_alloc(gfp_t gfp);

  #else

  static inline struct page *__page_cache_alloc(gfp_t gfp)
  {
  	return alloc_pages(gfp, 0);
  }
  #endif

  static inline struct page *page_cache_alloc(struct address_space *x)
  {

  	return __page_cache_alloc(mapping_gfp_mask(x));

  }
  
  static inline struct page *page_cache_alloc_cold(struct address_space *x)
  {

  	return __page_cache_alloc(mapping_gfp_mask(x)|__GFP_COLD);

  }
  
  typedef int filler_t(void *, struct page *);
  
  extern struct page * find_get_page(struct address_space *mapping,
  				unsigned long index);
  extern struct page * find_lock_page(struct address_space *mapping,
  				unsigned long index);

  extern struct page * find_or_create_page(struct address_space *mapping,

  				unsigned long index, gfp_t gfp_mask);

  unsigned find_get_pages(struct address_space *mapping, pgoff_t start,
  			unsigned int nr_pages, struct page **pages);

  unsigned find_get_pages_contig(struct address_space *mapping, pgoff_t start,
  			       unsigned int nr_pages, struct page **pages);

  unsigned find_get_pages_tag(struct address_space *mapping, pgoff_t *index,
  			int tag, unsigned int nr_pages, struct page **pages);
  
  /*
   * Returns locked page at given index in given cache, creating it if needed.
   */
  static inline struct page *grab_cache_page(struct address_space *mapping, unsigned long index)
  {
  	return find_or_create_page(mapping, index, mapping_gfp_mask(mapping));
  }
  
  extern struct page * grab_cache_page_nowait(struct address_space *mapping,
  				unsigned long index);

  extern struct page * read_cache_page_async(struct address_space *mapping,
  				unsigned long index, filler_t *filler,
  				void *data);

  extern struct page * read_cache_page(struct address_space *mapping,
  				unsigned long index, filler_t *filler,
  				void *data);
  extern int read_cache_pages(struct address_space *mapping,
  		struct list_head *pages, filler_t *filler, void *data);

  static inline struct page *read_mapping_page_async(
  						struct address_space *mapping,
  					     unsigned long index, void *data)
  {
  	filler_t *filler = (filler_t *)mapping->a_ops->readpage;
  	return read_cache_page_async(mapping, index, filler, data);
  }

  static inline struct page *read_mapping_page(struct address_space *mapping,
  					     unsigned long index, void *data)
  {
  	filler_t *filler = (filler_t *)mapping->a_ops->readpage;
  	return read_cache_page(mapping, index, filler, data);
  }

  int add_to_page_cache(struct page *page, struct address_space *mapping,

  				unsigned long index, gfp_t gfp_mask);

  int add_to_page_cache_lru(struct page *page, struct address_space *mapping,

  				unsigned long index, gfp_t gfp_mask);

  extern void remove_from_page_cache(struct page *page);
  extern void __remove_from_page_cache(struct page *page);

  /*
   * Return byte-offset into filesystem object for page.
   */
  static inline loff_t page_offset(struct page *page)
  {
  	return ((loff_t)page->index) << PAGE_CACHE_SHIFT;
  }
  
  static inline pgoff_t linear_page_index(struct vm_area_struct *vma,
  					unsigned long address)
  {
  	pgoff_t pgoff = (address - vma->vm_start) >> PAGE_SHIFT;
  	pgoff += vma->vm_pgoff;
  	return pgoff >> (PAGE_CACHE_SHIFT - PAGE_SHIFT);
  }
  
  extern void FASTCALL(__lock_page(struct page *page));

  extern void FASTCALL(__lock_page_nosync(struct page *page));

  extern void FASTCALL(unlock_page(struct page *page));

  /*
   * lock_page may only be called if we have the page's inode pinned.
   */

  static inline void lock_page(struct page *page)
  {
  	might_sleep();
  	if (TestSetPageLocked(page))
  		__lock_page(page);
  }

  
  /*
   * lock_page_nosync should only be used if we can't pin the page's inode.
   * Doesn't play quite so well with block device plugging.
   */
  static inline void lock_page_nosync(struct page *page)
  {
  	might_sleep();
  	if (TestSetPageLocked(page))
  		__lock_page_nosync(page);
  }

  	
  /*
   * This is exported only for wait_on_page_locked/wait_on_page_writeback.
   * Never use this directly!
   */
  extern void FASTCALL(wait_on_page_bit(struct page *page, int bit_nr));
  
  /* 
   * Wait for a page to be unlocked.
   *
   * This must be called with the caller "holding" the page,
   * ie with increased "page->count" so that the page won't
   * go away during the wait..
   */
  static inline void wait_on_page_locked(struct page *page)
  {
  	if (PageLocked(page))
  		wait_on_page_bit(page, PG_locked);
  }
  
  /* 
   * Wait for a page to complete writeback
   */
  static inline void wait_on_page_writeback(struct page *page)
  {
  	if (PageWriteback(page))
  		wait_on_page_bit(page, PG_writeback);
  }
  
  extern void end_page_writeback(struct page *page);
  
  /*
   * Fault a userspace page into pagetables.  Return non-zero on a fault.
   *
   * This assumes that two userspace pages are always sufficient.  That's
   * not true if PAGE_CACHE_SIZE > PAGE_SIZE.
   */
  static inline int fault_in_pages_writeable(char __user *uaddr, int size)
  {
  	int ret;
  
  	/*
  	 * Writing zeroes into userspace here is OK, because we know that if
  	 * the zero gets there, we'll be overwriting it.
  	 */
  	ret = __put_user(0, uaddr);
  	if (ret == 0) {
  		char __user *end = uaddr + size - 1;
  
  		/*
  		 * If the page was already mapped, this will get a cache miss
  		 * for sure, so try to avoid doing it.
  		 */
  		if (((unsigned long)uaddr & PAGE_MASK) !=
  				((unsigned long)end & PAGE_MASK))
  		 	ret = __put_user(0, end);
  	}
  	return ret;
  }
  
  static inline void fault_in_pages_readable(const char __user *uaddr, int size)
  {
  	volatile char c;
  	int ret;
  
  	ret = __get_user(c, uaddr);
  	if (ret == 0) {
  		const char __user *end = uaddr + size - 1;
  
  		if (((unsigned long)uaddr & PAGE_MASK) !=
  				((unsigned long)end & PAGE_MASK))
  		 	__get_user(c, end);
  	}
  }
  
  #endif /* _LINUX_PAGEMAP_H */