/**
   * aops.h - Defines for NTFS kernel address space operations and page cache
   *	    handling.  Part of the Linux-NTFS project.
   *
   * Copyright (c) 2001-2004 Anton Altaparmakov
   * Copyright (c) 2002 Richard Russon
   *
   * This program/include file is free software; you can redistribute it and/or
   * modify it under the terms of the GNU General Public License as published
   * by the Free Software Foundation; either version 2 of the License, or
   * (at your option) any later version.
   *
   * This program/include file is distributed in the hope that it will be
   * useful, but WITHOUT ANY WARRANTY; without even the implied warranty
   * of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   * GNU General Public License for more details.
   *
   * You should have received a copy of the GNU General Public License
   * along with this program (in the main directory of the Linux-NTFS
   * distribution in the file COPYING); if not, write to the Free Software
   * Foundation,Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
   */
  
  #ifndef _LINUX_NTFS_AOPS_H
  #define _LINUX_NTFS_AOPS_H
  
  #include <linux/mm.h>
  #include <linux/highmem.h>
  #include <linux/pagemap.h>
  #include <linux/fs.h>
  
  #include "inode.h"
  
  /**
   * ntfs_unmap_page - release a page that was mapped using ntfs_map_page()
   * @page:	the page to release
   *
   * Unpin, unmap and release a page that was obtained from ntfs_map_page().
   */
  static inline void ntfs_unmap_page(struct page *page)
  {
  	kunmap(page);
  	page_cache_release(page);
  }
  
  /**
   * ntfs_map_page - map a page into accessible memory, reading it if necessary
   * @mapping:	address space for which to obtain the page
   * @index:	index into the page cache for @mapping of the page to map
   *
   * Read a page from the page cache of the address space @mapping at position
   * @index, where @index is in units of PAGE_CACHE_SIZE, and not in bytes.
   *
   * If the page is not in memory it is loaded from disk first using the readpage
   * method defined in the address space operations of @mapping and the page is
   * added to the page cache of @mapping in the process.
   *
   * If the page belongs to an mst protected attribute and it is marked as such
   * in its ntfs inode (NInoMstProtected()) the mst fixups are applied but no
   * error checking is performed.  This means the caller has to verify whether
   * the ntfs record(s) contained in the page are valid or not using one of the
   * ntfs_is_XXXX_record{,p}() macros, where XXXX is the record type you are
   * expecting to see.  (For details of the macros, see fs/ntfs/layout.h.)
   *
   * If the page is in high memory it is mapped into memory directly addressible
   * by the kernel.
   *
   * Finally the page count is incremented, thus pinning the page into place.
   *
   * The above means that page_address(page) can be used on all pages obtained
   * with ntfs_map_page() to get the kernel virtual address of the page.
   *
   * When finished with the page, the caller has to call ntfs_unmap_page() to
   * unpin, unmap and release the page.
   *
   * Note this does not grant exclusive access. If such is desired, the caller
   * must provide it independently of the ntfs_{un}map_page() calls by using
   * a {rw_}semaphore or other means of serialization. A spin lock cannot be
   * used as ntfs_map_page() can block.
   *
   * The unlocked and uptodate page is returned on success or an encoded error
   * on failure. Caller has to test for error using the IS_ERR() macro on the

   * return value. If that evaluates to 'true', the negative error code can be

   * obtained using PTR_ERR() on the return value of ntfs_map_page().
   */
  static inline struct page *ntfs_map_page(struct address_space *mapping,
  		unsigned long index)
  {

  	struct page *page = read_mapping_page(mapping, index, NULL);

  
  	if (!IS_ERR(page)) {

  		kmap(page);

  		if (!PageError(page))

  			return page;
  		ntfs_unmap_page(page);
  		return ERR_PTR(-EIO);
  	}
  	return page;
  }
  
  #ifdef NTFS_RW
  
  extern void mark_ntfs_record_dirty(struct page *page, const unsigned int ofs);
  
  #endif /* NTFS_RW */
  
  #endif /* _LINUX_NTFS_AOPS_H */