linux/fs/ntfs/aops.h
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   1/**
   2 * aops.h - Defines for NTFS kernel address space operations and page cache
   3 *          handling.  Part of the Linux-NTFS project.
   4 *
   5 * Copyright (c) 2001-2004 Anton Altaparmakov
   6 * Copyright (c) 2002 Richard Russon
   7 *
   8 * This program/include file is free software; you can redistribute it and/or
   9 * modify it under the terms of the GNU General Public License as published
  10 * by the Free Software Foundation; either version 2 of the License, or
  11 * (at your option) any later version.
  12 *
  13 * This program/include file is distributed in the hope that it will be
  14 * useful, but WITHOUT ANY WARRANTY; without even the implied warranty
  15 * of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16 * GNU General Public License for more details.
  17 *
  18 * You should have received a copy of the GNU General Public License
  19 * along with this program (in the main directory of the Linux-NTFS
  20 * distribution in the file COPYING); if not, write to the Free Software
  21 * Foundation,Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  22 */
  23
  24#ifndef _LINUX_NTFS_AOPS_H
  25#define _LINUX_NTFS_AOPS_H
  26
  27#include <linux/mm.h>
  28#include <linux/highmem.h>
  29#include <linux/pagemap.h>
  30#include <linux/fs.h>
  31
  32#include "inode.h"
  33
  34/**
  35 * ntfs_unmap_page - release a page that was mapped using ntfs_map_page()
  36 * @page:       the page to release
  37 *
  38 * Unpin, unmap and release a page that was obtained from ntfs_map_page().
  39 */
  40static inline void ntfs_unmap_page(struct page *page)
  41{
  42        kunmap(page);
  43        page_cache_release(page);
  44}
  45
  46/**
  47 * ntfs_map_page - map a page into accessible memory, reading it if necessary
  48 * @mapping:    address space for which to obtain the page
  49 * @index:      index into the page cache for @mapping of the page to map
  50 *
  51 * Read a page from the page cache of the address space @mapping at position
  52 * @index, where @index is in units of PAGE_CACHE_SIZE, and not in bytes.
  53 *
  54 * If the page is not in memory it is loaded from disk first using the readpage
  55 * method defined in the address space operations of @mapping and the page is
  56 * added to the page cache of @mapping in the process.
  57 *
  58 * If the page belongs to an mst protected attribute and it is marked as such
  59 * in its ntfs inode (NInoMstProtected()) the mst fixups are applied but no
  60 * error checking is performed.  This means the caller has to verify whether
  61 * the ntfs record(s) contained in the page are valid or not using one of the
  62 * ntfs_is_XXXX_record{,p}() macros, where XXXX is the record type you are
  63 * expecting to see.  (For details of the macros, see fs/ntfs/layout.h.)
  64 *
  65 * If the page is in high memory it is mapped into memory directly addressible
  66 * by the kernel.
  67 *
  68 * Finally the page count is incremented, thus pinning the page into place.
  69 *
  70 * The above means that page_address(page) can be used on all pages obtained
  71 * with ntfs_map_page() to get the kernel virtual address of the page.
  72 *
  73 * When finished with the page, the caller has to call ntfs_unmap_page() to
  74 * unpin, unmap and release the page.
  75 *
  76 * Note this does not grant exclusive access. If such is desired, the caller
  77 * must provide it independently of the ntfs_{un}map_page() calls by using
  78 * a {rw_}semaphore or other means of serialization. A spin lock cannot be
  79 * used as ntfs_map_page() can block.
  80 *
  81 * The unlocked and uptodate page is returned on success or an encoded error
  82 * on failure. Caller has to test for error using the IS_ERR() macro on the
  83 * return value. If that evaluates to 'true', the negative error code can be
  84 * obtained using PTR_ERR() on the return value of ntfs_map_page().
  85 */
  86static inline struct page *ntfs_map_page(struct address_space *mapping,
  87                unsigned long index)
  88{
  89        struct page *page = read_mapping_page(mapping, index, NULL);
  90
  91        if (!IS_ERR(page)) {
  92                kmap(page);
  93                if (!PageError(page))
  94                        return page;
  95                ntfs_unmap_page(page);
  96                return ERR_PTR(-EIO);
  97        }
  98        return page;
  99}
 100
 101#ifdef NTFS_RW
 102
 103extern void mark_ntfs_record_dirty(struct page *page, const unsigned int ofs);
 104
 105#endif /* NTFS_RW */
 106
 107#endif /* _LINUX_NTFS_AOPS_H */
 108
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