fs/ntfs/aops.h

   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  */
  40 static 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  */
  86 static 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
 103 extern void mark_ntfs_record_dirty(struct page *page, const unsigned int ofs);
 104
 105 #endif /* NTFS_RW */
 106
 107 #endif /* _LINUX_NTFS_AOPS_H */