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 */