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 */
108
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