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  */
ntfs_unmap_page(struct page * page)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  */
ntfs_map_page(struct address_space * mapping,unsigned long index)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