1 | /* SPDX-License-Identifier: GPL-2.0-or-later */ |
2 | /* |
3 | * aops.h - Defines for NTFS kernel address space operations and page cache |
4 | * handling. Part of the Linux-NTFS project. |
5 | * |
6 | * Copyright (c) 2001-2004 Anton Altaparmakov |
7 | * Copyright (c) 2002 Richard Russon |
8 | */ |
9 | |
10 | #ifndef _LINUX_NTFS_AOPS_H |
11 | #define _LINUX_NTFS_AOPS_H |
12 | |
13 | #include <linux/mm.h> |
14 | #include <linux/highmem.h> |
15 | #include <linux/pagemap.h> |
16 | #include <linux/fs.h> |
17 | |
18 | #include "inode.h" |
19 | |
20 | /** |
21 | * ntfs_unmap_page - release a page that was mapped using ntfs_map_page() |
22 | * @page: the page to release |
23 | * |
24 | * Unpin, unmap and release a page that was obtained from ntfs_map_page(). |
25 | */ |
26 | static inline void ntfs_unmap_page(struct page *page) |
27 | { |
28 | kunmap(page); |
29 | put_page(page); |
30 | } |
31 | |
32 | /** |
33 | * ntfs_map_page - map a page into accessible memory, reading it if necessary |
34 | * @mapping: address space for which to obtain the page |
35 | * @index: index into the page cache for @mapping of the page to map |
36 | * |
37 | * Read a page from the page cache of the address space @mapping at position |
38 | * @index, where @index is in units of PAGE_SIZE, and not in bytes. |
39 | * |
40 | * If the page is not in memory it is loaded from disk first using the |
41 | * read_folio method defined in the address space operations of @mapping |
42 | * and the page is added to the page cache of @mapping in the process. |
43 | * |
44 | * If the page belongs to an mst protected attribute and it is marked as such |
45 | * in its ntfs inode (NInoMstProtected()) the mst fixups are applied but no |
46 | * error checking is performed. This means the caller has to verify whether |
47 | * the ntfs record(s) contained in the page are valid or not using one of the |
48 | * ntfs_is_XXXX_record{,p}() macros, where XXXX is the record type you are |
49 | * expecting to see. (For details of the macros, see fs/ntfs/layout.h.) |
50 | * |
51 | * If the page is in high memory it is mapped into memory directly addressible |
52 | * by the kernel. |
53 | * |
54 | * Finally the page count is incremented, thus pinning the page into place. |
55 | * |
56 | * The above means that page_address(page) can be used on all pages obtained |
57 | * with ntfs_map_page() to get the kernel virtual address of the page. |
58 | * |
59 | * When finished with the page, the caller has to call ntfs_unmap_page() to |
60 | * unpin, unmap and release the page. |
61 | * |
62 | * Note this does not grant exclusive access. If such is desired, the caller |
63 | * must provide it independently of the ntfs_{un}map_page() calls by using |
64 | * a {rw_}semaphore or other means of serialization. A spin lock cannot be |
65 | * used as ntfs_map_page() can block. |
66 | * |
67 | * The unlocked and uptodate page is returned on success or an encoded error |
68 | * on failure. Caller has to test for error using the IS_ERR() macro on the |
69 | * return value. If that evaluates to 'true', the negative error code can be |
70 | * obtained using PTR_ERR() on the return value of ntfs_map_page(). |
71 | */ |
72 | static inline struct page *ntfs_map_page(struct address_space *mapping, |
73 | unsigned long index) |
74 | { |
75 | struct page *page = read_mapping_page(mapping, index, NULL); |
76 | |
77 | if (!IS_ERR(ptr: page)) |
78 | kmap(page); |
79 | return page; |
80 | } |
81 | |
82 | #ifdef NTFS_RW |
83 | |
84 | extern void mark_ntfs_record_dirty(struct page *page, const unsigned int ofs); |
85 | |
86 | #endif /* NTFS_RW */ |
87 | |
88 | #endif /* _LINUX_NTFS_AOPS_H */ |
89 | |