1 /* SPDX-License-Identifier: GPL-2.0 */
2
3 #ifndef BTRFS_SUBPAGE_H
4 #define BTRFS_SUBPAGE_H
5
6 #include <linux/spinlock.h>
7 #include <linux/atomic.h>
8
9 struct address_space;
10 struct folio;
11 struct btrfs_fs_info;
12
13 /*
14 * Extra info for subpapge bitmap.
15 *
16 * For subpage we pack all uptodate/dirty/writeback/ordered bitmaps into
17 * one larger bitmap.
18 *
19 * This structure records how they are organized in the bitmap:
20 *
21 * /- uptodate_offset /- dirty_offset /- ordered_offset
22 * | | |
23 * v v v
24 * |u|u|u|u|........|u|u|d|d|.......|d|d|o|o|.......|o|o|
25 * |<- bitmap_nr_bits ->|
26 * |<----------------- total_nr_bits ------------------>|
27 */
28 struct btrfs_subpage_info {
29 /* Number of bits for each bitmap */
30 unsigned int bitmap_nr_bits;
31
32 /* Total number of bits for the whole bitmap */
33 unsigned int total_nr_bits;
34
35 /*
36 * *_offset indicates where the bitmap starts, the length is always
37 * @bitmap_size, which is calculated from PAGE_SIZE / sectorsize.
38 */
39 unsigned int uptodate_offset;
40 unsigned int dirty_offset;
41 unsigned int writeback_offset;
42 unsigned int ordered_offset;
43 unsigned int checked_offset;
44
45 /*
46 * For locked bitmaps, normally it's subpage representation for folio
47 * Locked flag, but metadata is different:
48 *
49 * - Metadata doesn't really lock the folio
50 * It's just to prevent page::private get cleared before the last
51 * end_page_read().
52 */
53 unsigned int locked_offset;
54 };
55
56 /*
57 * Structure to trace status of each sector inside a page, attached to
58 * page::private for both data and metadata inodes.
59 */
60 struct btrfs_subpage {
61 /* Common members for both data and metadata pages */
62 spinlock_t lock;
63 /*
64 * Both data and metadata needs to track how many readers are for the
65 * page.
66 * Data relies on @readers to unlock the page when last reader finished.
67 * While metadata doesn't need page unlock, it needs to prevent
68 * page::private get cleared before the last end_page_read().
69 */
70 atomic_t readers;
71 union {
72 /*
73 * Structures only used by metadata
74 *
75 * @eb_refs should only be operated under private_lock, as it
76 * manages whether the subpage can be detached.
77 */
78 atomic_t eb_refs;
79
80 /* Structures only used by data */
81 atomic_t writers;
82 };
83 unsigned long bitmaps[];
84 };
85
86 enum btrfs_subpage_type {
87 BTRFS_SUBPAGE_METADATA,
88 BTRFS_SUBPAGE_DATA,
89 };
90
91 bool btrfs_is_subpage(const struct btrfs_fs_info *fs_info, struct address_space *mapping);
92
93 void btrfs_init_subpage_info(struct btrfs_subpage_info *subpage_info, u32 sectorsize);
94 int btrfs_attach_subpage(const struct btrfs_fs_info *fs_info,
95 struct folio *folio, enum btrfs_subpage_type type);
96 void btrfs_detach_subpage(const struct btrfs_fs_info *fs_info, struct folio *folio);
97
98 /* Allocate additional data where page represents more than one sector */
99 struct btrfs_subpage *btrfs_alloc_subpage(const struct btrfs_fs_info *fs_info,
100 enum btrfs_subpage_type type);
101 void btrfs_free_subpage(struct btrfs_subpage *subpage);
102
103 void btrfs_folio_inc_eb_refs(const struct btrfs_fs_info *fs_info, struct folio *folio);
104 void btrfs_folio_dec_eb_refs(const struct btrfs_fs_info *fs_info, struct folio *folio);
105
106 void btrfs_subpage_start_reader(const struct btrfs_fs_info *fs_info,
107 struct folio *folio, u64 start, u32 len);
108 void btrfs_subpage_end_reader(const struct btrfs_fs_info *fs_info,
109 struct folio *folio, u64 start, u32 len);
110
111 int btrfs_folio_start_writer_lock(const struct btrfs_fs_info *fs_info,
112 struct folio *folio, u64 start, u32 len);
113 void btrfs_folio_end_writer_lock(const struct btrfs_fs_info *fs_info,
114 struct folio *folio, u64 start, u32 len);
115 void btrfs_folio_set_writer_lock(const struct btrfs_fs_info *fs_info,
116 struct folio *folio, u64 start, u32 len);
117 bool btrfs_subpage_find_writer_locked(const struct btrfs_fs_info *fs_info,
118 struct folio *folio, u64 search_start,
119 u64 *found_start_ret, u32 *found_len_ret);
120 void btrfs_folio_end_all_writers(const struct btrfs_fs_info *fs_info, struct folio *folio);
121
122 /*
123 * Template for subpage related operations.
124 *
125 * btrfs_subpage_*() are for call sites where the folio has subpage attached and
126 * the range is ensured to be inside the folio's single page.
127 *
128 * btrfs_folio_*() are for call sites where the page can either be subpage
129 * specific or regular folios. The function will handle both cases.
130 * But the range still needs to be inside one single page.
131 *
132 * btrfs_folio_clamp_*() are similar to btrfs_folio_*(), except the range doesn't
133 * need to be inside the page. Those functions will truncate the range
134 * automatically.
135 */
136 #define DECLARE_BTRFS_SUBPAGE_OPS(name) \
137 void btrfs_subpage_set_##name(const struct btrfs_fs_info *fs_info, \
138 struct folio *folio, u64 start, u32 len); \
139 void btrfs_subpage_clear_##name(const struct btrfs_fs_info *fs_info, \
140 struct folio *folio, u64 start, u32 len); \
141 bool btrfs_subpage_test_##name(const struct btrfs_fs_info *fs_info, \
142 struct folio *folio, u64 start, u32 len); \
143 void btrfs_folio_set_##name(const struct btrfs_fs_info *fs_info, \
144 struct folio *folio, u64 start, u32 len); \
145 void btrfs_folio_clear_##name(const struct btrfs_fs_info *fs_info, \
146 struct folio *folio, u64 start, u32 len); \
147 bool btrfs_folio_test_##name(const struct btrfs_fs_info *fs_info, \
148 struct folio *folio, u64 start, u32 len); \
149 void btrfs_folio_clamp_set_##name(const struct btrfs_fs_info *fs_info, \
150 struct folio *folio, u64 start, u32 len); \
151 void btrfs_folio_clamp_clear_##name(const struct btrfs_fs_info *fs_info, \
152 struct folio *folio, u64 start, u32 len); \
153 bool btrfs_folio_clamp_test_##name(const struct btrfs_fs_info *fs_info, \
154 struct folio *folio, u64 start, u32 len);
155
156 DECLARE_BTRFS_SUBPAGE_OPS(uptodate);
157 DECLARE_BTRFS_SUBPAGE_OPS(dirty);
158 DECLARE_BTRFS_SUBPAGE_OPS(writeback);
159 DECLARE_BTRFS_SUBPAGE_OPS(ordered);
160 DECLARE_BTRFS_SUBPAGE_OPS(checked);
161
162 bool btrfs_subpage_clear_and_test_dirty(const struct btrfs_fs_info *fs_info,
163 struct folio *folio, u64 start, u32 len);
164
165 void btrfs_folio_assert_not_dirty(const struct btrfs_fs_info *fs_info,
166 struct folio *folio, u64 start, u32 len);
167 void btrfs_folio_unlock_writer(struct btrfs_fs_info *fs_info,
168 struct folio *folio, u64 start, u32 len);
169 void __cold btrfs_subpage_dump_bitmap(const struct btrfs_fs_info *fs_info,
170 struct folio *folio, u64 start, u32 len);
171
172 #endif
173
Linux® is a registered trademark of Linus Torvalds in the United States and other countries.
TOMOYO® is a registered trademark of NTT DATA CORPORATION.