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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
8/*
9 * Extra info for subpapge bitmap.
10 *
11 * For subpage we pack all uptodate/error/dirty/writeback/ordered bitmaps into
12 * one larger bitmap.
13 *
14 * This structure records how they are organized in the bitmap:
15 *
16 * /- uptodate_offset /- error_offset /- dirty_offset
17 * | | |
18 * v v v
19 * |u|u|u|u|........|u|u|e|e|.......|e|e| ... |o|o|
20 * |<- bitmap_nr_bits ->|
21 * |<--------------- total_nr_bits ---------------->|
22 */
23struct btrfs_subpage_info {
24 /* Number of bits for each bitmap */
25 unsigned int bitmap_nr_bits;
26
27 /* Total number of bits for the whole bitmap */
28 unsigned int total_nr_bits;
29
30 /*
31 * *_start indicates where the bitmap starts, the length is always
32 * @bitmap_size, which is calculated from PAGE_SIZE / sectorsize.
33 */
34 unsigned int uptodate_offset;
35 unsigned int error_offset;
36 unsigned int dirty_offset;
37 unsigned int writeback_offset;
38 unsigned int ordered_offset;
39 unsigned int checked_offset;
40};
41
42/*
43 * Structure to trace status of each sector inside a page, attached to
44 * page::private for both data and metadata inodes.
45 */
46struct btrfs_subpage {
47 /* Common members for both data and metadata pages */
48 spinlock_t lock;
49 /*
50 * Both data and metadata needs to track how many readers are for the
51 * page.
52 * Data relies on @readers to unlock the page when last reader finished.
53 * While metadata doesn't need page unlock, it needs to prevent
54 * page::private get cleared before the last end_page_read().
55 */
56 atomic_t readers;
57 union {
58 /*
59 * Structures only used by metadata
60 *
61 * @eb_refs should only be operated under private_lock, as it
62 * manages whether the subpage can be detached.
63 */
64 atomic_t eb_refs;
65
66 /* Structures only used by data */
67 atomic_t writers;
68 };
69 unsigned long bitmaps[];
70};
71
72enum btrfs_subpage_type {
73 BTRFS_SUBPAGE_METADATA,
74 BTRFS_SUBPAGE_DATA,
75};
76
77void btrfs_init_subpage_info(struct btrfs_subpage_info *subpage_info, u32 sectorsize);
78int btrfs_attach_subpage(const struct btrfs_fs_info *fs_info,
79 struct page *page, enum btrfs_subpage_type type);
80void btrfs_detach_subpage(const struct btrfs_fs_info *fs_info,
81 struct page *page);
82
83/* Allocate additional data where page represents more than one sector */
84struct btrfs_subpage *btrfs_alloc_subpage(const struct btrfs_fs_info *fs_info,
85 enum btrfs_subpage_type type);
86void btrfs_free_subpage(struct btrfs_subpage *subpage);
87
88void btrfs_page_inc_eb_refs(const struct btrfs_fs_info *fs_info,
89 struct page *page);
90void btrfs_page_dec_eb_refs(const struct btrfs_fs_info *fs_info,
91 struct page *page);
92
93void btrfs_subpage_start_reader(const struct btrfs_fs_info *fs_info,
94 struct page *page, u64 start, u32 len);
95void btrfs_subpage_end_reader(const struct btrfs_fs_info *fs_info,
96 struct page *page, u64 start, u32 len);
97
98void btrfs_subpage_start_writer(const struct btrfs_fs_info *fs_info,
99 struct page *page, u64 start, u32 len);
100bool btrfs_subpage_end_and_test_writer(const struct btrfs_fs_info *fs_info,
101 struct page *page, u64 start, u32 len);
102int btrfs_page_start_writer_lock(const struct btrfs_fs_info *fs_info,
103 struct page *page, u64 start, u32 len);
104void btrfs_page_end_writer_lock(const struct btrfs_fs_info *fs_info,
105 struct page *page, u64 start, u32 len);
106
107/*
108 * Template for subpage related operations.
109 *
110 * btrfs_subpage_*() are for call sites where the page has subpage attached and
111 * the range is ensured to be inside the page.
112 *
113 * btrfs_page_*() are for call sites where the page can either be subpage
114 * specific or regular page. The function will handle both cases.
115 * But the range still needs to be inside the page.
116 *
117 * btrfs_page_clamp_*() are similar to btrfs_page_*(), except the range doesn't
118 * need to be inside the page. Those functions will truncate the range
119 * automatically.
120 */
121#define DECLARE_BTRFS_SUBPAGE_OPS(name) \
122void btrfs_subpage_set_##name(const struct btrfs_fs_info *fs_info, \
123 struct page *page, u64 start, u32 len); \
124void btrfs_subpage_clear_##name(const struct btrfs_fs_info *fs_info, \
125 struct page *page, u64 start, u32 len); \
126bool btrfs_subpage_test_##name(const struct btrfs_fs_info *fs_info, \
127 struct page *page, u64 start, u32 len); \
128void btrfs_page_set_##name(const struct btrfs_fs_info *fs_info, \
129 struct page *page, u64 start, u32 len); \
130void btrfs_page_clear_##name(const struct btrfs_fs_info *fs_info, \
131 struct page *page, u64 start, u32 len); \
132bool btrfs_page_test_##name(const struct btrfs_fs_info *fs_info, \
133 struct page *page, u64 start, u32 len); \
134void btrfs_page_clamp_set_##name(const struct btrfs_fs_info *fs_info, \
135 struct page *page, u64 start, u32 len); \
136void btrfs_page_clamp_clear_##name(const struct btrfs_fs_info *fs_info, \
137 struct page *page, u64 start, u32 len); \
138bool btrfs_page_clamp_test_##name(const struct btrfs_fs_info *fs_info, \
139 struct page *page, u64 start, u32 len);
140
141DECLARE_BTRFS_SUBPAGE_OPS(uptodate);
142DECLARE_BTRFS_SUBPAGE_OPS(error);
143DECLARE_BTRFS_SUBPAGE_OPS(dirty);
144DECLARE_BTRFS_SUBPAGE_OPS(writeback);
145DECLARE_BTRFS_SUBPAGE_OPS(ordered);
146DECLARE_BTRFS_SUBPAGE_OPS(checked);
147
148bool btrfs_subpage_clear_and_test_dirty(const struct btrfs_fs_info *fs_info,
149 struct page *page, u64 start, u32 len);
150
151void btrfs_page_assert_not_dirty(const struct btrfs_fs_info *fs_info,
152 struct page *page);
153void btrfs_page_unlock_writer(struct btrfs_fs_info *fs_info, struct page *page,
154 u64 start, u32 len);
155
156#endif