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  */
23 struct 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  */
46 struct 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 
72 enum btrfs_subpage_type {
73 	BTRFS_SUBPAGE_METADATA,
74 	BTRFS_SUBPAGE_DATA,
75 };
76 
77 bool btrfs_is_subpage(const struct btrfs_fs_info *fs_info, struct page *page);
78 
79 void btrfs_init_subpage_info(struct btrfs_subpage_info *subpage_info, u32 sectorsize);
80 int btrfs_attach_subpage(const struct btrfs_fs_info *fs_info,
81 			 struct page *page, enum btrfs_subpage_type type);
82 void btrfs_detach_subpage(const struct btrfs_fs_info *fs_info,
83 			  struct page *page);
84 
85 /* Allocate additional data where page represents more than one sector */
86 struct btrfs_subpage *btrfs_alloc_subpage(const struct btrfs_fs_info *fs_info,
87 					  enum btrfs_subpage_type type);
88 void btrfs_free_subpage(struct btrfs_subpage *subpage);
89 
90 void btrfs_page_inc_eb_refs(const struct btrfs_fs_info *fs_info,
91 			    struct page *page);
92 void btrfs_page_dec_eb_refs(const struct btrfs_fs_info *fs_info,
93 			    struct page *page);
94 
95 void btrfs_subpage_start_reader(const struct btrfs_fs_info *fs_info,
96 		struct page *page, u64 start, u32 len);
97 void btrfs_subpage_end_reader(const struct btrfs_fs_info *fs_info,
98 		struct page *page, u64 start, u32 len);
99 
100 void btrfs_subpage_start_writer(const struct btrfs_fs_info *fs_info,
101 		struct page *page, u64 start, u32 len);
102 bool btrfs_subpage_end_and_test_writer(const struct btrfs_fs_info *fs_info,
103 		struct page *page, u64 start, u32 len);
104 int btrfs_page_start_writer_lock(const struct btrfs_fs_info *fs_info,
105 		struct page *page, u64 start, u32 len);
106 void btrfs_page_end_writer_lock(const struct btrfs_fs_info *fs_info,
107 		struct page *page, u64 start, u32 len);
108 
109 /*
110  * Template for subpage related operations.
111  *
112  * btrfs_subpage_*() are for call sites where the page has subpage attached and
113  * the range is ensured to be inside the page.
114  *
115  * btrfs_page_*() are for call sites where the page can either be subpage
116  * specific or regular page. The function will handle both cases.
117  * But the range still needs to be inside the page.
118  *
119  * btrfs_page_clamp_*() are similar to btrfs_page_*(), except the range doesn't
120  * need to be inside the page. Those functions will truncate the range
121  * automatically.
122  */
123 #define DECLARE_BTRFS_SUBPAGE_OPS(name)					\
124 void btrfs_subpage_set_##name(const struct btrfs_fs_info *fs_info,	\
125 		struct page *page, u64 start, u32 len);			\
126 void btrfs_subpage_clear_##name(const struct btrfs_fs_info *fs_info,	\
127 		struct page *page, u64 start, u32 len);			\
128 bool btrfs_subpage_test_##name(const struct btrfs_fs_info *fs_info,	\
129 		struct page *page, u64 start, u32 len);			\
130 void btrfs_page_set_##name(const struct btrfs_fs_info *fs_info,		\
131 		struct page *page, u64 start, u32 len);			\
132 void btrfs_page_clear_##name(const struct btrfs_fs_info *fs_info,	\
133 		struct page *page, u64 start, u32 len);			\
134 bool btrfs_page_test_##name(const struct btrfs_fs_info *fs_info,	\
135 		struct page *page, u64 start, u32 len);			\
136 void btrfs_page_clamp_set_##name(const struct btrfs_fs_info *fs_info,	\
137 		struct page *page, u64 start, u32 len);			\
138 void btrfs_page_clamp_clear_##name(const struct btrfs_fs_info *fs_info,	\
139 		struct page *page, u64 start, u32 len);			\
140 bool btrfs_page_clamp_test_##name(const struct btrfs_fs_info *fs_info,	\
141 		struct page *page, u64 start, u32 len);
142 
143 DECLARE_BTRFS_SUBPAGE_OPS(uptodate);
144 DECLARE_BTRFS_SUBPAGE_OPS(error);
145 DECLARE_BTRFS_SUBPAGE_OPS(dirty);
146 DECLARE_BTRFS_SUBPAGE_OPS(writeback);
147 DECLARE_BTRFS_SUBPAGE_OPS(ordered);
148 DECLARE_BTRFS_SUBPAGE_OPS(checked);
149 
150 bool btrfs_subpage_clear_and_test_dirty(const struct btrfs_fs_info *fs_info,
151 		struct page *page, u64 start, u32 len);
152 
153 void btrfs_page_assert_not_dirty(const struct btrfs_fs_info *fs_info,
154 				 struct page *page);
155 void btrfs_page_unlock_writer(struct btrfs_fs_info *fs_info, struct page *page,
156 			      u64 start, u32 len);
157 
158 #endif
159