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
9struct address_space;
10struct folio;
11struct 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 */
28struct 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 */
60struct 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
86enum btrfs_subpage_type {
87	BTRFS_SUBPAGE_METADATA,
88	BTRFS_SUBPAGE_DATA,
89};
90
91bool btrfs_is_subpage(const struct btrfs_fs_info *fs_info, struct address_space *mapping);
92
93void btrfs_init_subpage_info(struct btrfs_subpage_info *subpage_info, u32 sectorsize);
94int btrfs_attach_subpage(const struct btrfs_fs_info *fs_info,
95			 struct folio *folio, enum btrfs_subpage_type type);
96void 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 */
99struct btrfs_subpage *btrfs_alloc_subpage(const struct btrfs_fs_info *fs_info,
100					  enum btrfs_subpage_type type);
101void btrfs_free_subpage(struct btrfs_subpage *subpage);
102
103void btrfs_folio_inc_eb_refs(const struct btrfs_fs_info *fs_info, struct folio *folio);
104void btrfs_folio_dec_eb_refs(const struct btrfs_fs_info *fs_info, struct folio *folio);
105
106void btrfs_subpage_start_reader(const struct btrfs_fs_info *fs_info,
107				struct folio *folio, u64 start, u32 len);
108void btrfs_subpage_end_reader(const struct btrfs_fs_info *fs_info,
109			      struct folio *folio, u64 start, u32 len);
110
111int btrfs_folio_start_writer_lock(const struct btrfs_fs_info *fs_info,
112				  struct folio *folio, u64 start, u32 len);
113void btrfs_folio_end_writer_lock(const struct btrfs_fs_info *fs_info,
114				 struct folio *folio, u64 start, u32 len);
115
116/*
117 * Template for subpage related operations.
118 *
119 * btrfs_subpage_*() are for call sites where the folio has subpage attached and
120 * the range is ensured to be inside the folio's single page.
121 *
122 * btrfs_folio_*() are for call sites where the page can either be subpage
123 * specific or regular folios. The function will handle both cases.
124 * But the range still needs to be inside one single page.
125 *
126 * btrfs_folio_clamp_*() are similar to btrfs_folio_*(), except the range doesn't
127 * need to be inside the page. Those functions will truncate the range
128 * automatically.
129 */
130#define DECLARE_BTRFS_SUBPAGE_OPS(name)					\
131void btrfs_subpage_set_##name(const struct btrfs_fs_info *fs_info,	\
132		struct folio *folio, u64 start, u32 len);			\
133void btrfs_subpage_clear_##name(const struct btrfs_fs_info *fs_info,	\
134		struct folio *folio, u64 start, u32 len);			\
135bool btrfs_subpage_test_##name(const struct btrfs_fs_info *fs_info,	\
136		struct folio *folio, u64 start, u32 len);			\
137void btrfs_folio_set_##name(const struct btrfs_fs_info *fs_info,	\
138		struct folio *folio, u64 start, u32 len);			\
139void btrfs_folio_clear_##name(const struct btrfs_fs_info *fs_info,	\
140		struct folio *folio, u64 start, u32 len);			\
141bool btrfs_folio_test_##name(const struct btrfs_fs_info *fs_info,	\
142		struct folio *folio, u64 start, u32 len);			\
143void btrfs_folio_clamp_set_##name(const struct btrfs_fs_info *fs_info,	\
144		struct folio *folio, u64 start, u32 len);			\
145void btrfs_folio_clamp_clear_##name(const struct btrfs_fs_info *fs_info,	\
146		struct folio *folio, u64 start, u32 len);			\
147bool btrfs_folio_clamp_test_##name(const struct btrfs_fs_info *fs_info,	\
148		struct folio *folio, u64 start, u32 len);
149
150DECLARE_BTRFS_SUBPAGE_OPS(uptodate);
151DECLARE_BTRFS_SUBPAGE_OPS(dirty);
152DECLARE_BTRFS_SUBPAGE_OPS(writeback);
153DECLARE_BTRFS_SUBPAGE_OPS(ordered);
154DECLARE_BTRFS_SUBPAGE_OPS(checked);
155
156bool btrfs_subpage_clear_and_test_dirty(const struct btrfs_fs_info *fs_info,
157					struct folio *folio, u64 start, u32 len);
158
159void btrfs_folio_assert_not_dirty(const struct btrfs_fs_info *fs_info, struct folio *folio);
160void btrfs_folio_unlock_writer(struct btrfs_fs_info *fs_info,
161			       struct folio *folio, u64 start, u32 len);
162void __cold btrfs_subpage_dump_bitmap(const struct btrfs_fs_info *fs_info,
163				      struct folio *folio, u64 start, u32 len);
164
165#endif
166