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
157