subpage.h revision cc1d0d93
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 * Maximum page size we support is 64K, minimum sector size is 4K, u16 bitmap
10 * is sufficient. Regular bitmap_* is not used due to size reasons.
11 */
12#define BTRFS_SUBPAGE_BITMAP_SIZE	16
13
14/*
15 * Structure to trace status of each sector inside a page, attached to
16 * page::private for both data and metadata inodes.
17 */
18struct btrfs_subpage {
19	/* Common members for both data and metadata pages */
20	spinlock_t lock;
21	u16 uptodate_bitmap;
22	u16 error_bitmap;
23	u16 dirty_bitmap;
24	u16 writeback_bitmap;
25	/*
26	 * Both data and metadata needs to track how many readers are for the
27	 * page.
28	 * Data relies on @readers to unlock the page when last reader finished.
29	 * While metadata doesn't need page unlock, it needs to prevent
30	 * page::private get cleared before the last end_page_read().
31	 */
32	atomic_t readers;
33	union {
34		/*
35		 * Structures only used by metadata
36		 *
37		 * @eb_refs should only be operated under private_lock, as it
38		 * manages whether the subpage can be detached.
39		 */
40		atomic_t eb_refs;
41		/* Structures only used by data */
42		struct {
43			atomic_t writers;
44
45			/* Tracke pending ordered extent in this sector */
46			u16 ordered_bitmap;
47		};
48	};
49};
50
51enum btrfs_subpage_type {
52	BTRFS_SUBPAGE_METADATA,
53	BTRFS_SUBPAGE_DATA,
54};
55
56int btrfs_attach_subpage(const struct btrfs_fs_info *fs_info,
57			 struct page *page, enum btrfs_subpage_type type);
58void btrfs_detach_subpage(const struct btrfs_fs_info *fs_info,
59			  struct page *page);
60
61/* Allocate additional data where page represents more than one sector */
62int btrfs_alloc_subpage(const struct btrfs_fs_info *fs_info,
63			struct btrfs_subpage **ret,
64			enum btrfs_subpage_type type);
65void btrfs_free_subpage(struct btrfs_subpage *subpage);
66
67void btrfs_page_inc_eb_refs(const struct btrfs_fs_info *fs_info,
68			    struct page *page);
69void btrfs_page_dec_eb_refs(const struct btrfs_fs_info *fs_info,
70			    struct page *page);
71
72void btrfs_subpage_start_reader(const struct btrfs_fs_info *fs_info,
73		struct page *page, u64 start, u32 len);
74void btrfs_subpage_end_reader(const struct btrfs_fs_info *fs_info,
75		struct page *page, u64 start, u32 len);
76
77void btrfs_subpage_start_writer(const struct btrfs_fs_info *fs_info,
78		struct page *page, u64 start, u32 len);
79bool btrfs_subpage_end_and_test_writer(const struct btrfs_fs_info *fs_info,
80		struct page *page, u64 start, u32 len);
81int btrfs_page_start_writer_lock(const struct btrfs_fs_info *fs_info,
82		struct page *page, u64 start, u32 len);
83void btrfs_page_end_writer_lock(const struct btrfs_fs_info *fs_info,
84		struct page *page, u64 start, u32 len);
85
86/*
87 * Template for subpage related operations.
88 *
89 * btrfs_subpage_*() are for call sites where the page has subpage attached and
90 * the range is ensured to be inside the page.
91 *
92 * btrfs_page_*() are for call sites where the page can either be subpage
93 * specific or regular page. The function will handle both cases.
94 * But the range still needs to be inside the page.
95 *
96 * btrfs_page_clamp_*() are similar to btrfs_page_*(), except the range doesn't
97 * need to be inside the page. Those functions will truncate the range
98 * automatically.
99 */
100#define DECLARE_BTRFS_SUBPAGE_OPS(name)					\
101void btrfs_subpage_set_##name(const struct btrfs_fs_info *fs_info,	\
102		struct page *page, u64 start, u32 len);			\
103void btrfs_subpage_clear_##name(const struct btrfs_fs_info *fs_info,	\
104		struct page *page, u64 start, u32 len);			\
105bool btrfs_subpage_test_##name(const struct btrfs_fs_info *fs_info,	\
106		struct page *page, u64 start, u32 len);			\
107void btrfs_page_set_##name(const struct btrfs_fs_info *fs_info,		\
108		struct page *page, u64 start, u32 len);			\
109void btrfs_page_clear_##name(const struct btrfs_fs_info *fs_info,	\
110		struct page *page, u64 start, u32 len);			\
111bool btrfs_page_test_##name(const struct btrfs_fs_info *fs_info,	\
112		struct page *page, u64 start, u32 len);			\
113void btrfs_page_clamp_set_##name(const struct btrfs_fs_info *fs_info,	\
114		struct page *page, u64 start, u32 len);			\
115void btrfs_page_clamp_clear_##name(const struct btrfs_fs_info *fs_info,	\
116		struct page *page, u64 start, u32 len);			\
117bool btrfs_page_clamp_test_##name(const struct btrfs_fs_info *fs_info,	\
118		struct page *page, u64 start, u32 len);
119
120DECLARE_BTRFS_SUBPAGE_OPS(uptodate);
121DECLARE_BTRFS_SUBPAGE_OPS(error);
122DECLARE_BTRFS_SUBPAGE_OPS(dirty);
123DECLARE_BTRFS_SUBPAGE_OPS(writeback);
124DECLARE_BTRFS_SUBPAGE_OPS(ordered);
125
126bool btrfs_subpage_clear_and_test_dirty(const struct btrfs_fs_info *fs_info,
127		struct page *page, u64 start, u32 len);
128
129void btrfs_page_assert_not_dirty(const struct btrfs_fs_info *fs_info,
130				 struct page *page);
131
132#endif
133