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/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	/- dirty_offset	/- ordered_offset
 17 * |			|		|
 18 * v			v		v
 19 * |u|u|u|u|........|u|u|d|d|.......|d|d|o|o|.......|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 dirty_offset;
 36	unsigned int writeback_offset;
 37	unsigned int ordered_offset;
 38	unsigned int checked_offset;
 39};
 40
 41/*
 42 * Structure to trace status of each sector inside a page, attached to
 43 * page::private for both data and metadata inodes.
 44 */
 45struct btrfs_subpage {
 46	/* Common members for both data and metadata pages */
 47	spinlock_t lock;
 48	/*
 49	 * Both data and metadata needs to track how many readers are for the
 50	 * page.
 51	 * Data relies on @readers to unlock the page when last reader finished.
 52	 * While metadata doesn't need page unlock, it needs to prevent
 53	 * page::private get cleared before the last end_page_read().
 54	 */
 55	atomic_t readers;
 56	union {
 57		/*
 58		 * Structures only used by metadata
 59		 *
 60		 * @eb_refs should only be operated under private_lock, as it
 61		 * manages whether the subpage can be detached.
 62		 */
 63		atomic_t eb_refs;
 64
 65		/* Structures only used by data */
 66		atomic_t writers;
 67	};
 68	unsigned long bitmaps[];
 69};
 70
 71enum btrfs_subpage_type {
 72	BTRFS_SUBPAGE_METADATA,
 73	BTRFS_SUBPAGE_DATA,
 74};
 75
 76bool btrfs_is_subpage(const struct btrfs_fs_info *fs_info, struct address_space *mapping);
 77
 78void btrfs_init_subpage_info(struct btrfs_subpage_info *subpage_info, u32 sectorsize);
 79int btrfs_attach_subpage(const struct btrfs_fs_info *fs_info,
 80			 struct folio *folio, enum btrfs_subpage_type type);
 81void btrfs_detach_subpage(const struct btrfs_fs_info *fs_info, struct folio *folio);
 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_folio_inc_eb_refs(const struct btrfs_fs_info *fs_info, struct folio *folio);
 89void btrfs_folio_dec_eb_refs(const struct btrfs_fs_info *fs_info, struct folio *folio);
 90
 91void btrfs_subpage_start_reader(const struct btrfs_fs_info *fs_info,
 92				struct folio *folio, u64 start, u32 len);
 93void btrfs_subpage_end_reader(const struct btrfs_fs_info *fs_info,
 94			      struct folio *folio, u64 start, u32 len);
 95
 96void btrfs_subpage_start_writer(const struct btrfs_fs_info *fs_info,
 97				struct folio *folio, u64 start, u32 len);
 98bool btrfs_subpage_end_and_test_writer(const struct btrfs_fs_info *fs_info,
 99				       struct folio *folio, u64 start, u32 len);
100int btrfs_folio_start_writer_lock(const struct btrfs_fs_info *fs_info,
101				  struct folio *folio, u64 start, u32 len);
102void btrfs_folio_end_writer_lock(const struct btrfs_fs_info *fs_info,
103				 struct folio *folio, u64 start, u32 len);
104
105/*
106 * Template for subpage related operations.
107 *
108 * btrfs_subpage_*() are for call sites where the folio has subpage attached and
109 * the range is ensured to be inside the folio's single page.
110 *
111 * btrfs_folio_*() are for call sites where the page can either be subpage
112 * specific or regular folios. The function will handle both cases.
113 * But the range still needs to be inside one single page.
114 *
115 * btrfs_folio_clamp_*() are similar to btrfs_folio_*(), except the range doesn't
116 * need to be inside the page. Those functions will truncate the range
117 * automatically.
118 */
119#define DECLARE_BTRFS_SUBPAGE_OPS(name)					\
120void btrfs_subpage_set_##name(const struct btrfs_fs_info *fs_info,	\
121		struct folio *folio, u64 start, u32 len);			\
122void btrfs_subpage_clear_##name(const struct btrfs_fs_info *fs_info,	\
123		struct folio *folio, u64 start, u32 len);			\
124bool btrfs_subpage_test_##name(const struct btrfs_fs_info *fs_info,	\
125		struct folio *folio, u64 start, u32 len);			\
126void btrfs_folio_set_##name(const struct btrfs_fs_info *fs_info,	\
127		struct folio *folio, u64 start, u32 len);			\
128void btrfs_folio_clear_##name(const struct btrfs_fs_info *fs_info,	\
129		struct folio *folio, u64 start, u32 len);			\
130bool btrfs_folio_test_##name(const struct btrfs_fs_info *fs_info,	\
131		struct folio *folio, u64 start, u32 len);			\
132void btrfs_folio_clamp_set_##name(const struct btrfs_fs_info *fs_info,	\
133		struct folio *folio, u64 start, u32 len);			\
134void btrfs_folio_clamp_clear_##name(const struct btrfs_fs_info *fs_info,	\
135		struct folio *folio, u64 start, u32 len);			\
136bool btrfs_folio_clamp_test_##name(const struct btrfs_fs_info *fs_info,	\
137		struct folio *folio, u64 start, u32 len);
138
139DECLARE_BTRFS_SUBPAGE_OPS(uptodate);
140DECLARE_BTRFS_SUBPAGE_OPS(dirty);
141DECLARE_BTRFS_SUBPAGE_OPS(writeback);
142DECLARE_BTRFS_SUBPAGE_OPS(ordered);
143DECLARE_BTRFS_SUBPAGE_OPS(checked);
144
145bool btrfs_subpage_clear_and_test_dirty(const struct btrfs_fs_info *fs_info,
146					struct folio *folio, u64 start, u32 len);
147
148void btrfs_folio_assert_not_dirty(const struct btrfs_fs_info *fs_info, struct folio *folio);
149void btrfs_folio_unlock_writer(struct btrfs_fs_info *fs_info,
150			       struct folio *folio, u64 start, u32 len);
151void __cold btrfs_subpage_dump_bitmap(const struct btrfs_fs_info *fs_info,
152				      struct folio *folio, u64 start, u32 len);
153
154#endif