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
129#endif