fs/btrfs/subpage.h

0001 /* SPDX-License-Identifier: GPL-2.0 */
0002
0003 #ifndef BTRFS_SUBPAGE_H
0004 #define BTRFS_SUBPAGE_H
0005
0006 #include <linux/spinlock.h>
0007
0008 /*
0009  * Extra info for subpapge bitmap.
0010  *
0011  * For subpage we pack all uptodate/error/dirty/writeback/ordered bitmaps into
0012  * one larger bitmap.
0013  *
0014  * This structure records how they are organized in the bitmap:
0015  *
0016  * /- uptodate_offset   /- error_offset /- dirty_offset
0017  * |            |       |
0018  * v            v       v
0019  * |u|u|u|u|........|u|u|e|e|.......|e|e| ...   |o|o|
0020  * |<- bitmap_nr_bits ->|
0021  * |<--------------- total_nr_bits ---------------->|
0022  */
0023 struct btrfs_subpage_info {
0024     /* Number of bits for each bitmap */
0025     unsigned int bitmap_nr_bits;
0026
0027     /* Total number of bits for the whole bitmap */
0028     unsigned int total_nr_bits;
0029
0030     /*
0031      * *_start indicates where the bitmap starts, the length is always
0032      * @bitmap_size, which is calculated from PAGE_SIZE / sectorsize.
0033      */
0034     unsigned int uptodate_offset;
0035     unsigned int error_offset;
0036     unsigned int dirty_offset;
0037     unsigned int writeback_offset;
0038     unsigned int ordered_offset;
0039     unsigned int checked_offset;
0040 };
0041
0042 /*
0043  * Structure to trace status of each sector inside a page, attached to
0044  * page::private for both data and metadata inodes.
0045  */
0046 struct btrfs_subpage {
0047     /* Common members for both data and metadata pages */
0048     spinlock_t lock;
0049     /*
0050      * Both data and metadata needs to track how many readers are for the
0051      * page.
0052      * Data relies on @readers to unlock the page when last reader finished.
0053      * While metadata doesn't need page unlock, it needs to prevent
0054      * page::private get cleared before the last end_page_read().
0055      */
0056     atomic_t readers;
0057     union {
0058         /*
0059          * Structures only used by metadata
0060          *
0061          * @eb_refs should only be operated under private_lock, as it
0062          * manages whether the subpage can be detached.
0063          */
0064         atomic_t eb_refs;
0065
0066         /* Structures only used by data */
0067         atomic_t writers;
0068     };
0069     unsigned long bitmaps[];
0070 };
0071
0072 enum btrfs_subpage_type {
0073     BTRFS_SUBPAGE_METADATA,
0074     BTRFS_SUBPAGE_DATA,
0075 };
0076
0077 bool btrfs_is_subpage(const struct btrfs_fs_info *fs_info, struct page *page);
0078
0079 void btrfs_init_subpage_info(struct btrfs_subpage_info *subpage_info, u32 sectorsize);
0080 int btrfs_attach_subpage(const struct btrfs_fs_info *fs_info,
0081              struct page *page, enum btrfs_subpage_type type);
0082 void btrfs_detach_subpage(const struct btrfs_fs_info *fs_info,
0083               struct page *page);
0084
0085 /* Allocate additional data where page represents more than one sector */
0086 struct btrfs_subpage *btrfs_alloc_subpage(const struct btrfs_fs_info *fs_info,
0087                       enum btrfs_subpage_type type);
0088 void btrfs_free_subpage(struct btrfs_subpage *subpage);
0089
0090 void btrfs_page_inc_eb_refs(const struct btrfs_fs_info *fs_info,
0091                 struct page *page);
0092 void btrfs_page_dec_eb_refs(const struct btrfs_fs_info *fs_info,
0093                 struct page *page);
0094
0095 void btrfs_subpage_start_reader(const struct btrfs_fs_info *fs_info,
0096         struct page *page, u64 start, u32 len);
0097 void btrfs_subpage_end_reader(const struct btrfs_fs_info *fs_info,
0098         struct page *page, u64 start, u32 len);
0099
0100 void btrfs_subpage_start_writer(const struct btrfs_fs_info *fs_info,
0101         struct page *page, u64 start, u32 len);
0102 bool btrfs_subpage_end_and_test_writer(const struct btrfs_fs_info *fs_info,
0103         struct page *page, u64 start, u32 len);
0104 int btrfs_page_start_writer_lock(const struct btrfs_fs_info *fs_info,
0105         struct page *page, u64 start, u32 len);
0106 void btrfs_page_end_writer_lock(const struct btrfs_fs_info *fs_info,
0107         struct page *page, u64 start, u32 len);
0108
0109 /*
0110  * Template for subpage related operations.
0111  *
0112  * btrfs_subpage_*() are for call sites where the page has subpage attached and
0113  * the range is ensured to be inside the page.
0114  *
0115  * btrfs_page_*() are for call sites where the page can either be subpage
0116  * specific or regular page. The function will handle both cases.
0117  * But the range still needs to be inside the page.
0118  *
0119  * btrfs_page_clamp_*() are similar to btrfs_page_*(), except the range doesn't
0120  * need to be inside the page. Those functions will truncate the range
0121  * automatically.
0122  */
0123 #define DECLARE_BTRFS_SUBPAGE_OPS(name)                 \
0124 void btrfs_subpage_set_##name(const struct btrfs_fs_info *fs_info,  \
0125         struct page *page, u64 start, u32 len);         \
0126 void btrfs_subpage_clear_##name(const struct btrfs_fs_info *fs_info,    \
0127         struct page *page, u64 start, u32 len);         \
0128 bool btrfs_subpage_test_##name(const struct btrfs_fs_info *fs_info, \
0129         struct page *page, u64 start, u32 len);         \
0130 void btrfs_page_set_##name(const struct btrfs_fs_info *fs_info,     \
0131         struct page *page, u64 start, u32 len);         \
0132 void btrfs_page_clear_##name(const struct btrfs_fs_info *fs_info,   \
0133         struct page *page, u64 start, u32 len);         \
0134 bool btrfs_page_test_##name(const struct btrfs_fs_info *fs_info,    \
0135         struct page *page, u64 start, u32 len);         \
0136 void btrfs_page_clamp_set_##name(const struct btrfs_fs_info *fs_info,   \
0137         struct page *page, u64 start, u32 len);         \
0138 void btrfs_page_clamp_clear_##name(const struct btrfs_fs_info *fs_info, \
0139         struct page *page, u64 start, u32 len);         \
0140 bool btrfs_page_clamp_test_##name(const struct btrfs_fs_info *fs_info,  \
0141         struct page *page, u64 start, u32 len);
0142
0143 DECLARE_BTRFS_SUBPAGE_OPS(uptodate);
0144 DECLARE_BTRFS_SUBPAGE_OPS(error);
0145 DECLARE_BTRFS_SUBPAGE_OPS(dirty);
0146 DECLARE_BTRFS_SUBPAGE_OPS(writeback);
0147 DECLARE_BTRFS_SUBPAGE_OPS(ordered);
0148 DECLARE_BTRFS_SUBPAGE_OPS(checked);
0149
0150 bool btrfs_subpage_clear_and_test_dirty(const struct btrfs_fs_info *fs_info,
0151         struct page *page, u64 start, u32 len);
0152
0153 void btrfs_page_assert_not_dirty(const struct btrfs_fs_info *fs_info,
0154                  struct page *page);
0155 void btrfs_page_unlock_writer(struct btrfs_fs_info *fs_info, struct page *page,
0156                   u64 start, u32 len);
0157
0158 #endif