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-rw-r--r--fs/btrfs/subpage.h158
1 files changed, 158 insertions, 0 deletions
diff --git a/fs/btrfs/subpage.h b/fs/btrfs/subpage.h
new file mode 100644
index 000000000..0e80ad336
--- /dev/null
+++ b/fs/btrfs/subpage.h
@@ -0,0 +1,158 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+
+#ifndef BTRFS_SUBPAGE_H
+#define BTRFS_SUBPAGE_H
+
+#include <linux/spinlock.h>
+
+/*
+ * Extra info for subpapge bitmap.
+ *
+ * For subpage we pack all uptodate/error/dirty/writeback/ordered bitmaps into
+ * one larger bitmap.
+ *
+ * This structure records how they are organized in the bitmap:
+ *
+ * /- uptodate_offset /- error_offset /- dirty_offset
+ * | | |
+ * v v v
+ * |u|u|u|u|........|u|u|e|e|.......|e|e| ... |o|o|
+ * |<- bitmap_nr_bits ->|
+ * |<--------------- total_nr_bits ---------------->|
+ */
+struct btrfs_subpage_info {
+ /* Number of bits for each bitmap */
+ unsigned int bitmap_nr_bits;
+
+ /* Total number of bits for the whole bitmap */
+ unsigned int total_nr_bits;
+
+ /*
+ * *_start indicates where the bitmap starts, the length is always
+ * @bitmap_size, which is calculated from PAGE_SIZE / sectorsize.
+ */
+ unsigned int uptodate_offset;
+ unsigned int error_offset;
+ unsigned int dirty_offset;
+ unsigned int writeback_offset;
+ unsigned int ordered_offset;
+ unsigned int checked_offset;
+};
+
+/*
+ * Structure to trace status of each sector inside a page, attached to
+ * page::private for both data and metadata inodes.
+ */
+struct btrfs_subpage {
+ /* Common members for both data and metadata pages */
+ spinlock_t lock;
+ /*
+ * Both data and metadata needs to track how many readers are for the
+ * page.
+ * Data relies on @readers to unlock the page when last reader finished.
+ * While metadata doesn't need page unlock, it needs to prevent
+ * page::private get cleared before the last end_page_read().
+ */
+ atomic_t readers;
+ union {
+ /*
+ * Structures only used by metadata
+ *
+ * @eb_refs should only be operated under private_lock, as it
+ * manages whether the subpage can be detached.
+ */
+ atomic_t eb_refs;
+
+ /* Structures only used by data */
+ atomic_t writers;
+ };
+ unsigned long bitmaps[];
+};
+
+enum btrfs_subpage_type {
+ BTRFS_SUBPAGE_METADATA,
+ BTRFS_SUBPAGE_DATA,
+};
+
+bool btrfs_is_subpage(const struct btrfs_fs_info *fs_info, struct page *page);
+
+void btrfs_init_subpage_info(struct btrfs_subpage_info *subpage_info, u32 sectorsize);
+int btrfs_attach_subpage(const struct btrfs_fs_info *fs_info,
+ struct page *page, enum btrfs_subpage_type type);
+void btrfs_detach_subpage(const struct btrfs_fs_info *fs_info,
+ struct page *page);
+
+/* Allocate additional data where page represents more than one sector */
+struct btrfs_subpage *btrfs_alloc_subpage(const struct btrfs_fs_info *fs_info,
+ enum btrfs_subpage_type type);
+void btrfs_free_subpage(struct btrfs_subpage *subpage);
+
+void btrfs_page_inc_eb_refs(const struct btrfs_fs_info *fs_info,
+ struct page *page);
+void btrfs_page_dec_eb_refs(const struct btrfs_fs_info *fs_info,
+ struct page *page);
+
+void btrfs_subpage_start_reader(const struct btrfs_fs_info *fs_info,
+ struct page *page, u64 start, u32 len);
+void btrfs_subpage_end_reader(const struct btrfs_fs_info *fs_info,
+ struct page *page, u64 start, u32 len);
+
+void btrfs_subpage_start_writer(const struct btrfs_fs_info *fs_info,
+ struct page *page, u64 start, u32 len);
+bool btrfs_subpage_end_and_test_writer(const struct btrfs_fs_info *fs_info,
+ struct page *page, u64 start, u32 len);
+int btrfs_page_start_writer_lock(const struct btrfs_fs_info *fs_info,
+ struct page *page, u64 start, u32 len);
+void btrfs_page_end_writer_lock(const struct btrfs_fs_info *fs_info,
+ struct page *page, u64 start, u32 len);
+
+/*
+ * Template for subpage related operations.
+ *
+ * btrfs_subpage_*() are for call sites where the page has subpage attached and
+ * the range is ensured to be inside the page.
+ *
+ * btrfs_page_*() are for call sites where the page can either be subpage
+ * specific or regular page. The function will handle both cases.
+ * But the range still needs to be inside the page.
+ *
+ * btrfs_page_clamp_*() are similar to btrfs_page_*(), except the range doesn't
+ * need to be inside the page. Those functions will truncate the range
+ * automatically.
+ */
+#define DECLARE_BTRFS_SUBPAGE_OPS(name) \
+void btrfs_subpage_set_##name(const struct btrfs_fs_info *fs_info, \
+ struct page *page, u64 start, u32 len); \
+void btrfs_subpage_clear_##name(const struct btrfs_fs_info *fs_info, \
+ struct page *page, u64 start, u32 len); \
+bool btrfs_subpage_test_##name(const struct btrfs_fs_info *fs_info, \
+ struct page *page, u64 start, u32 len); \
+void btrfs_page_set_##name(const struct btrfs_fs_info *fs_info, \
+ struct page *page, u64 start, u32 len); \
+void btrfs_page_clear_##name(const struct btrfs_fs_info *fs_info, \
+ struct page *page, u64 start, u32 len); \
+bool btrfs_page_test_##name(const struct btrfs_fs_info *fs_info, \
+ struct page *page, u64 start, u32 len); \
+void btrfs_page_clamp_set_##name(const struct btrfs_fs_info *fs_info, \
+ struct page *page, u64 start, u32 len); \
+void btrfs_page_clamp_clear_##name(const struct btrfs_fs_info *fs_info, \
+ struct page *page, u64 start, u32 len); \
+bool btrfs_page_clamp_test_##name(const struct btrfs_fs_info *fs_info, \
+ struct page *page, u64 start, u32 len);
+
+DECLARE_BTRFS_SUBPAGE_OPS(uptodate);
+DECLARE_BTRFS_SUBPAGE_OPS(error);
+DECLARE_BTRFS_SUBPAGE_OPS(dirty);
+DECLARE_BTRFS_SUBPAGE_OPS(writeback);
+DECLARE_BTRFS_SUBPAGE_OPS(ordered);
+DECLARE_BTRFS_SUBPAGE_OPS(checked);
+
+bool btrfs_subpage_clear_and_test_dirty(const struct btrfs_fs_info *fs_info,
+ struct page *page, u64 start, u32 len);
+
+void btrfs_page_assert_not_dirty(const struct btrfs_fs_info *fs_info,
+ struct page *page);
+void btrfs_page_unlock_writer(struct btrfs_fs_info *fs_info, struct page *page,
+ u64 start, u32 len);
+
+#endif