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![Qu Wenruo](/assets/img/avatar_default.png)
The reason why we only support 64K page size for subpage is, for 64K page size we can ensure no matter what the nodesize is, we can fit it into one page. When other page size come, especially like 16K, the limitation is a bit limiting. To remove such limitation, we allow nodesize >= PAGE_SIZE case to go the non-subpage routine. By this, we can allow 4K sectorsize on 16K page size. Although this introduces another smaller limitation, the metadata can not cross page boundary, which is already met by most recent mkfs. Another small improvement is, we can avoid the overhead for metadata if nodesize >= PAGE_SIZE. For 4K sector size and 64K page size/node size, or 4K sector size and 16K page size/node size, we don't need to allocate extra memory for the metadata pages. Please note that, this patch will not yet enable other page size support yet. Signed-off-by: Qu Wenruo <wqu@suse.com> Reviewed-by: David Sterba <dsterba@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
158 lines
5.5 KiB
C
158 lines
5.5 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef BTRFS_SUBPAGE_H
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#define BTRFS_SUBPAGE_H
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#include <linux/spinlock.h>
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/*
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* Extra info for subpapge bitmap.
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*
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* For subpage we pack all uptodate/error/dirty/writeback/ordered bitmaps into
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* one larger bitmap.
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*
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* This structure records how they are organized in the bitmap:
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*
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* /- uptodate_offset /- error_offset /- dirty_offset
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* | | |
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* v v v
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* |u|u|u|u|........|u|u|e|e|.......|e|e| ... |o|o|
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* |<- bitmap_nr_bits ->|
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* |<--------------- total_nr_bits ---------------->|
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*/
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struct btrfs_subpage_info {
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/* Number of bits for each bitmap */
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unsigned int bitmap_nr_bits;
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/* Total number of bits for the whole bitmap */
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unsigned int total_nr_bits;
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/*
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* *_start indicates where the bitmap starts, the length is always
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* @bitmap_size, which is calculated from PAGE_SIZE / sectorsize.
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*/
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unsigned int uptodate_offset;
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unsigned int error_offset;
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unsigned int dirty_offset;
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unsigned int writeback_offset;
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unsigned int ordered_offset;
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unsigned int checked_offset;
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};
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/*
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* Structure to trace status of each sector inside a page, attached to
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* page::private for both data and metadata inodes.
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*/
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struct btrfs_subpage {
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/* Common members for both data and metadata pages */
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spinlock_t lock;
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/*
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* Both data and metadata needs to track how many readers are for the
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* page.
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* Data relies on @readers to unlock the page when last reader finished.
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* While metadata doesn't need page unlock, it needs to prevent
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* page::private get cleared before the last end_page_read().
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*/
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atomic_t readers;
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union {
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/*
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* Structures only used by metadata
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*
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* @eb_refs should only be operated under private_lock, as it
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* manages whether the subpage can be detached.
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*/
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atomic_t eb_refs;
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/* Structures only used by data */
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atomic_t writers;
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};
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unsigned long bitmaps[];
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};
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enum btrfs_subpage_type {
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BTRFS_SUBPAGE_METADATA,
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BTRFS_SUBPAGE_DATA,
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};
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bool btrfs_is_subpage(const struct btrfs_fs_info *fs_info, struct page *page);
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void btrfs_init_subpage_info(struct btrfs_subpage_info *subpage_info, u32 sectorsize);
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int btrfs_attach_subpage(const struct btrfs_fs_info *fs_info,
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struct page *page, enum btrfs_subpage_type type);
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void btrfs_detach_subpage(const struct btrfs_fs_info *fs_info,
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struct page *page);
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/* Allocate additional data where page represents more than one sector */
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struct btrfs_subpage *btrfs_alloc_subpage(const struct btrfs_fs_info *fs_info,
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enum btrfs_subpage_type type);
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void btrfs_free_subpage(struct btrfs_subpage *subpage);
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void btrfs_page_inc_eb_refs(const struct btrfs_fs_info *fs_info,
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struct page *page);
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void btrfs_page_dec_eb_refs(const struct btrfs_fs_info *fs_info,
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struct page *page);
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void btrfs_subpage_start_reader(const struct btrfs_fs_info *fs_info,
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struct page *page, u64 start, u32 len);
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void btrfs_subpage_end_reader(const struct btrfs_fs_info *fs_info,
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struct page *page, u64 start, u32 len);
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void btrfs_subpage_start_writer(const struct btrfs_fs_info *fs_info,
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struct page *page, u64 start, u32 len);
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bool btrfs_subpage_end_and_test_writer(const struct btrfs_fs_info *fs_info,
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struct page *page, u64 start, u32 len);
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int btrfs_page_start_writer_lock(const struct btrfs_fs_info *fs_info,
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struct page *page, u64 start, u32 len);
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void btrfs_page_end_writer_lock(const struct btrfs_fs_info *fs_info,
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struct page *page, u64 start, u32 len);
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/*
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* Template for subpage related operations.
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*
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* btrfs_subpage_*() are for call sites where the page has subpage attached and
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* the range is ensured to be inside the page.
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*
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* btrfs_page_*() are for call sites where the page can either be subpage
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* specific or regular page. The function will handle both cases.
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* But the range still needs to be inside the page.
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*
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* btrfs_page_clamp_*() are similar to btrfs_page_*(), except the range doesn't
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* need to be inside the page. Those functions will truncate the range
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* automatically.
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*/
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#define DECLARE_BTRFS_SUBPAGE_OPS(name) \
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void btrfs_subpage_set_##name(const struct btrfs_fs_info *fs_info, \
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struct page *page, u64 start, u32 len); \
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void btrfs_subpage_clear_##name(const struct btrfs_fs_info *fs_info, \
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struct page *page, u64 start, u32 len); \
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bool btrfs_subpage_test_##name(const struct btrfs_fs_info *fs_info, \
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struct page *page, u64 start, u32 len); \
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void btrfs_page_set_##name(const struct btrfs_fs_info *fs_info, \
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struct page *page, u64 start, u32 len); \
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void btrfs_page_clear_##name(const struct btrfs_fs_info *fs_info, \
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struct page *page, u64 start, u32 len); \
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bool btrfs_page_test_##name(const struct btrfs_fs_info *fs_info, \
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struct page *page, u64 start, u32 len); \
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void btrfs_page_clamp_set_##name(const struct btrfs_fs_info *fs_info, \
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struct page *page, u64 start, u32 len); \
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void btrfs_page_clamp_clear_##name(const struct btrfs_fs_info *fs_info, \
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struct page *page, u64 start, u32 len); \
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bool btrfs_page_clamp_test_##name(const struct btrfs_fs_info *fs_info, \
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struct page *page, u64 start, u32 len);
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DECLARE_BTRFS_SUBPAGE_OPS(uptodate);
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DECLARE_BTRFS_SUBPAGE_OPS(error);
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DECLARE_BTRFS_SUBPAGE_OPS(dirty);
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DECLARE_BTRFS_SUBPAGE_OPS(writeback);
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DECLARE_BTRFS_SUBPAGE_OPS(ordered);
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DECLARE_BTRFS_SUBPAGE_OPS(checked);
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bool btrfs_subpage_clear_and_test_dirty(const struct btrfs_fs_info *fs_info,
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struct page *page, u64 start, u32 len);
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void btrfs_page_assert_not_dirty(const struct btrfs_fs_info *fs_info,
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struct page *page);
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void btrfs_page_unlock_writer(struct btrfs_fs_info *fs_info, struct page *page,
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u64 start, u32 len);
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#endif
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