95d3f20b51
This commit introduces a new kind of back reference for btrfs metadata. Once a filesystem has been mounted with this commit, IT WILL NO LONGER BE MOUNTABLE BY OLDER KERNELS. The new back ref provides information about pointer's key, level and in which tree the pointer lives. This information allow us to find the pointer by searching the tree. The shortcoming of the new back ref is that it only works for pointers in tree blocks referenced by their owner trees. This is mostly a problem for snapshots, where resolving one of these fuzzy back references would be O(number_of_snapshots) and quite slow. The solution used here is to use the fuzzy back references in the common case where a given tree block is only referenced by one root, and use the full back references when multiple roots have a reference
79 lines
3.2 KiB
C
79 lines
3.2 KiB
C
/*
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* Copyright (C) 2007 Oracle. All rights reserved.
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public
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* License v2 as published by the Free Software Foundation.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* General Public License for more details.
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*
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* You should have received a copy of the GNU General Public
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* License along with this program; if not, write to the
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* Free Software Foundation, Inc., 59 Temple Place - Suite 330,
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* Boston, MA 021110-1307, USA.
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*/
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#ifndef __DISKIO__
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#define __DISKIO__
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#define BTRFS_SUPER_INFO_OFFSET (64 * 1024)
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#define BTRFS_SUPER_INFO_SIZE 4096
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#define BTRFS_SUPER_MIRROR_MAX 3
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#define BTRFS_SUPER_MIRROR_SHIFT 12
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static inline u64 btrfs_sb_offset(int mirror)
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{
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u64 start = 16 * 1024;
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if (mirror)
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return start << (BTRFS_SUPER_MIRROR_SHIFT * mirror);
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return BTRFS_SUPER_INFO_OFFSET;
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}
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struct btrfs_device;
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struct extent_buffer *read_tree_block(struct btrfs_root *root, u64 bytenr,
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u32 blocksize, u64 parent_transid);
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int readahead_tree_block(struct btrfs_root *root, u64 bytenr, u32 blocksize,
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u64 parent_transid);
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struct extent_buffer *btrfs_find_create_tree_block(struct btrfs_root *root,
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u64 bytenr, u32 blocksize);
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int clean_tree_block(struct btrfs_trans_handle *trans,
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struct btrfs_root *root, struct extent_buffer *buf);
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struct btrfs_root *open_ctree(const char *filename, u64 sb_bytenr, int writes);
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struct btrfs_root *open_ctree_fd(int fp, const char *path, u64 sb_bytenr,
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int writes);
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int close_ctree(struct btrfs_root *root);
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int write_ctree_super(struct btrfs_trans_handle *trans,
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struct btrfs_root *root);
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int btrfs_read_dev_super(int fd, struct btrfs_super_block *sb, u64 sb_bytenr);
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int btrfs_map_bh_to_logical(struct btrfs_root *root, struct extent_buffer *bh,
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u64 logical);
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struct extent_buffer *btrfs_find_tree_block(struct btrfs_root *root,
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u64 bytenr, u32 blocksize);
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struct btrfs_root *btrfs_read_fs_root(struct btrfs_fs_info *fs_info,
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struct btrfs_key *location);
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struct btrfs_root *btrfs_read_fs_root_no_cache(struct btrfs_fs_info *fs_info,
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struct btrfs_key *location);
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int btrfs_free_fs_root(struct btrfs_fs_info *fs_info, struct btrfs_root *root);
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void btrfs_mark_buffer_dirty(struct extent_buffer *buf);
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int btrfs_buffer_uptodate(struct extent_buffer *buf, u64 parent_transid);
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int btrfs_set_buffer_uptodate(struct extent_buffer *buf);
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int wait_on_tree_block_writeback(struct btrfs_root *root,
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struct extent_buffer *buf);
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u32 btrfs_csum_data(struct btrfs_root *root, char *data, u32 seed, size_t len);
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void btrfs_csum_final(u32 crc, char *result);
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int btrfs_commit_transaction(struct btrfs_trans_handle *trans,
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struct btrfs_root *root);
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int btrfs_open_device(struct btrfs_device *dev);
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int csum_tree_block_size(struct extent_buffer *buf, u16 csum_sectorsize,
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int verify);
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int csum_tree_block(struct btrfs_root *root, struct extent_buffer *buf,
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int verify);
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int btrfs_read_buffer(struct extent_buffer *buf, u64 parent_transid);
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#endif
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