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To check whether a given file extent is referenced by multiple snapshots, the checker walks down the fs tree through dead root and checks all tree blocks in the path. We can easily detect whether a given tree block is directly referenced by other snapshot. We can also detect any indirect reference from other snapshot by checking reference's generation. The checker can always detect multiple references, but can't reliably detect cases of single reference. So btrfs may do file data cow even there is only one reference. Signed-off-by: Chris Mason <chris.mason@oracle.com>
101 lines
3.0 KiB
C
101 lines
3.0 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 __BTRFS_TRANSACTION__
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#define __BTRFS_TRANSACTION__
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#include "btrfs_inode.h"
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struct btrfs_transaction {
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u64 transid;
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unsigned long num_writers;
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unsigned long num_joined;
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int in_commit;
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int use_count;
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int commit_done;
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int blocked;
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struct list_head list;
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struct extent_io_tree dirty_pages;
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unsigned long start_time;
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wait_queue_head_t writer_wait;
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wait_queue_head_t commit_wait;
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struct list_head pending_snapshots;
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};
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struct btrfs_trans_handle {
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u64 transid;
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unsigned long blocks_reserved;
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unsigned long blocks_used;
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struct btrfs_transaction *transaction;
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struct btrfs_block_group_cache *block_group;
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u64 alloc_exclude_start;
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u64 alloc_exclude_nr;
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};
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struct btrfs_pending_snapshot {
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struct btrfs_root *root;
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char *name;
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struct list_head list;
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};
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struct btrfs_dirty_root {
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struct list_head list;
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struct btrfs_root *root;
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struct btrfs_root *latest_root;
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};
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static inline void btrfs_set_trans_block_group(struct btrfs_trans_handle *trans,
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struct inode *inode)
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{
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trans->block_group = BTRFS_I(inode)->block_group;
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}
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static inline void btrfs_update_inode_block_group(struct
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btrfs_trans_handle *trans,
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struct inode *inode)
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{
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BTRFS_I(inode)->block_group = trans->block_group;
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}
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static inline void btrfs_set_inode_last_trans(struct btrfs_trans_handle *trans,
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struct inode *inode)
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{
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BTRFS_I(inode)->last_trans = trans->transaction->transid;
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}
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int btrfs_end_transaction(struct btrfs_trans_handle *trans,
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struct btrfs_root *root);
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struct btrfs_trans_handle *btrfs_start_transaction(struct btrfs_root *root,
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int num_blocks);
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struct btrfs_trans_handle *btrfs_join_transaction(struct btrfs_root *root,
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int num_blocks);
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int btrfs_write_and_wait_transaction(struct btrfs_trans_handle *trans,
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struct btrfs_root *root);
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int btrfs_commit_tree_roots(struct btrfs_trans_handle *trans,
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struct btrfs_root *root);
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int btrfs_add_dead_root(struct btrfs_root *root, struct btrfs_root *latest,
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struct list_head *dead_list);
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int btrfs_defrag_root(struct btrfs_root *root, int cacheonly);
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int btrfs_clean_old_snapshots(struct btrfs_root *root);
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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_end_transaction_throttle(struct btrfs_trans_handle *trans,
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struct btrfs_root *root);
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void btrfs_throttle(struct btrfs_root *root);
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#endif
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