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Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
62 lines
2.1 KiB
C
62 lines
2.1 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef _BCACHEFS_SNAPSHOT_FORMAT_H
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#define _BCACHEFS_SNAPSHOT_FORMAT_H
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struct bch_snapshot {
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struct bch_val v;
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__le32 flags;
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__le32 parent;
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__le32 children[2];
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__le32 subvol;
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/* corresponds to a bch_snapshot_tree in BTREE_ID_snapshot_trees */
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__le32 tree;
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__le32 depth;
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__le32 skip[3];
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bch_le128 btime;
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};
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/*
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* WILL_DELETE: leaf node that's no longer referenced by a subvolume, still has
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* keys, will be deleted by delete_dead_snapshots
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*
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* SUBVOL: true if a subvol points to this snapshot (why do we have this?
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* subvols are nonzero)
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*
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* DELETED: we never delete snapshot keys, we mark them as deleted so that we
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* can distinguish between a key for a missing snapshot (and we have no idea
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* what happened) and a key for a deleted snapshot (delete_dead_snapshots() missed
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* something, key should be deleted)
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*
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* NO_KEYS: we don't remove interior snapshot nodes from snapshot trees at
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* runtime, since we can't do the adjustements for the depth/skiplist field
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* atomically - and that breaks e.g. is_ancestor(). Instead, we mark it to be
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* deleted at the next remount; this tells us that we don't need to run the full
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* delete_dead_snapshots().
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*
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*
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* XXX - todo item:
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*
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* We should guard against a bitflip causing us to delete a snapshot incorrectly
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* by cross checking with the subvolume btree: delete_dead_snapshots() can take
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* out more data than any other codepath if it runs incorrectly
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*/
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LE32_BITMASK(BCH_SNAPSHOT_WILL_DELETE, struct bch_snapshot, flags, 0, 1)
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LE32_BITMASK(BCH_SNAPSHOT_SUBVOL, struct bch_snapshot, flags, 1, 2)
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LE32_BITMASK(BCH_SNAPSHOT_DELETED, struct bch_snapshot, flags, 2, 3)
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LE32_BITMASK(BCH_SNAPSHOT_NO_KEYS, struct bch_snapshot, flags, 3, 4)
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/*
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* Snapshot trees:
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*
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* The snapshot_trees btree gives us persistent indentifier for each tree of
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* bch_snapshot nodes, and allow us to record and easily find the root/master
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* subvolume that other snapshots were created from:
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*/
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struct bch_snapshot_tree {
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struct bch_val v;
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__le32 master_subvol;
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__le32 root_snapshot;
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};
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#endif /* _BCACHEFS_SNAPSHOT_FORMAT_H */
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