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// Copyright (C) 2022-2023 Luke Shumaker <lukeshu@lukeshu.com>
//
// SPDX-License-Identifier: GPL-2.0-or-later
package btrfstree
import (
"errors"
"fmt"
"git.lukeshu.com/btrfs-progs-ng/lib/btrfs/btrfsitem"
"git.lukeshu.com/btrfs-progs-ng/lib/btrfs/btrfsprim"
"git.lukeshu.com/btrfs-progs-ng/lib/btrfs/btrfsvol"
)
// A TreeRoot is more-or-less a btrfsitem.Root, but simpler; returned by
// LookupTreeRoot.
type TreeRoot struct {
TreeID btrfsprim.ObjID
RootNode btrfsvol.LogicalAddr
Level uint8
Generation btrfsprim.Generation
}
func RootItemSearchFn(treeID btrfsprim.ObjID) func(btrfsprim.Key, uint32) int {
return func(key btrfsprim.Key, _ uint32) int {
if key.ObjectID == treeID && key.ItemType == btrfsitem.ROOT_ITEM_KEY {
return 0
}
return btrfsprim.Key{
ObjectID: treeID,
ItemType: btrfsitem.ROOT_ITEM_KEY,
Offset: 0,
}.Compare(key)
}
}
// LookupTreeRoot is a utility function to help with implementing the
// 'TreeOperator' interface.
func LookupTreeRoot(fs TreeOperator, sb Superblock, treeID btrfsprim.ObjID) (*TreeRoot, error) {
switch treeID {
case btrfsprim.ROOT_TREE_OBJECTID:
return &TreeRoot{
TreeID: treeID,
RootNode: sb.RootTree,
Level: sb.RootLevel,
Generation: sb.Generation, // XXX: same generation as LOG_TREE?
}, nil
case btrfsprim.CHUNK_TREE_OBJECTID:
return &TreeRoot{
TreeID: treeID,
RootNode: sb.ChunkTree,
Level: sb.ChunkLevel,
Generation: sb.ChunkRootGeneration,
}, nil
case btrfsprim.TREE_LOG_OBJECTID:
return &TreeRoot{
TreeID: treeID,
RootNode: sb.LogTree,
Level: sb.LogLevel,
Generation: sb.Generation, // XXX: same generation as ROOT_TREE?
}, nil
case btrfsprim.BLOCK_GROUP_TREE_OBJECTID:
return &TreeRoot{
TreeID: treeID,
RootNode: sb.BlockGroupRoot,
Level: sb.BlockGroupRootLevel,
Generation: sb.BlockGroupRootGeneration,
}, nil
default:
rootItem, err := fs.TreeSearch(btrfsprim.ROOT_TREE_OBJECTID, RootItemSearchFn(treeID))
if err != nil {
if errors.Is(err, ErrNoItem) {
err = ErrNoTree
}
return nil, err
}
switch rootItemBody := rootItem.Body.(type) {
case *btrfsitem.Root:
return &TreeRoot{
TreeID: treeID,
RootNode: rootItemBody.ByteNr,
Level: rootItemBody.Level,
Generation: rootItemBody.Generation,
}, nil
case *btrfsitem.Error:
return nil, fmt.Errorf("malformed ROOT_ITEM for tree %v: %w", treeID, rootItemBody.Err)
default:
panic(fmt.Errorf("should not happen: ROOT_ITEM has unexpected item type: %T", rootItemBody))
}
}
}
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