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// Copyright (C) 2022-2023 Luke Shumaker <lukeshu@lukeshu.com>
//
// SPDX-License-Identifier: GPL-2.0-or-later
package btrfstree
import (
"fmt"
"git.lukeshu.com/btrfs-progs-ng/lib/btrfs/btrfsprim"
"git.lukeshu.com/btrfs-progs-ng/lib/btrfs/btrfsvol"
"git.lukeshu.com/btrfs-progs-ng/lib/containers"
"git.lukeshu.com/btrfs-progs-ng/lib/diskio"
)
type NodeFile interface {
diskio.ReaderAt[btrfsvol.LogicalAddr]
// ParentTree, given a tree ID, returns that tree's parent
// tree, if it has one.
//
// - non-zero, ?, true : the parent tree ID
//
// - 0, 0, true : the tree does not have a parent
//
// - ?, ?, false : the tree's parent information could not be
// looked up
ParentTree(btrfsprim.ObjID) (btrfsprim.ObjID, btrfsprim.Generation, bool)
}
// NodeExpectations returns the address to read and the expectations
// to have when reading the node pointed to by this Path.
//
// `ok` is false if the path is empty or if this Path points to an
// item rather than a node.
func (path Path) NodeExpectations(fs NodeFile) (_ btrfsvol.LogicalAddr, _ NodeExpectations, ok bool) {
if path.Node(-1).ToNodeAddr == 0 && path.Node(-1).ToNodeGeneration == 0 && path.Node(-1).ToNodeLevel == 0 {
return 0, NodeExpectations{}, false
}
checkOwner := func(owner btrfsprim.ObjID, gen btrfsprim.Generation) error {
var treeParents []btrfsprim.ObjID
tree := path.Node(-1).FromTree
for {
if owner == tree {
// OK!
return nil
}
treeParents = append(treeParents, tree)
parent, parentGen, parentOK := fs.ParentTree(tree)
if !parentOK {
// Failed look up parent info; fail open.
return nil
}
if parent == 0 {
// End of the line.
return fmt.Errorf("expected owner in %v but claims to have owner=%v",
treeParents, owner)
}
if gen > parentGen {
return fmt.Errorf("claimed owner=%v might be acceptable in this tree (if generation<=%v) but not with claimed generation=%v",
owner, parentGen, gen)
}
tree = parent
}
}
return path.Node(-1).ToNodeAddr, NodeExpectations{
LAddr: containers.OptionalValue(path.Node(-1).ToNodeAddr),
Level: containers.OptionalValue(path.Node(-1).ToNodeLevel),
Generation: containers.OptionalValue(path.Node(-1).ToNodeGeneration),
Owner: checkOwner,
MinItem: containers.OptionalValue(path.Node(-1).ToKey),
MaxItem: containers.OptionalValue(path.Node(-1).ToMaxKey),
}, true
}
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