From d0b7bc25341c936e96a64a540824f77ed79878ce Mon Sep 17 00:00:00 2001
From: Luke Shumaker <lukeshu@lukeshu.com>
Date: Thu, 30 Mar 2023 00:53:34 -0600
Subject: btrfstree: Move Path.NodeExpectations from readnode.go to path.go

---
 lib/btrfs/btrfstree/path.go | 51 +++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 51 insertions(+)

(limited to 'lib/btrfs/btrfstree/path.go')

diff --git a/lib/btrfs/btrfstree/path.go b/lib/btrfs/btrfstree/path.go
index c07d8a0..1335b76 100644
--- a/lib/btrfs/btrfstree/path.go
+++ b/lib/btrfs/btrfstree/path.go
@@ -11,6 +11,7 @@ import (
 
 	"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"
 )
 
 // Path is a path from the superblock (i.e. the root of the btrfs
@@ -123,6 +124,56 @@ func (path Path) DeepCopy() Path {
 	return append(Path(nil), path...)
 }
 
+// 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
+}
+
 func (path Path) Parent() Path {
 	return path[:len(path)-1]
 }
-- 
cgit v1.2.3-54-g00ecf