Merge branch 'lukeshu/node-cache'

1 files changed, 11 insertions, 13 deletions

diff --git a/lib/btrfs/btrfstree/readnode.go b/lib/btrfs/btrfstree/readnode.go
index ac82c62..a4ccf10 100644
--- a/lib/btrfs/btrfstree/readnode.go
+++ b/lib/btrfs/btrfstree/readnode.go
@@ -14,8 +14,7 @@ import (
 )
 
 type NodeFile interface {
-	diskio.File[btrfsvol.LogicalAddr]
-	Superblock() (*Superblock, error)
+	diskio.ReaderAt[btrfsvol.LogicalAddr]
 
 	// ParentTree, given a tree ID, returns that tree's parent
 	// tree, if it has one.
@@ -29,15 +28,14 @@ type NodeFile interface {
 	ParentTree(btrfsprim.ObjID) (btrfsprim.ObjID, btrfsprim.Generation, bool)
 }
 
-// FSReadNode is a utility function to help with implementing the
-// 'NodeSource' interface.
-func FSReadNode(
-	fs NodeFile,
-	path Path,
-) (*Node, error) {
-	sb, err := fs.Superblock()
-	if err != nil {
-		return nil, fmt.Errorf("btrfs.FS.ReadNode: %w", err)
+// 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 {
@@ -70,12 +68,12 @@ func FSReadNode(
 		}
 	}
 
-	return ReadNode[btrfsvol.LogicalAddr](fs, *sb, path.Node(-1).ToNodeAddr, NodeExpectations{
+	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
 }