Merge branch 'lukeshu/tree-api-pt1-changes'

3 files changed, 27 insertions, 16 deletions

diff --git a/lib/btrfs/btrfstree/btree_forrest.go b/lib/btrfs/btrfstree/btree_forrest.go
index 8f8e2de..38a2721 100644
--- a/lib/btrfs/btrfstree/btree_forrest.go
+++ b/lib/btrfs/btrfstree/btree_forrest.go
@@ -21,6 +21,8 @@ type TreeRoot struct {
 	RootNode   btrfsvol.LogicalAddr
 	Level      uint8
 	Generation btrfsprim.Generation
+
+	RootInode btrfsprim.ObjID // only for subvolume trees
 }
 
 // LookupTreeRoot is a utility function to help with implementing the
@@ -59,7 +61,7 @@ func LookupTreeRoot(_ context.Context, fs TreeOperator, sb Superblock, treeID bt
 		rootItem, err := fs.TreeSearch(btrfsprim.ROOT_TREE_OBJECTID, SearchRootItem(treeID))
 		if err != nil {
 			if errors.Is(err, ErrNoItem) {
-				err = ErrNoTree
+				err = fmt.Errorf("%w: %s", ErrNoTree, err)
 			}
 			return nil, fmt.Errorf("tree %s: %w", treeID.Format(btrfsprim.ROOT_TREE_OBJECTID), err)
 		}
@@ -70,6 +72,7 @@ func LookupTreeRoot(_ context.Context, fs TreeOperator, sb Superblock, treeID bt
 				RootNode:   rootItemBody.ByteNr,
 				Level:      rootItemBody.Level,
 				Generation: rootItemBody.Generation,
+				RootInode:  rootItemBody.RootDirID,
 			}, nil
 		case *btrfsitem.Error:
 			return nil, fmt.Errorf("malformed ROOT_ITEM for tree %v: %w", treeID, rootItemBody.Err)
diff --git a/lib/btrfs/btrfstree/readnode.go b/lib/btrfs/btrfstree/readnode.go
index c2e3b0f..ac82c62 100644
--- a/lib/btrfs/btrfstree/readnode.go
+++ b/lib/btrfs/btrfstree/readnode.go
@@ -20,13 +20,13 @@ type NodeFile interface {
 	// ParentTree, given a tree ID, returns that tree's parent
 	// tree, if it has one.
 	//
-	//  - non-zero, true : the parent tree ID
+	//  - non-zero, ?, true : the parent tree ID
 	//
-	//  - 0, true : the tree does not have a parent
+	//  - 0, 0, true : the tree does not have a parent
 	//
-	//  - any, false : the tree's parent information could not be
+	//  - ?, ?, false : the tree's parent information could not be
 	//    looked up
-	ParentTree(btrfsprim.ObjID) (btrfsprim.ObjID, bool)
+	ParentTree(btrfsprim.ObjID) (btrfsprim.ObjID, btrfsprim.Generation, bool)
 }
 
 // FSReadNode is a utility function to help with implementing the
@@ -40,25 +40,33 @@ func FSReadNode(
 		return nil, fmt.Errorf("btrfs.FS.ReadNode: %w", err)
 	}
 
-	var treeParents []btrfsprim.ObjID
-	checkOwner := func(owner btrfsprim.ObjID) error {
-		exp := path.Node(-1).FromTree
+	checkOwner := func(owner btrfsprim.ObjID, gen btrfsprim.Generation) error {
+		var treeParents []btrfsprim.ObjID
+
+		tree := path.Node(-1).FromTree
 		for {
-			if owner == exp {
+			if owner == tree {
+				// OK!
 				return nil
 			}
-			treeParents = append(treeParents, exp)
-			var ok bool
-			exp, ok = fs.ParentTree(exp)
-			if !ok {
+
+			treeParents = append(treeParents, tree)
+			parent, parentGen, parentOK := fs.ParentTree(tree)
+			if !parentOK {
 				// Failed look up parent info; fail open.
 				return nil
 			}
-			if exp == 0 {
+
+			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
 		}
 	}
 
diff --git a/lib/btrfs/btrfstree/types_node.go b/lib/btrfs/btrfstree/types_node.go
index 622f23c..bfcbbf4 100644
--- a/lib/btrfs/btrfstree/types_node.go
+++ b/lib/btrfs/btrfstree/types_node.go
@@ -417,7 +417,7 @@ type NodeExpectations struct {
 	// Things knowable from the parent.
 	Level      containers.Optional[uint8]
 	Generation containers.Optional[btrfsprim.Generation]
-	Owner      func(btrfsprim.ObjID) error
+	Owner      func(btrfsprim.ObjID, btrfsprim.Generation) error
 	MinItem    containers.Optional[btrfsprim.Key]
 	// Things knowable from the structure of the tree.
 	MaxItem containers.Optional[btrfsprim.Key]
@@ -547,7 +547,7 @@ func (exp NodeExpectations) Check(node *Node) error {
 			exp.Generation.Val, node.Head.Generation))
 	}
 	if exp.Owner != nil {
-		if err := exp.Owner(node.Head.Owner); err != nil {
+		if err := exp.Owner(node.Head.Owner, node.Head.Generation); err != nil {
 			errs = append(errs, err)
 		}
 	}