From b6a7ab5f6c1fe993271242021c3ed4050733fdf2 Mon Sep 17 00:00:00 2001
From: Luke Shumaker <lukeshu@lukeshu.com>
Date: Mon, 29 Aug 2022 19:25:47 -0600
Subject: wip

---
 lib/btrfs/btrfstree/readnode.go | 27 ++++++++++++++++++++++-----
 lib/btrfs/io3_btree.go          | 17 +++++++++++------
 2 files changed, 33 insertions(+), 11 deletions(-)

(limited to 'lib/btrfs')

diff --git a/lib/btrfs/btrfstree/readnode.go b/lib/btrfs/btrfstree/readnode.go
index bb80d20..b1c34e4 100644
--- a/lib/btrfs/btrfstree/readnode.go
+++ b/lib/btrfs/btrfstree/readnode.go
@@ -13,14 +13,26 @@ import (
 	"git.lukeshu.com/btrfs-progs-ng/lib/diskio"
 )
 
+type NodeFile interface {
+	diskio.File[btrfsvol.LogicalAddr]
+	Superblock() (*Superblock, error)
+
+	// ParentTree, given a tree ID, returns that tree's parent
+	// tree, if it has one.
+	//
+	//  - non-zero, true : the parent tree ID
+	//
+	//  - 0, true : the tree does not have a parent
+	//
+	//  - any, false : the tree's parent information could not be
+	//    looked up
+	ParentTree(btrfsprim.ObjID) (btrfsprim.ObjID, bool)
+}
+
 // FSReadNode is a utility function to help with implementing the
 // 'NodeSource' interface.
 func FSReadNode(
-	fs interface {
-		diskio.File[btrfsvol.LogicalAddr]
-		Superblock() (*Superblock, error)
-		ParentTree(btrfsprim.ObjID) (btrfsprim.ObjID, bool)
-	},
+	fs NodeFile,
 	path TreePath,
 ) (*diskio.Ref[btrfsvol.LogicalAddr, Node], error) {
 	sb, err := fs.Superblock()
@@ -39,6 +51,11 @@ func FSReadNode(
 			var ok bool
 			exp, ok = fs.ParentTree(exp)
 			if !ok {
+				// Failed lookup up parent info; fail open.
+				return nil
+			}
+			if exp == 0 {
+				// End of the line.
 				return fmt.Errorf("expected owner in %v but claims to have owner=%v",
 					treeParents, owner)
 			}
diff --git a/lib/btrfs/io3_btree.go b/lib/btrfs/io3_btree.go
index 8455eee..26acc22 100644
--- a/lib/btrfs/io3_btree.go
+++ b/lib/btrfs/io3_btree.go
@@ -58,18 +58,23 @@ func (fs *FS) populateTreeUUIDs(ctx context.Context) {
 }
 
 func (fs *FS) ParentTree(tree btrfsprim.ObjID) (btrfsprim.ObjID, bool) {
-	ctx := context.TODO()
-	if tree < btrfsprim.FIRST_FREE_OBJECTID {
+	if tree < btrfsprim.FIRST_FREE_OBJECTID || tree > btrfsprim.LAST_FREE_OBJECTID {
+		// no parent
+		return 0, true
+	}
+	fs.populateTreeUUIDs(context.TODO())
+	parentUUID, ok := fs.cacheTreeParent[tree]
+	if !ok {
+		// could not look up parent info
 		return 0, false
 	}
-	fs.populateTreeUUIDs(ctx)
-	parentUUID := fs.cacheTreeParent[tree]
 	if parentUUID == (btrfsprim.UUID{}) {
-		return 0, false
+		// no parent
+		return 0, true
 	}
 	parentObjID, ok := fs.cacheUUID2ObjID[parentUUID]
 	if !ok {
-		dlog.Errorf(ctx, "dbg: could not resolve parentUUID=%v to an ObjID", parentUUID)
+		// could not look up parent info
 		return 0, false
 	}
 	return parentObjID, true
-- 
cgit v1.2.3-54-g00ecf