rebuildnodes: Rework to be clear about what went wrong when reading

3 files changed, 14 insertions, 28 deletions

diff --git a/lib/btrfsprogs/btrfsinspect/rebuildnodes/btrees/tree.go b/lib/btrfsprogs/btrfsinspect/rebuildnodes/btrees/tree.go
index c9d0fa4..f870121 100644
--- a/lib/btrfsprogs/btrfsinspect/rebuildnodes/btrees/tree.go
+++ b/lib/btrfsprogs/btrfsinspect/rebuildnodes/btrees/tree.go
@@ -329,10 +329,10 @@ func (tree *RebuiltTree) COWDistance(parentID btrfsprim.ObjID) (dist int, ok boo
 }
 
 // ReadItem reads an item from a tree.
-func (tree *RebuiltTree) ReadItem(ctx context.Context, key btrfsprim.Key) (item btrfsitem.Item, ok bool) {
+func (tree *RebuiltTree) ReadItem(ctx context.Context, key btrfsprim.Key) btrfsitem.Item {
 	ptr, ok := tree.Items(ctx).Load(key)
 	if !ok {
-		return nil, false
+		panic(fmt.Errorf("should not happen: btrees.RebuiltTree.ReadItem called for not-included key: %v", key))
 	}
 	return tree.forrest.keyIO.ReadItem(ctx, ptr)
 }
diff --git a/lib/btrfsprogs/btrfsinspect/rebuildnodes/keyio/keyio.go b/lib/btrfsprogs/btrfsinspect/rebuildnodes/keyio/keyio.go
index b4ab645..9e3b144 100644
--- a/lib/btrfsprogs/btrfsinspect/rebuildnodes/keyio/keyio.go
+++ b/lib/btrfsprogs/btrfsinspect/rebuildnodes/keyio/keyio.go
@@ -152,13 +152,17 @@ func (o *Handle) readNode(ctx context.Context, laddr btrfsvol.LogicalAddr) *disk
 	return ref
 }
 
-func (o *Handle) ReadItem(ctx context.Context, ptr ItemPtr) (item btrfsitem.Item, ok bool) {
-	if o.graph.Nodes[ptr.Node].Level != 0 || ptr.Idx < 0 {
-		return nil, false
+func (o *Handle) ReadItem(ctx context.Context, ptr ItemPtr) btrfsitem.Item {
+	if o.graph.Nodes[ptr.Node].Level != 0 {
+		panic(fmt.Errorf("should not happen: keyio.Handle.ReadItem called for non-leaf node@%v", ptr.Node))
+	}
+	if ptr.Idx < 0 {
+		panic(fmt.Errorf("should not happen: keyio.Handle.ReadItem called for negative item index: %v", ptr.Idx))
 	}
 	items := o.readNode(ctx, ptr.Node).Data.BodyLeaf
 	if ptr.Idx >= len(items) {
-		return nil, false
+		panic(fmt.Errorf("should not happen: keyio.Handle.ReadItem called for out-of-bounds item index: index=%v len=%v",
+			ptr.Idx, len(items)))
 	}
-	return items[ptr.Idx].Body, true
+	return items[ptr.Idx].Body
 }
diff --git a/lib/btrfsprogs/btrfsinspect/rebuildnodes/rebuild.go b/lib/btrfsprogs/btrfsinspect/rebuildnodes/rebuild.go
index 624441f..d11ca58 100644
--- a/lib/btrfsprogs/btrfsinspect/rebuildnodes/rebuild.go
+++ b/lib/btrfsprogs/btrfsinspect/rebuildnodes/rebuild.go
@@ -91,12 +91,6 @@ func NewRebuilder(ctx context.Context, fs *btrfs.FS, nodeScanResults btrfsinspec
 	return o, nil
 }
 
-func (o *rebuilder) ioErr(ctx context.Context, err error) {
-	err = fmt.Errorf("should not happen: i/o error: %w", err)
-	dlog.Error(ctx, err)
-	panic(err)
-}
-
 func (o *rebuilder) ListRoots() map[btrfsprim.ObjID]containers.Set[btrfsvol.LogicalAddr] {
 	return o.rebuilt.ListRoots()
 }
@@ -174,13 +168,9 @@ func (o *rebuilder) Rebuild(_ctx context.Context) error {
 						return err
 					}
 					itemCtx := dlog.WithField(stepCtx, "btrfsinspect.rebuild-nodes.rebuild.process.item", key)
-					itemBody, ok := o.rebuilt.Tree(itemCtx, key.TreeID).ReadItem(itemCtx, key.Key)
-					if !ok {
-						o.ioErr(itemCtx, fmt.Errorf("could not read previously read item: %v", key))
-					}
 					itemChan <- keyAndBody{
 						keyAndTree: key,
-						Body:       itemBody,
+						Body:       o.rebuilt.Tree(itemCtx, key.TreeID).ReadItem(itemCtx, key.Key),
 					}
 				}
 				return nil
@@ -285,11 +275,7 @@ func (o *rebuilder) cbLookupRoot(ctx context.Context, tree btrfsprim.ObjID) (off
 		o.enqueueRetry()
 		return 0, btrfsitem.Root{}, false
 	}
-	itemBody, ok := o.rebuilt.Tree(ctx, key.TreeID).ReadItem(ctx, key.Key)
-	if !ok {
-		o.ioErr(ctx, fmt.Errorf("could not read previously read item: %v", key))
-	}
-	switch itemBody := itemBody.(type) {
+	switch itemBody := o.rebuilt.Tree(ctx, key.TreeID).ReadItem(ctx, key.Key).(type) {
 	case *btrfsitem.Root:
 		return btrfsprim.Generation(key.Offset), *itemBody, true
 	case *btrfsitem.Error:
@@ -310,11 +296,7 @@ func (o *rebuilder) cbLookupUUID(ctx context.Context, uuid btrfsprim.UUID) (id b
 		o.enqueueRetry()
 		return 0, false
 	}
-	itemBody, ok := o.rebuilt.Tree(ctx, key.TreeID).ReadItem(ctx, key.Key)
-	if !ok {
-		o.ioErr(ctx, fmt.Errorf("could not read previously read item: %v", key))
-	}
-	switch itemBody := itemBody.(type) {
+	switch itemBody := o.rebuilt.Tree(ctx, key.TreeID).ReadItem(ctx, key.Key).(type) {
 	case *btrfsitem.UUIDMap:
 		return itemBody.ObjID, true
 	case *btrfsitem.Error: