From ee2564cc3164e2c235b3d617a1a4fed2f9d9efc6 Mon Sep 17 00:00:00 2001
From: Luke Shumaker <lukeshu@lukeshu.com>
Date: Fri, 7 Apr 2023 15:30:46 -0600
Subject: btrfsutil.RebuiltForrest, rebuildtrees: Be more permissive of broken
 UUID_TREEs

---
 lib/btrfsutil/rebuilt_callbacks.go | 42 +++++++++++++++++++++++++++++++++++++-
 1 file changed, 41 insertions(+), 1 deletion(-)

(limited to 'lib/btrfsutil')

diff --git a/lib/btrfsutil/rebuilt_callbacks.go b/lib/btrfsutil/rebuilt_callbacks.go
index b5fbc91..8d96c41 100644
--- a/lib/btrfsutil/rebuilt_callbacks.go
+++ b/lib/btrfsutil/rebuilt_callbacks.go
@@ -57,11 +57,17 @@ func (cb noopRebuiltForrestCallbacks) LookupRoot(ctx context.Context, tree btrfs
 func (cb noopRebuiltForrestCallbacks) LookupUUID(ctx context.Context, uuid btrfsprim.UUID) (id btrfsprim.ObjID, err error) {
 	uuidTree, err := cb.forrest.ForrestLookup(ctx, btrfsprim.UUID_TREE_OBJECTID)
 	if err != nil {
+		if id, ok := cb.slowLookupUUID(ctx, uuid); ok {
+			return id, nil
+		}
 		return 0, err
 	}
 	tgt := btrfsitem.UUIDToKey(uuid)
 	item, err := uuidTree.TreeLookup(ctx, tgt)
 	if err != nil {
+		if id, ok := cb.slowLookupUUID(ctx, uuid); ok {
+			return id, nil
+		}
 		return 0, err
 	}
 	defer item.Body.Free()
@@ -69,10 +75,44 @@ func (cb noopRebuiltForrestCallbacks) LookupUUID(ctx context.Context, uuid btrfs
 	case *btrfsitem.UUIDMap:
 		return itemBody.ObjID, nil
 	case *btrfsitem.Error:
-		return 0, itemBody.Err
+		if id, ok := cb.slowLookupUUID(ctx, uuid); ok {
+			return id, nil
+		}
+		return 0, err
 	default:
 		// This is a panic because the item decoder should not emit UUID_SUBVOL items as anything but
 		// btrfsitem.UUIDMap or btrfsitem.Error without this code also being updated.
 		panic(fmt.Errorf("should not happen: UUID_SUBVOL item has unexpected type: %T", itemBody))
 	}
 }
+
+func (cb noopRebuiltForrestCallbacks) slowLookupUUID(ctx context.Context, uuid btrfsprim.UUID) (id btrfsprim.ObjID, ok bool) {
+	rootTree, err := cb.forrest.ForrestLookup(ctx, btrfsprim.ROOT_TREE_OBJECTID)
+	if err != nil {
+		return 0, false
+	}
+	var ret btrfsprim.ObjID
+	_ = rootTree.TreeRange(ctx, func(item btrfstree.Item) bool {
+		if item.Key.ItemType != btrfsprim.ROOT_ITEM_KEY {
+			return true
+		}
+		switch itemBody := item.Body.(type) {
+		case *btrfsitem.Root:
+			if itemBody.UUID == uuid {
+				ret = item.Key.ObjectID
+				return false
+			}
+		case *btrfsitem.Error:
+			// do nothing
+		default:
+			// This is a panic because the item decoder should not emit ROOT_ITEM items as anything but
+			// btrfsitem.Root or btrfsitem.Error without this code also being updated.
+			panic(fmt.Errorf("should not happen: ROOT_ITEM item has unexpected type: %T", itemBody))
+		}
+		return true
+	})
+	if ret == 0 {
+		return 0, false
+	}
+	return ret, true
+}
-- 
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