diff --git a/fs/btrfs/free-space-cache.c b/fs/btrfs/free-space-cache.c
index be45be6ec888..f3361ebfef4a 100644
--- a/fs/btrfs/free-space-cache.c
+++ b/fs/btrfs/free-space-cache.c
@@ -1721,6 +1721,8 @@ tree_search_offset(struct btrfs_free_space_ctl *ctl,
 	struct rb_node *n = ctl->free_space_offset.rb_node;
 	struct btrfs_free_space *entry = NULL, *prev = NULL;
 
+	lockdep_assert_held(&ctl->tree_lock);
+
 	/* find entry that is closest to the 'offset' */
 	while (n) {
 		entry = rb_entry(n, struct btrfs_free_space, offset_index);