diff --git a/fs/btrfs/free-space-cache.c b/fs/btrfs/free-space-cache.c
index 7f90c2bf9d5f..4ba0aedc878b 100644
--- a/fs/btrfs/free-space-cache.c
+++ b/fs/btrfs/free-space-cache.c
@@ -2458,6 +2458,7 @@ void btrfs_dump_free_space(struct btrfs_block_group_cache *block_group,
 	struct rb_node *n;
 	int count = 0;
 
+	spin_lock(&ctl->tree_lock);
 	for (n = rb_first(&ctl->free_space_offset); n; n = rb_next(n)) {
 		info = rb_entry(n, struct btrfs_free_space, offset_index);
 		if (info->bytes >= bytes && !block_group->ro)
@@ -2466,6 +2467,7 @@ void btrfs_dump_free_space(struct btrfs_block_group_cache *block_group,
 			   info->offset, info->bytes,
 		       (info->bitmap) ? "yes" : "no");
 	}
+	spin_unlock(&ctl->tree_lock);
 	btrfs_info(fs_info, "block group has cluster?: %s",
 	       list_empty(&block_group->cluster_list) ? "no" : "yes");
 	btrfs_info(fs_info,