diff --git a/fs/btrfs/free-space-cache.c b/fs/btrfs/free-space-cache.c
index 1aa897dd9ce3e4..6c0161284a9e83 100644
--- a/fs/btrfs/free-space-cache.c
+++ b/fs/btrfs/free-space-cache.c
@@ -2469,6 +2469,7 @@ 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)
@@ -2478,6 +2479,7 @@ 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(block_group->fs_info, "block group has cluster?: %s",
 	       list_empty(&block_group->cluster_list) ? "no" : "yes");
 	btrfs_info(block_group->fs_info,