Btrfs: improve error handling for btrfs_insert_dir_item callers

This allows us to gracefully continue if we aren't able to insert
directory items, both for normal files/dirs and snapshots.

Signed-off-by: Chris Mason <chris.mason@oracle.com>
diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index 6e0ee9b..cbeb2e3 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -4585,7 +4585,8 @@
 		ret = btrfs_insert_dir_item(trans, root, name, name_len,
 					    parent_inode, &key,
 					    btrfs_inode_type(inode), index);
-		BUG_ON(ret);
+		if (ret)
+			goto fail_dir_item;
 
 		btrfs_i_size_write(parent_inode, parent_inode->i_size +
 				   name_len * 2);
@@ -4593,6 +4594,23 @@
 		ret = btrfs_update_inode(trans, root, parent_inode);
 	}
 	return ret;
+
+fail_dir_item:
+	if (unlikely(ino == BTRFS_FIRST_FREE_OBJECTID)) {
+		u64 local_index;
+		int err;
+		err = btrfs_del_root_ref(trans, root->fs_info->tree_root,
+				 key.objectid, root->root_key.objectid,
+				 parent_ino, &local_index, name, name_len);
+
+	} else if (add_backref) {
+		u64 local_index;
+		int err;
+
+		err = btrfs_del_inode_ref(trans, root, name, name_len,
+					  ino, parent_ino, &local_index);
+	}
+	return ret;
 }
 
 static int btrfs_add_nondir(struct btrfs_trans_handle *trans,