+int btrfs_write_and_wait_transaction(struct btrfs_trans_handle *trans,
+ struct btrfs_root *root)
+{
+ if (!trans || !trans->transaction) {
+ struct inode *btree_inode;
+ btree_inode = root->fs_info->btree_inode;
+ return filemap_write_and_wait(btree_inode->i_mapping);
+ }
+ return btrfs_write_and_wait_marked_extents(root,
+ &trans->transaction->dirty_pages);
+}
+
+/*
+ * this is used to update the root pointer in the tree of tree roots.
+ *
+ * But, in the case of the extent allocation tree, updating the root
+ * pointer may allocate blocks which may change the root of the extent
+ * allocation tree.
+ *
+ * So, this loops and repeats and makes sure the cowonly root didn't
+ * change while the root pointer was being updated in the metadata.
+ */