MongoDb c# driver update multiple documents in one atomic operation-Collection of common programming errors

I want to ask you if the following code will be executed in one atomic operation. I’m using mongodb c# driver.

The input to the method is list of id of the objects I want to update.

public void Update(IEnumerable ids)
{
    var query = Query.Where(t => ids.Contains(t.Id));
    var update = Update.Set("Modified", DateTime.Now); //this is just example of update

    var options = new MongoUpdateOptions {Flags = UpdateFlags.Multi};

    Collection.Update(query, update, options);
}

I’m interesting about the case, when I have milions of documents to update. What will happen if there will be a fail (power or hardware problem) during this update? Will be the database in a consistent state?

thanks.