From: David Howells <dhowells@redhat.com>
Subject: Unionmount fallthru directory entries
Date: Wed, 11 May 2011 18:00:19 +0100
Message-ID: <30230.1305133219@redhat.com>
Cc: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
	dhowells@redhat.com
To: Valerie Aurora <valerie.aurora@gmail.com>, viro@zeniv.linux.org.uk
Return-path: <linux-kernel-owner@vger.kernel.org>
Sender: linux-kernel-owner@vger.kernel.org
List-Id: linux-fsdevel.vger.kernel.org


What are unionmount fallthru directory entries for and why are they needed?

I'm guess that what they do is indicate that the dirent in question must be
looked up in the corresponding directory on the underlying fs.

As to why they are needed, am I right in thinking that unionmount caches a
copy of all the lower directory's entries in the upper directory with fallthru
markers set on the first call to readdir?

David