From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jan Blunck Subject: Re: [PATCH 00/32] VFS based Union Mount (V3) Date: Tue, 19 May 2009 12:29:39 +0200 Message-ID: <20090519102939.GK16526@bolzano.suse.de> References: <1242662968-11684-1-git-send-email-jblunck@suse.de> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, viro@zeniv.linux.org.uk, bharata@in.ibm.com, dwmw2@infradead.org, mszeredi@suse.cz, vaurora@redhat.com To: Miklos Szeredi Return-path: Received: from cantor2.suse.de ([195.135.220.15]:52495 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751520AbZESK3j (ORCPT ); Tue, 19 May 2009 06:29:39 -0400 Content-Disposition: inline In-Reply-To: Sender: linux-fsdevel-owner@vger.kernel.org List-ID: On Tue, May 19, Miklos Szeredi wrote: > > Major changes since last post: > > - Updated the whiteout patches: > > - DCACHE_WHITEOUT flag set on a negative dentry > > - uses filetype instead of reserved inode number on EXT2 > > - Copy-up directories during lookup > > - Implemented fallthru support for in-kernel readdir() as proposed by > > Valerie Aurora (Henson) > > Does this copy up directories persistently? If so, does this > implementation no longer supports union of all read-only branches? The directory in the topmost filesystem is created during lookup. The contents of the directory isn't copied up presistently at that point in time. Therefore you have an empty directory in the topmost filesystem after the lookup. This was necessary to get rid of the union_relookup_topmost() calls during create, mknod, mkdir etc. When readdir is called, the topmost directory is filed up with fallthru entries which are persistently stored. This is only necessary to get readdir right wrt POSIX. During lookup the fallthru dentry, which is in fact a special negative dentry, is ignored and therefore the lookup continues on the lower filesystem. Hope that clarifies your questions, Jan