From mboxrd@z Thu Jan 1 00:00:00 1970 From: Valerie Aurora Subject: Re: [PATCH 0/5] hybrid union filesystem prototype Date: Mon, 30 Aug 2010 14:38:43 -0400 Message-ID: <20100830183843.GB2444@shell> References: <20100826183340.027591901@szeredi.hu> <20100827170551.19616048@notabene> <20100827213502.31af4a4c@notabene> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Miklos Szeredi , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, viro@zeniv.linux.org.uk, jblunck@suse.de, hch@infradead.org To: Neil Brown Return-path: Content-Disposition: inline In-Reply-To: <20100827213502.31af4a4c@notabene> Sender: linux-kernel-owner@vger.kernel.org List-Id: linux-fsdevel.vger.kernel.org On Fri, Aug 27, 2010 at 09:35:02PM +1000, Neil Brown wrote: > On Fri, 27 Aug 2010 10:47:39 +0200 > Miklos Szeredi wrote: > > > Changes to underlying filesystems > > > --------------------------------- > > > > > > > For now I refuse to even think about what happens in this case. > > > > The easiest way out of this mess might simply be to enforce exclusive > > modification to the underlying filesystems on a local level, same as > > the union mount strategy. For NFS and other remote filesystems we > > either > > > > a) add some way to enforce it, > > b) live with the consequences if not enforced on the system level, or > > c) disallow them to be part of the union. > > > > I actually think that your approach can work quite will with either the > upper or lower changing independently. Certainly it can produce some odd > situations, but even NFS can do that (though maybe not quite so odd). I'm very curious about your thoughts on how to handle the lower layer changing. Al Viro's comments: http://lkml.indiana.edu/hypermail/linux/kernel/0802.0/0839.html Do you see something we're missing? -VAL