From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tejun Heo Subject: Re: [PATCH 2/4] sysfs: Implement sysfs manged shadow directory support. Date: Mon, 30 Jul 2007 16:09:06 +0900 Message-ID: <46AD8E92.7080002@suse.de> References: <1182446577.8138.29.camel@localhost> <20070621211637.GB10583@suse.de> <20070622001328.GA14113@suse.de> <20070625212339.GA13398@kroah.com> <46A3B449.3090409@gmail.com> <20070722202508.GA18018@suse.de> <46A425F9.1030008@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <46A425F9.1030008-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: containers-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org Errors-To: containers-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org To: "Eric W. Biederman" Cc: Linux Containers , Greg KH , Greg KH , Dave Hansen List-Id: containers.vger.kernel.org Hello, Eric. Tejun Heo wrote: > Eric W. Biederman wrote: >> Further while there are a few little nits I think mostly Tejun is >> mostly objecting to the fundamental complexity of the problem rather >> then to things that can be fixed by a cleaner implementation. > > Oh well, I don't think so but I might be wrong. And I'm wrong. Mine didn't turn out to be much cleaner than yours. What I did was (still broken)... * No shadower/shadowee. Each dentry is tagged. * dentries of tagged sd's are taken out of dcache and always go through ->lookup() where the correct sd is looked up considering the current tag. Tagging and adding new entries could be done rather cleanly but shooting down existing dentries on rename/move turned out to be a mess. Things will be much simpler if no sysfs dentry is hashed on dcache and always go through ->lookup() but that will hurt big machines. The basic problem here is that dcache layer doesn't allow different views and sysfs shadow is trying to work behind its back. I don't think this is a viable approach. Both implementations bend too many rules and are too fragile. It will be a genuine pain in the ass to maintain. Sorry that I can't come up with an alternative but NACK. -- tejun