Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932358Ab3COUac (ORCPT ); Fri, 15 Mar 2013 16:30:32 -0400 Received: from zeniv.linux.org.uk ([195.92.253.2]:44983 "EHLO ZenIV.linux.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932313Ab3COUaa (ORCPT ); Fri, 15 Mar 2013 16:30:30 -0400 Date: Fri, 15 Mar 2013 20:30:18 +0000 From: Al Viro To: "J. R. Okajima" Cc: James Bottomley , Miklos Szeredi , Andrew Morton , torvalds@linux-foundation.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, hch@infradead.org, apw@canonical.com, nbd@openwrt.org, neilb@suse.de, jordipujolp@gmail.com, ezk@fsl.cs.sunysb.edu, dhowells@redhat.com, sedat.dilek@googlemail.com, mszeredi@suse.cz Subject: Re: [PATCH 0/9] overlay filesystem: request for inclusion (v17) Message-ID: <20130315203018.GZ21522@ZenIV.linux.org.uk> References: <20130313160854.54ac0491044371b4db214698@linux-foundation.org> <20130315012541.GU21522@ZenIV.linux.org.uk> <19058.1363320936@jrobl> <20130315044411.GW21522@ZenIV.linux.org.uk> <20079.1363324154@jrobl> <20130315051322.GX21522@ZenIV.linux.org.uk> <1363335318.2459.4.camel@dabdike> <20130315121220.GY21522@ZenIV.linux.org.uk> <29608.1363373838@jrobl> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <29608.1363373838@jrobl> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1321 Lines: 27 On Sat, Mar 16, 2013 at 03:57:18AM +0900, J. R. Okajima wrote: > > Al Viro: > > The trouble with such mechanisms is that they tend to end up depending on > > fairly non-trivial properties of underlying fs. Try aufs one on btrfs, > > see how soon you spot the problem. It's nice when a method turns out > > to be really redundant and implementable in uniform way via other methods > > present; see fh_to_dentry history for example of situation where it hadn't... > > Hmm, I could not see problem around aufs using btrfs as the upper RW > branch, tested on linux-3.9-rc2. > Would you describe more specifically? Sure - btrfs happens to have an interesting limit on the number of links to the same object located in one directory. The thing is, you are trying to retrofit a new primitive into many filesystems and do it in the same way. Doesn't work well... And yes, it is an independent primitive. What I really don't understand is WTF is so attractive about not having to touch individual filesystems; it's not particulary hard to do for any fs we might care about... -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/