From mboxrd@z Thu Jan 1 00:00:00 1970 From: Valerie Aurora Subject: Re: [PATCH 0/5] hybrid union filesystem prototype Date: Tue, 31 Aug 2010 15:18:46 -0400 Message-ID: <20100831191846.GA5759@shell> References: <20100826183340.027591901@szeredi.hu> <20100827170551.19616048@notabene> <20100827213502.31af4a4c@notabene> <20100829144207.4fbf2713@notabene> <20100830214027.77e197f5@notabene> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Neil Brown , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, viro@zeniv.linux.org.uk, jblunck@suse.de, hch@infradead.org To: Miklos Szeredi , Trond Myklebust , "J. Bruce Fields" Return-path: Content-Disposition: inline In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org List-Id: linux-fsdevel.vger.kernel.org On Mon, Aug 30, 2010 at 02:20:47PM +0200, Miklos Szeredi wrote: > On Mon, 30 Aug 2010, Neil Brown wrote: > > > Val has been following that approach and asking if it is possible to make an > > NFS filesystem really-truly read-only. i.e. no changes. > > I don't believe it is. > > Perhaps it doesn't matter. The nasty cases can be prevented by just > disallowing local modification. For the rest NFS will return ESTALE: > "though luck, why didn't you follow the rules?" I agree: Ask the server to keep it read-only, but also detect if it lied to prevent kernel bugs on the client. Is detecting ESTALE and failing the mount sufficient to detect all cases of a cached directory being altered? I keep trying to trap an NFS developer and beat the answer out of him but they usually get hung up on the impossibility of 100% enforcement of the read-only server option. (Agreed, impossible, just give the sysadmin a mount option so that it doesn't happen accidentally.) -VAL