From: "J. Bruce Fields" Subject: Re: regressions due to 64-bit ext4 directory cookies Date: Wed, 13 Feb 2013 16:33:46 -0500 Message-ID: <20130213213346.GQ14195@fieldses.org> References: <20130212202841.GC10267@fieldses.org> <20130213040003.GB2614@thunk.org> <20130213133131.GE14195@fieldses.org> <20130213151455.GB17431@thunk.org> <20130213151953.GJ14195@fieldses.org> <20130213153654.GC17431@thunk.org> <20130213162059.GL14195@fieldses.org> <4FA345DA4F4AE44899BD2B03EEEC2FA91F3D625D@sacexcmbx05-prd.hq.netapp.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Theodore Ts'o , "linux-ext4@vger.kernel.org" , "sandeen@redhat.com" , Bernd Schubert , "gluster-devel@nongnu.org" , "linux-nfs@vger.kernel.org" To: "Myklebust, Trond" Return-path: Received: from fieldses.org ([174.143.236.118]:35765 "EHLO fieldses.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751861Ab3BMVdy (ORCPT ); Wed, 13 Feb 2013 16:33:54 -0500 Content-Disposition: inline In-Reply-To: <4FA345DA4F4AE44899BD2B03EEEC2FA91F3D625D@sacexcmbx05-prd.hq.netapp.com> Sender: linux-ext4-owner@vger.kernel.org List-ID: On Wed, Feb 13, 2013 at 04:43:05PM +0000, Myklebust, Trond wrote: > On Wed, 2013-02-13 at 11:20 -0500, J. Bruce Fields wrote: > > Oops, probably should have cc'd linux-nfs. > > > > On Wed, Feb 13, 2013 at 10:36:54AM -0500, Theodore Ts'o wrote: > > > The other thing that I'd note is that the readdir cookie has been > > > 64-bit since NFSv3, which was released in June ***1995***. And the > > > explicit, stated purpose of making it be a 64-bit value (as stated in > > > RFC 1813) was to reduce interoperability problems. If that were the > > > case, are you telling me that Sun (who has traditionally been pretty > > > good worrying about interoperability concerns, and in fact employed > > > the editors of RFC 1813) didn't get this right? This seems > > > quite.... surprising to me. > > > > > > I thought this was the whole point of the various NFS interoperability > > > testing done at Connectathon, for which Sun was a major sponsor?!? No > > > one noticed?!? > > > > Beats me. But it's not necessarily easy to replace clients running > > legacy applications, so we're stuck working with the clients we have.... > > > > The linux client does remap the server-provided cookies to small > > integers, I believe exactly because older applications had trouble with > > servers returning "large" cookies. So presumably ext4-exporting-Linux > > servers aren't the first to do this. > > > > I don't know which client versions are affected--Connectathon's next > > week and I'll talk to people and make sure there's an ext4 export with > > this turned on to test against. > > Actually, one of the main reasons for the Linux client not exporting raw > readdir cookies is because the glibc-2 folks in their infinite wisdom > declared that telldir()/seekdir() use an off_t. They then went yet one > further and decided to declare negative offsets to be illegal so that > they could use the negative values internally in their syscall wrappers. > > The POSIX definition has none of the above rubbish > (http://pubs.opengroup.org/onlinepubs/009695399/functions/telldir.html) > and so glibc brilliantly saddled Linux with a crippled readdir > implementation that is _not_ POSIX compatible. > > No, I'm not at all bitter... Oh, right, I knew I'd forgotten part of the story.... But then you must have actually been testing against servers that were using that 32nd bit? I think ext4 actually only uses 31 bits even in the 32-bit case. And for a server that was literally using an offset inside a directory file, that would be a colossal directory. So I'm wondering how you ran across it. Partly just pure curiosity. --b.