From: "J. Bruce Fields" Subject: Re: regressions due to 64-bit ext4 directory cookies Date: Wed, 13 Feb 2013 08:40:33 -0500 Message-ID: <20130213134033.GF14195@fieldses.org> References: <20130212202841.GC10267@fieldses.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: linux-ext4@vger.kernel.org, sandeen@redhat.com, Theodore Ts'o , Bernd Schubert , gluster-devel@nongnu.org To: Andreas Dilger Return-path: Received: from fieldses.org ([174.143.236.118]:43191 "EHLO fieldses.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755759Ab3BMNkh (ORCPT ); Wed, 13 Feb 2013 08:40:37 -0500 Content-Disposition: inline In-Reply-To: Sender: linux-ext4-owner@vger.kernel.org List-ID: On Tue, Feb 12, 2013 at 10:56:36PM -0800, Andreas Dilger wrote: > On 2013-02-12, at 12:28 PM, J. Bruce Fields wrote: > > 06effdbb49af5f6c "nfsd: vfs_llseek() with 32 or 64 bit offsets (hashes)" > > and previous patches solved problems with hash collisions in large > > directories by using 64- instead of 32- bit directory hashes in some > > cases. But it caused problems for users who assume directory offsets > > are "small". Two cases we've run across: > > > > - older NFS clients: 64-bit cookies cause applications on > > many older clients to fail. > > - gluster: gluster assumed that it could take the top bits of > > the offset for its own use. > > > > In both cases we could argue we're in the right: the nfs protocol > > defines cookies to be 64 bits, so clients should be prepared to handle them (remapping to smaller integers if necessary to placate > > applications using older system interfaces). > > There appears to already be support for handling this for NFSv2 > clients, so it should be possible to have an NFS server mount > option to set this for all clients: > > /* NFSv2 only supports 32 bit cookies */ > if (rqstp->rq_vers > 2) > may_flags |= NFSD_MAY_64BIT_COOKIE; > > Alternately, this might be detected on a per-client basis by > whitelist or blacklist if there is some way for the server to > identify the client? No, there isn't. --b.