Return-Path: Received: from aserp1040.oracle.com ([141.146.126.69]:19497 "EHLO aserp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S966388AbcDLSIy (ORCPT ); Tue, 12 Apr 2016 14:08:54 -0400 Content-Type: text/plain; charset=us-ascii Mime-Version: 1.0 (Mac OS X Mail 9.3 \(3124\)) Subject: Re: [PATCH v1 05/18] xprtrdma: Avoid using Write list for small NFS READ requests From: Chuck Lever In-Reply-To: <20160412170121.GA2052@infradead.org> Date: Tue, 12 Apr 2016 14:08:25 -0400 Cc: Steve Wise , linux-rdma , Linux NFS Mailing List Message-Id: <609A9E12-B1A8-4662-B64B-67CB46333D14@oracle.com> References: <20160411200323.20531.8893.stgit@manet.1015granger.net> <20160411201050.20531.53651.stgit@manet.1015granger.net> <033901d19431$b3725d20$1a571760$@opengridcomputing.com> <65CBC59F-3005-44FE-8C70-9DDBC8507C9E@oracle.com> <20160412141533.GA16218@infradead.org> <06326E24-7170-4D09-A841-08ED31D143FF@oracle.com> <20160412170121.GA2052@infradead.org> To: Christoph Hellwig Sender: linux-nfs-owner@vger.kernel.org List-ID: > On Apr 12, 2016, at 1:01 PM, Christoph Hellwig wrote: > > On Tue, Apr 12, 2016 at 10:49:24AM -0400, Chuck Lever wrote: >>>> No, pre-4.2 Linux servers have a bug that can be fixed by >>>> applying the above commit, which shouldn't be difficult to >>>> backport. >>>> >>>> Clients have always been allowed to send NFS READ this way. >>> >>> But the clients might be out in a the wild. I think we'll need at >>> least a mount option to work around them. >> >> Huh? >> >> I'm talking about non-Linux clients. RFC 5666 allows >> this behavior, it always has. The Linux server before >> 9d11b51ce7c1 is broken, full stop. > > You are deliverately breaking exsisting and fairly recent clients. How am I breaking existing clients? Before 4.7, our client works with a broken Linux NFS server and it works with a fixed one. _New_ clients won't work with broken servers. > I see why we want to do this, but there needs to be an options > that things keep working. The idea of upgrading your client from > 4.6 to 4.7 and NFS simply not working anymore with the developer > knowing it and not providing a workaround is simply not an option. I don't understand why this approach was reasonable in the past, but is now suddenly not workable. We have a workaround: Use NFS/TCP on IPoIB. -- Chuck Lever