From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-1.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 1EB7DC28CC0 for ; Thu, 30 May 2019 17:12:25 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id E0708218D3 for ; Thu, 30 May 2019 17:12:24 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727081AbfE3RMY (ORCPT ); Thu, 30 May 2019 13:12:24 -0400 Received: from p3plsmtpa06-05.prod.phx3.secureserver.net ([173.201.192.106]:44132 "EHLO p3plsmtpa06-05.prod.phx3.secureserver.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726280AbfE3RMY (ORCPT ); Thu, 30 May 2019 13:12:24 -0400 X-Greylist: delayed 438 seconds by postgrey-1.27 at vger.kernel.org; Thu, 30 May 2019 13:12:24 EDT Received: from [192.168.0.67] ([24.218.182.144]) by :SMTPAUTH: with ESMTPSA id WOUDh6DqsqJz9WOUDh6HVD; Thu, 30 May 2019 10:05:06 -0700 Subject: Re: [PATCH 0/9] Multiple network connections for a single NFS mount. To: NeilBrown , Olga Kornievskaia , Chuck Lever , Schumaker Anna , Trond Myklebust Cc: linux-nfs@vger.kernel.org References: <155917564898.3988.6096672032831115016.stgit@noble.brown> From: Tom Talpey Message-ID: <1df23ebc-ffe5-1a57-c40a-d5e9a45c8498@talpey.com> Date: Thu, 30 May 2019 13:05:04 -0400 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:60.0) Gecko/20100101 Thunderbird/60.7.0 MIME-Version: 1.0 In-Reply-To: <155917564898.3988.6096672032831115016.stgit@noble.brown> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-CMAE-Envelope: MS4wfHotrCDW8LfWFHbzjXUttE/chEOfBdF179JzpT5kNoL5haycCKZLwA7PwMgE2ujtqgW/OFklXAWa/QbL8y5XogtX9afl8HevkPaPVbyuwVKhCNb3JjZ+ ngwFuCM5EMCI6HHwDV87k8UxibJR24bb48hn4bMw+8vc3wTcCrQ59np6McMMja8Cw4UmZ+oqMtpWoMFSq4ezVaQasi2i3uBCnlCPULLc9RLQJHqevgt0d7WD S2f9sLRDOUG/vR409Mj+kpp/lCdjAEgk5dCre6bER0UELs/K+K+v+I8qjwrV/kreDB+Lvln8a1MSbArF5WVpgt/+eTX2CfFGr4EGHc2siGw= Sender: linux-nfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-nfs@vger.kernel.org On 5/29/2019 8:41 PM, NeilBrown wrote: > I've also re-arrange the patches a bit, merged two, and remove the > restriction to TCP and NFSV4.x,x>=1. Discussions seemed to suggest > these restrictions were not needed, I can see no need. I believe the need is for the correctness of retries. Because NFSv2, NFSv3 and NFSv4.0 have no exactly-once semantics of their own, server duplicate request caches are important (although often imperfect). These caches use client XID's, source ports and addresses, sometimes in addition to other methods, to detect retry. Existing clients are careful to reconnect with the same source port, to ensure this. And existing servers won't change. Multiple connections will result in multiple source ports, and possibly multiple source addresses, meaning retried client requests may be accepted as new, rather than having any chance of being recognized as retries. NFSv4.1+ don't have this issue, but removing the restrictions would seem to break the downlevel mounts. Tom.