Return-Path: linux-nfs-owner@vger.kernel.org Received: from mx1.netapp.com ([216.240.18.38]:51474 "EHLO mx1.netapp.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755480Ab3AWRhL convert rfc822-to-8bit (ORCPT ); Wed, 23 Jan 2013 12:37:11 -0500 From: "Myklebust, Trond" To: Alex Bligh CC: "linux-nfs@vger.kernel.org" , "ian.campbell@citrix.com" Subject: Re: Fatal crash with NFS, AIO & tcp retransmit Date: Wed, 23 Jan 2013 17:37:08 +0000 Message-ID: <4FA345DA4F4AE44899BD2B03EEEC2FA918331EF5@sacexcmbx05-prd.hq.netapp.com> References: <93D3AE9B4990994B2BCA75A9@Ximines.local> <4FA345DA4F4AE44899BD2B03EEEC2FA915C163B9@SACEXCMBX04-PRD.hq.netapp.com> <4FA345DA4F4AE44899BD2B03EEEC2FA915C17543@SACEXCMBX04-PRD.hq.netapp.com> <734E2E0455BD4515C657BA69@Ximines.local> <4FA345DA4F4AE44899BD2B03EEEC2FA915C1781E@SACEXCMBX04-PRD.hq.netapp.com> <4FA345DA4F4AE44899BD2B03EEEC2FA91832D572@sacexcmbx05-prd.hq.netapp.com> <5B18F9B0446E7F3CAA3BD81D@nimrod.local> In-Reply-To: <5B18F9B0446E7F3CAA3BD81D@nimrod.local> Content-Type: text/plain; charset=US-ASCII MIME-Version: 1.0 Sender: linux-nfs-owner@vger.kernel.org List-ID: On Wed, 2013-01-23 at 17:33 +0000, Alex Bligh wrote: > > --On 23 January 2013 15:34:42 +0000 "Myklebust, Trond" > wrote: > > > I've no idea if they do zero copy to the socket in these situations. If > > they do, then they probably have similar issues. The problem can be > > mitigated by breaking the connection on retransmission; we can't do that > > in NFS < NFSv4.1, since the duplicate replay cache is typically indexed > > to the port number (and port number reuse is difficult with TCP due to > > the existence of the TIME_WAIT state). > > If you break the connection, and the written data is now not available > to dom0 (as it's been mapped out), how would it ever get resent? IE > it's not going to be available to the RPC layer either. There are typically more than 1 outstanding RPC call at any one time. Breaking the connection would affect those other RPC calls. -- Trond Myklebust Linux NFS client maintainer NetApp Trond.Myklebust@netapp.com www.netapp.com