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=-0.9 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,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 CFF7DC43381 for ; Fri, 22 Feb 2019 14:47:10 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 9D0F3206A3 for ; Fri, 22 Feb 2019 14:47:10 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="fzlhDPLa" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726798AbfBVOrK (ORCPT ); Fri, 22 Feb 2019 09:47:10 -0500 Received: from mail-ua1-f66.google.com ([209.85.222.66]:46446 "EHLO mail-ua1-f66.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725978AbfBVOrJ (ORCPT ); Fri, 22 Feb 2019 09:47:09 -0500 Received: by mail-ua1-f66.google.com with SMTP id j8so2113384uae.13 for ; Fri, 22 Feb 2019 06:47:09 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=yUfhcpmpMfdg9+8PJndXjFHOmyPOT5v3mdQLXDj7FMo=; b=fzlhDPLa4fXkV1qtmEdbMmlTYedrS4Xin0IB8oCLNnN48DsMREUVAIiypiGIgWAike x89nTW+9+oK1kytfelOfAFV2SKz+/m+xma6m/DBRbU4u8rieuGaj7sZVGqt7zlsJKWF2 dY/1Tk2DXEHvpSqdWYwBnFt4qHRObEgziT9DrMQXwF6pM2VujbXCZPzEDEgRWXss1hc5 sXj9SMiZTxsRGqa4/VGD3frWnCW04UFwbXR+xN09FC6iq579Yb+kFZF0yaBux28gIv6w NVQ/ayS519fGb5DiDEGTvrhaTGMgAgDeB8PuX65U/yY93sL8qnN06CykOTRfr3JPaPgv uCCA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=yUfhcpmpMfdg9+8PJndXjFHOmyPOT5v3mdQLXDj7FMo=; b=Lx/X14aXcdyT6ZYbz7Lsi33F/6AfK8EowHuHxc6rjU+1Ry5nV63wWnNZ/OMRip+4Pu kClp3Hb2KB/7UkI+T8MS9BqlezvxQdDnJAu+0I4nDIY15dIKNf/nxS3ywtlKIP2g0NKK xsKAobSTuzakeEAX3KO8rpm6m4eBbFrYVqQGIENmjVRoIavd7xSBKdnY7MiD5fFPvJP9 jxa3o53erdEzVZEisbdr4tw5WlM+PYmGK3WV3EE/1uPgk7DAaL8uFSYFeBqqam+BHoWb FDLK954MQzh6F8bs5yhJqLqsAyXCTcuYT+QyrQA6DMHSQY1squQYQxcXpqqBIuQNQ9xg XNAA== X-Gm-Message-State: AHQUAubvQpdVwipIIFUOPTPQznp/S/Ymh80ZBl8Ly9oa9Bz5zrDDf9eS fi1+l8nlelkedGaCSEUiJ6MV1GwPw+CwIsB7KwfZ3w== X-Google-Smtp-Source: AHgI3Ib346KBk4J3kqT9O0Xmlz0jk4EF0K0WmhWnMIc0cntLUB4U0FM5xG5DP1azyGNJMh06GOcR9VimJE9CKjd1Zrc= X-Received: by 2002:a05:6102:150:: with SMTP id a16mr2365590vsr.134.1550846828568; Fri, 22 Feb 2019 06:47:08 -0800 (PST) MIME-Version: 1.0 References: <20190220145650.21566-1-olga.kornievskaia@gmail.com> <1550837576.6456.3.camel@redhat.com> In-Reply-To: From: Olga Kornievskaia Date: Fri, 22 Feb 2019 09:46:57 -0500 Message-ID: Subject: Re: [PATCH 1/1] SUNRPC: fix handling of half-closed connection To: Trond Myklebust Cc: "anna.schumaker@netapp.com" , "dwysocha@redhat.com" , "linux-nfs@vger.kernel.org" Content-Type: text/plain; charset="UTF-8" Sender: linux-nfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-nfs@vger.kernel.org On Fri, Feb 22, 2019 at 8:45 AM Trond Myklebust wrote: > > On Fri, 2019-02-22 at 07:12 -0500, Dave Wysochanski wrote: > > Hi Olga, > > > > Do you have a reproducer for this? A number of months ago I did a > > significant amount of testing with half-closed connections, after we > > had reports of connections stuck in FIN_WAIT2 in some older kernels. > > What I found was with kernels that had the tcp keepalives (commit > > 7f260e8575bf53b93b77978c1e39f8e67612759c), I could only reproduce a > > hang of a few minutes, after which time the tcp keepalive code would > > reset the connection. > > > > That said it was a while ago and something subtle may have changed. > > Also I'm not not sure if your header implies an indefinite hang or > > just > > a few minutes. > > > > Thanks. > > > > > > On Wed, 2019-02-20 at 09:56 -0500, Olga Kornievskaia wrote: > > > From: Olga Kornievskaia > > > > > > When server replies with an ACK to client's FIN/ACK, client ends > > > up stuck in a TCP_FIN_WAIT2 state and client's mount hangs. > > > Instead, make sure to close and reset client's socket and transport > > > when transitioned into that state. > Hi Trond, > So, please do note that we do not want to ignore the FIN_WAIT2 state But we do ignore the FIN_WAIT2 state. > because it implies that the server has not closed the socket on its > side. That's correct. > That again means that we cannot re-establish a connection using > the same source IP+port to the server, which is problematic for > protocols such as NFSv3 which rely on standard duplicate reply cache > for correct replay semantics. that's exactly what's happening that a client is unable to establish a new connection to the server. With the patch, the client does an RST and it re-uses the port and all is well for NFSv3. > This is why we don't just set the TCP_LINGER2 socket option and call > sock_release(). The choice to try to wait it out is deliberate because > the alternative is that we end up with busy-waiting re-connection > attempts. Why would it busy-wait? In my testing, RST happens and new connection is established? > > Cheers > Trond > -- > Trond Myklebust > Linux NFS client maintainer, Hammerspace > trond.myklebust@hammerspace.com > >