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=-6.0 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no 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 626E4C48BCF for ; Wed, 9 Jun 2021 14:31:55 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 4B43A6139A for ; Wed, 9 Jun 2021 14:31:55 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235658AbhFIOds (ORCPT ); Wed, 9 Jun 2021 10:33:48 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]:42662 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235435AbhFIOdr (ORCPT ); Wed, 9 Jun 2021 10:33:47 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1623249112; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=VHuG7E95MyKXVux4DDaQuTDADWW8PX7v3iVWe19V4UA=; b=RaL3xgEy7iAY2b5StWG72wAC+qHg5vre1XSMjIu314Bc+uLF1jXgyCMMPuQVLq4yZhYsi6 UuGO5Bpp3m1OjvgvIaUf74TGap+bY5gm/CF4sE7zFBzl1FjXcKfPMif/GiOo9J2p9+PmdA g0mAYRmVuQOnBOaEuN6rUFqNxTrqAEY= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-76-D-uen-vpOtGPt2XdlGFfZA-1; Wed, 09 Jun 2021 10:31:38 -0400 X-MC-Unique: D-uen-vpOtGPt2XdlGFfZA-1 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 29CBE9F92C; Wed, 9 Jun 2021 14:31:37 +0000 (UTC) Received: from [172.16.176.1] (ovpn-64-2.rdu2.redhat.com [10.10.64.2]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 6332B9CA0; Wed, 9 Jun 2021 14:31:36 +0000 (UTC) From: "Benjamin Coddington" To: "Michael Wakabayashi" Cc: "Olga Kornievskaia" , "Trond Myklebust" , linux-nfs@vger.kernel.org, SteveD@redhat.com Subject: Re: NFSv4: Mounting NFS server which is down, blocks all other NFS mounts on same machine Date: Wed, 09 Jun 2021 10:31:34 -0400 Message-ID: In-Reply-To: References: <6ae47edc-2d47-df9a-515a-be327a20131d@RedHat.com> <43b719c36652cdaf110a50c84154fca54498e772.camel@hammerspace.com> MIME-Version: 1.0 Content-Type: text/plain; format=flowed X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 Precedence: bulk List-ID: X-Mailing-List: linux-nfs@vger.kernel.org On 9 Jun 2021, at 1:31, Michael Wakabayashi wrote: > Hi Olga, > > There seems to be a discrepancy between what you're seeing and what > we're seeing. > > So we were wondering if you can you please run these commands in your > Linux environment and paste the output of the mount command below? > $ sudo mkdir -p /tmp/mnt.dead > $ time sudo mount -o vers=4 -vvv 2.2.2.2:/fake_path /tmp/mnt.dead > > We'd like the mount command to specifically use "2.2.2.2:/fake_path" > since we know it is unreachable and outside your subnet. > We're hoping by mounting "2.2.2.2:/fake_path" you'll be able to > reproduce the same behavior that we're seeing. > > Also, if possible, a packet trace would be helpful: > $ sudo tcpdump -s 0 -w /tmp/nfsv4.pcap port 2049 > > On my Ubuntu VirtualMachine, I see this output: > ubuntu@mikes-ubuntu-21-04:~$ time sudo mount -o vers=4 -vvv > 2.2.2.2:/fake_path /tmp/mnt.dead > mount.nfs: timeout set for Wed Jun 9 05:12:15 2021 > mount.nfs: trying text-based options > 'vers=4,addr=2.2.2.2,clientaddr=10.162.132.231' > mount.nfs: mount(2): Connection timed out > mount.nfs: Connection timed out > real 3m1.257s > user 0m0.006s > sys 0m0.007s > > Thanks, Mike It looks to me like you and Olga are seeing the same thing, a wait through SYN retries scaling up from initial RTO for the number of tcp_syn_retries. It's not disputed that mounts waiting on the transport layer will block other mounts. It might be able to be changed: there's this torch: https://lore.kernel.org/linux-nfs/87378omld4.fsf@notabene.neil.brown.name/ ..or there may be another way we don't have to wait .. .. or tune tcp_syn_retries.. or RTO.. or something else (eBPF?). I think we're all strapped for time and problems like this usually get fixed by the folks feeling the most pain from them. Ben