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=-2.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_MUTT 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 E0A5EC10F0E for ; Thu, 18 Apr 2019 23:42:39 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id B1AEC20675 for ; Thu, 18 Apr 2019 23:42:39 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1725890AbfDRXmj (ORCPT ); Thu, 18 Apr 2019 19:42:39 -0400 Received: from fieldses.org ([173.255.197.46]:42048 "EHLO fieldses.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725855AbfDRXmi (ORCPT ); Thu, 18 Apr 2019 19:42:38 -0400 Received: by fieldses.org (Postfix, from userid 2815) id 811FC3EB; Thu, 18 Apr 2019 19:42:38 -0400 (EDT) Date: Thu, 18 Apr 2019 19:42:38 -0400 From: "bfields@fieldses.org" To: Trond Myklebust Cc: "smayhew@redhat.com" , "linux-nfs@vger.kernel.org" , "jlayton@kernel.org" Subject: Re: [PATCH] nfsd: CB_RECALL can race with FREE_STATEID Message-ID: <20190418234238.GA3761@fieldses.org> References: <20190418132400.24161-1-smayhew@redhat.com> <20190418151312.GB29274@fieldses.org> <20190418205024.GB15226@coeurl.usersys.redhat.com> <15806b00f7ba569a109549eb551bb116d981226d.camel@hammerspace.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <15806b00f7ba569a109549eb551bb116d981226d.camel@hammerspace.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-nfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-nfs@vger.kernel.org On Thu, Apr 18, 2019 at 10:03:09PM +0000, Trond Myklebust wrote: > On Thu, 2019-04-18 at 16:50 -0400, Scott Mayhew wrote: > > On Thu, 18 Apr 2019, J. Bruce Fields wrote: > > > > > On Thu, Apr 18, 2019 at 09:24:00AM -0400, Scott Mayhew wrote: > > > > While trying to track down some issues involving large numbers of > > > > delegations being recalled/revoked, I caught the server setting > > > > SEQ4_STATUS_CB_PATH_DOWN while the client was actively responding > > > > to > > > > CB_RECALLs. It turns out that the client had already done a > > > > TEST_STATEID and FREE_STATEID for a delegation being recalled by > > > > the > > > > time it received the CB_RECALL. > > > > > > That's interesting, thanks! > > > > > > This exception seems awfully narrow, though. > > > > > > If we get back any NFS-level error at all, then I think the > > > callback > > > channel is working (am I wrong?) > > > > Correct, if the client replies with either NFS4ERR_DELAY or > > NFS4ERR_BAD_STATEID, the server will retry 1 time (see dl_retries). > > After that, we fall thru and nfsd4_cb_recall_done() returns -1 which > > causes the SEQ4_STATUS_CB_PATH_DOWN flag to be set. > > There is no handling of NFS4ERR_DELAY in nfsd4_cb_recall_done(). > > As far as I can see, therefore, if the client returns NFS4ERR_DELAY > (which it usually does if it is already in the process of returning the > delegation) then the recall will fail immediately. We should fix that, though it doesn't sound like it matters much in that particular case. The success or failure of a recall isn't actually all that interesting, all that matters is whether we get the eventual DELEGRETURN. --b.