From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-it0-f66.google.com ([209.85.214.66]:34781 "EHLO mail-it0-f66.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750785AbcKQVxq (ORCPT ); Thu, 17 Nov 2016 16:53:46 -0500 Received: by mail-it0-f66.google.com with SMTP id o1so18140429ito.1 for ; Thu, 17 Nov 2016 13:53:45 -0800 (PST) MIME-Version: 1.0 In-Reply-To: <1479419127.33885.5.camel@primarydata.com> References: <20161117163101.GA19161@fieldses.org> <1479404750.33885.1.camel@primarydata.com> <20161117193239.GD20937@fieldses.org> <20161117201753.GF20937@fieldses.org> <20161117204618.GG20937@fieldses.org> <20161117212601.GA23130@fieldses.org> <1479419127.33885.5.camel@primarydata.com> From: Olga Kornievskaia Date: Thu, 17 Nov 2016 16:53:44 -0500 Message-ID: Subject: Re: NFS: nfs4_reclaim_open_state: Lock reclaim failed! log spew To: Trond Myklebust Cc: "bfields@fieldses.org" , "tibbs@math.uh.edu" , "linux-nfs@vger.kernel.org" Content-Type: text/plain; charset=UTF-8 Sender: linux-nfs-owner@vger.kernel.org List-ID: On Thu, Nov 17, 2016 at 4:45 PM, Trond Myklebust wrote: > On Thu, 2016-11-17 at 16:26 -0500, bfields@fieldses.org wrote: >> On Thu, Nov 17, 2016 at 04:05:32PM -0500, Olga Kornievskaia wrote: >> > >> > On Thu, Nov 17, 2016 at 3:46 PM, bfields@fieldses.org >> > wrote: >> > > >> > > On Thu, Nov 17, 2016 at 03:29:11PM -0500, Olga Kornievskaia >> > > wrote: >> > > > >> > > > On Thu, Nov 17, 2016 at 3:17 PM, bfields@fieldses.org >> > > > wrote: >> > > > > >> > > > > On Thu, Nov 17, 2016 at 02:58:12PM -0500, Olga Kornievskaia >> > > > > wrote: >> > > > > > >> > > > > > On Thu, Nov 17, 2016 at 2:32 PM, bfields@fieldses.org >> > > > > > wrote: >> > > > > > > >> > > > > > > On Thu, Nov 17, 2016 at 05:45:52PM +0000, Trond Myklebust >> > > > > > > wrote: >> > > > > > > > >> > > > > > > > On Thu, 2016-11-17 at 11:31 -0500, J. Bruce Fields >> > > > > > > > wrote: >> > > > > > > > > >> > > > > > > > > On Wed, Nov 16, 2016 at 02:55:05PM -0600, Jason L >> > > > > > > > > Tibbitts III wrote: >> > > > > > > > > > >> > > > > > > > > > >> > > > > > > > > > I'm replying to a rather old message, but the issue >> > > > > > > > > > has just now >> > > > > > > > > > popped >> > > > > > > > > > back up again. >> > > > > > > > > > >> > > > > > > > > > To recap, a client stops being able to access _any_ >> > > > > > > > > > mount on a >> > > > > > > > > > particular server, and "NFS: >> > > > > > > > > > nfs4_reclaim_open_state: Lock reclaim >> > > > > > > > > > failed!" appears several hundred times per second >> > > > > > > > > > in the kernel >> > > > > > > > > > log. >> > > > > > > > > > The load goes up by one for ever process attempting >> > > > > > > > > > to access any >> > > > > > > > > > mount >> > > > > > > > > > from that particular server. Mounts to other >> > > > > > > > > > servers are fine, and >> > > > > > > > > > other clients can mount things from that one server >> > > > > > > > > > without >> > > > > > > > > > problems. >> > > > > > > > > > >> > > > > > > > > > When I kill every process keeping that particular >> > > > > > > > > > mount active and >> > > > > > > > > > then >> > > > > > > > > > umount it, I see: >> > > > > > > > > > >> > > > > > > > > > NFS: nfs4_reclaim_open_state: unhandled error >> > > > > > > > > > -10068 >> > > > > > > > > >> > > > > > > > > NFS4ERR_RETRY_UNCACHED_REP. >> > > > > > > > > >> > > > > > > > > So, you're using NFSv4.1 or 4.2, and the server >> > > > > > > > > thinks that the >> > > > > > > > > client >> > > > > > > > > has reused a (slot, sequence number) pair, but the >> > > > > > > > > server doesn't >> > > > > > > > > have a >> > > > > > > > > cached response to return. >> > > > > > > > > >> > > > > > > > > Hard to know how that happened, and it's not shown in >> > > > > > > > > the below. >> > > > > > > > > Sounds like a bug, though. >> > > > > > > > >> > > > > > > > ...or a Ctrl-C.... >> > > > > > > >> > > > > > > How does that happen? >> > > > > > > >> > > > > > >> > > > > > If I may chime in... >> > > > > > >> > > > > > Bruce, when an application sends a Ctrl-C and clients's >> > > > > > session slot >> > > > > > has sent out an RPC but didn't process the reply, the >> > > > > > client doesn't >> > > > > > know if the server processed that sequence id or not. In >> > > > > > that case, >> > > > > > the client doesn't increment the sequence number. Normally >> > > > > > the client >> > > > > > would handle getting such an error by retrying again (and >> > > > > > resetting >> > > > > > the slots) but I think during recovery operation the client >> > > > > > handles >> > > > > > errors differently (by just erroring). I believe the >> > > > > > reasoning that we >> > > > > > don't want to be stuck trying to recover from the recovery >> > > > > > from the >> > > > > > recovery etc... >> > > > > >> > > > > So in that case the client can end up sending a different rpc >> > > > > reusing >> > > > > the old slot and sequence number? >> > > > >> > > > Correct. >> > > >> > > So that could get UNCACHED_REP as the response. But if you're >> > > very >> > > unlucky, couldn't this also happen?: >> > > >> > > 1) the compound previously sent on that slot was >> > > processed by >> > > the server and cached >> > > 2) the compound you're sending now happens to have the >> > > same set >> > > of operations >> > > >> > > with the result that the client doesn't detect that the reply was >> > > actually to some other rpc, and instead it returns bad data to >> > > the >> > > application? >> > >> > If you are sending exactly the same operations and arguments, then >> > why >> > is a reply from the cache would lead to bad data? >> >> That would probably be fine, I was wondering what would happen if you >> sent the same operation but different arguments. > >> So the original cancelled operation is something like >> PUTFH(fh1)+OPEN("foo")+GETFH, and the new one is >> PUTFH(fh2)+OPEN("bar")+GETFH. In theory couldn't the second one >> succeed >> and leave the client thinking it had opened (fh2, bar) when the >> filehandle it got back was really for (fh1, foo)? >> > > The client would receive a filehandle for fh1/"foo", so it would apply > any state it thought it had received to that file. However, normally, > I'd expect to see a NFS4ERR_FALSE_RETRY in this case. I see Bruce's point that if the server only looks up the cache based on the seqid and slot# and doesn't have like a hash of the content which I could see is expensive, then the client in this case would get into trouble of thinking it opened "bar" but really it's "foo". Spec says: Section 18.46.3 If the client reuses a slot ID and sequence ID for a completely different request, the server MAY treat the request as if it is a retry of what it has already executed. The server MAY however detect the client's illegal reuse and return NFS4ERR_SEQ_FALSE_RETRY. What is "a completely different request". From the client's point of view sending different args would constitute a different request. But in any case it's a "MAY" so client can't depend on this being implemented.