Return-Path: Received: from aserp1040.oracle.com ([141.146.126.69]:48367 "EHLO aserp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751789AbcHXTh1 (ORCPT ); Wed, 24 Aug 2016 15:37:27 -0400 Content-Type: text/plain; charset=windows-1252 Mime-Version: 1.0 (Mac OS X Mail 9.3 \(3124\)) Subject: Re: READ during state recovery uses zero stateid From: Chuck Lever In-Reply-To: <832771A7-EF94-475C-871E-EE9499EC75B3@primarydata.com> Date: Wed, 24 Aug 2016 15:37:18 -0400 Cc: Anna Schumaker , Linux NFS Mailing List Message-Id: <56448609-05CA-493F-B98A-A2DCAB7909E9@oracle.com> References: <87A94B50-A9D5-44FF-9F78-F916C98E6767@primarydata.com> <182FCDA3-1BD7-436F-88A3-B29AAD7E6BAE@oracle.com> <832771A7-EF94-475C-871E-EE9499EC75B3@primarydata.com> To: Trond Myklebust Sender: linux-nfs-owner@vger.kernel.org List-ID: > On Aug 24, 2016, at 3:05 PM, Trond Myklebust wrote: > >> >> On Aug 24, 2016, at 14:47, Chuck Lever wrote: >> >> >>> On Aug 24, 2016, at 2:23 PM, Trond Myklebust wrote: >>> >>>> >>>> On Aug 24, 2016, at 14:10, Chuck Lever wrote: >>>> >>>> Hi- >>>> >>>> I have a wire capture that shows this race while a simple I/O workload is >>>> running: >>>> >>>> 0. The client reconnects after a network partition >>>> 1. The client sends a couple of READ requests >>>> 2. The client independently discovers its lease has expired >>>> 3. The client establishes a fresh lease >>>> 4. The client destroys open, lock, and delegation stateids for the file >>>> that was open under the previous lease >>>> 5. The client issues a new OPEN to recover state for that file >>>> 6. The server replies to the READs in step 1. with NFS4ERR_EXPIRED >>>> 7. The client turns the READs around immediately using the current open >>>> stateid for that file, which is the zero stateid >>>> 8. The server replies NFS4_OK to the OPEN from step 5 >>>> >>>> If I understand the code correctly, if the server happened to send those >>>> READ replies after its OPEN reply (rather than before), the client would >>>> have used the recovered open stateid instead of the zero stateid when >>>> resending the READ requests. >>>> >>>> Would it be better if the client recognized there is state recovery in >>>> progress, and then waited for recovery to complete, before retrying the >>>> READs? >>>> >>> >>> Why isn?t the session draining taking care of ensuring the READs don?t happen until after recovery is done? >> >> This is NFSv4.0. (Apologies, I recalled NFS4ERR_EXPIRED had been removed >> from NFSv4.1, but I see that I was mistaken). >> >> Here's step 1 and 2, exactly. After the partition heals, the client sends: >> >> C READ >> C GETATTR >> C READ >> C RENEW >> >> The server responds to the RENEW first with GSS_CTXPROBLEM. The client's >> gssd connects and establishes a fresh GSS context. The client sends the >> RENEW again with the fresh context, and the server responds NFS4ERR_EXPIRED. >> This triggers step 3. >> >> The replies for those READ calls are in step 6., after state recovery >> has started. > > This is what I?m confused about: Normally, I?d expect the NFSv4.0 code to drain, due to the checks in nfs40_setup_sequence(). > > IOW: there should be 2 steps > > 2.5) Call nfs4_drain_slot_tbl() and wait for operations to complete > 2.6) Process the NFS4ERR_EXPIRED errors returned by the READ requests sent in (1). > > before we get to recovering the lease in (3)... My kernel is missing commit 5cae02f42793 ("NFSv4: Always drain the slot table before re-establishing the lease"). I can give that a try, thank you! -- Chuck Lever