Return-Path: linux-nfs-owner@vger.kernel.org Received: from fieldses.org ([174.143.236.118]:39237 "EHLO fieldses.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751370Ab2CHU5j (ORCPT ); Thu, 8 Mar 2012 15:57:39 -0500 Date: Thu, 8 Mar 2012 15:57:37 -0500 From: "J. Bruce Fields" To: "Myklebust, Trond" Cc: Olga Kornievskaia , Miklos Szeredi , "linux-nfs@vger.kernel.org" , "linux-fsdevel@vger.kernel.org" , "linux-kernel@vger.kernel.org" Subject: Re: [PATCH 2/2] NFSv4: Return the delegation if the server returns NFS4ERR_OPENMODE Message-ID: <20120308205737.GC9273@fieldses.org> References: <87k42yjb0c.fsf@tucsk.pomaz.szeredi.hu> <1331160049-3842-1-git-send-email-Trond.Myklebust@netapp.com> <1331160049-3842-2-git-send-email-Trond.Myklebust@netapp.com> <1331160049-3842-3-git-send-email-Trond.Myklebust@netapp.com> <1331230525.2472.39.camel@lade.trondhjem.org> <20120308204205.GB9273@fieldses.org> <1331239814.11759.1.camel@lade.trondhjem.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <1331239814.11759.1.camel@lade.trondhjem.org> Sender: linux-nfs-owner@vger.kernel.org List-ID: On Thu, Mar 08, 2012 at 08:50:14PM +0000, Myklebust, Trond wrote: > On Thu, 2012-03-08 at 15:42 -0500, J. Bruce Fields wrote: > > On Thu, Mar 08, 2012 at 03:23:34PM -0500, Olga Kornievskaia wrote: > > > On Thu, Mar 8, 2012 at 1:15 PM, Myklebust, Trond > > > wrote: > > > > On Thu, 2012-03-08 at 12:52 -0500, Olga Kornievskaia wrote: > > > >> wouldn't it be better for you to proactively return a read delegation > > > >> then unnecessarily erroring? > > > > > > > > If nobody else holds a delegation, then the NFS client is actually > > > > allowed to keep its read delegation while writing to the file. It does > > > > admittedly need to request an OPEN stateid for write in that case... > > > > (See section 10.4 of RFC3530bis draft 16) > > > > > > If we both agree that there has to be a request for an open stateid for > > > a write, then instead of returning the read delegation if the client receives > > > err_openmode (when it send the request with read delegation stateid > > > as you said per 3560bis), can't the client resend the setattr with the open > > > stateid? The ordering of the stateid usage is a "should" and not a "must". > > > > > > In rfc5661, it really doesn't make sense to ever send a setattr with > > > a read delegation stateid. According to 9.1.2, the server "MUST" return > > > err_open_mode" error in that case. > > > > > > I gather you are in this case dealing with 4.0 delegations. But I wonder > > > if you'll do something else for 4.1 delegation then? > > > > 3530bis has the same language ("...must verify that the access mode > > allows writing and return an NFS4ERR_OPENMODE error if it does not"). > > OK, so we shouldn't send the delegation stateid either for v4 or v4.1. > However should we pre-emptively return the delegation? I've been > assuming not. The server's only legal option is to recall it, so it seems odd not to pre-emptively return--but as you say there's nothing to prevent the server from then handing one right back, possibly before you get a chance to send the setattr. (And the linux server might well do that--maybe it should have some heuristic not to hand out a delegation that was just returned--not so much for this case as just because a return is a sign that the delegation isn't useful to that client.) --b.