Return-Path: linux-nfs-owner@vger.kernel.org Received: from bombadil.infradead.org ([198.137.202.9]:38932 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932317AbbBDIQ3 (ORCPT ); Wed, 4 Feb 2015 03:16:29 -0500 Date: Wed, 4 Feb 2015 00:16:24 -0800 From: Christoph Hellwig To: Trond Myklebust Cc: linux-nfs@vger.kernel.org, Olga.Kornievskaia@netapp.com Subject: Re: [PATCH 1/2] NFSv4.1: Ask for no delegation on OPEN if using O_DIRECT Message-ID: <20150204081624.GA16543@infradead.org> References: <1423000784-93180-1-git-send-email-trond.myklebust@primarydata.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <1423000784-93180-1-git-send-email-trond.myklebust@primarydata.com> Sender: linux-nfs-owner@vger.kernel.org List-ID: On Tue, Feb 03, 2015 at 04:59:43PM -0500, Trond Myklebust wrote: > If we're using NFSv4.1, then we have the ability to let the server know > whether or not we believe that returning a delegation as part of our OPEN > request would be useful. > The feature needs to be used with care, since the client sending the request > doesn't necessarily know how other clients are using that file, and how > they may be affected by the delegation. > For this reason, our initial use of the feature will be to let the server > know when the client believes that handing out a delegation would not be > useful. > The first application for this function is when opening the file using > O_DIRECT. I can't see why O_DIRECT openers would not want to use a delegation, can you explain your rationale?