From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933791AbcIOMUQ (ORCPT ); Thu, 15 Sep 2016 08:20:16 -0400 Received: from bombadil.infradead.org ([198.137.202.9]:55262 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756187AbcIOMUL (ORCPT ); Thu, 15 Sep 2016 08:20:11 -0400 Date: Thu, 15 Sep 2016 05:20:08 -0700 From: Christoph Hellwig To: Wouter Verhelst Cc: Christoph Hellwig , Alex Bligh , "nbd-general@lists.sourceforge.net" , linux-block@vger.kernel.org, Josef Bacik , "linux-kernel@vger.kernel.org" , Markus Pargmann , kernel-team@fb.com Subject: Re: [Nbd] [RESEND][PATCH 0/5] nbd improvements Message-ID: <20160915122008.GB1155@infradead.org> References: <1473369130-22986-1-git-send-email-jbacik@fb.com> <20160909200203.phhvodsfs7ymukfp@grep.be> <20160915104935.ohuwgq2chsedz6fl@grep.be> <27B346AF-F144-4770-BE38-446A66E71326@alex.org.uk> <20160915112936.vb7zxe7k6rvczosg@grep.be> <20160915114005.GC23259@infradead.org> <20160915115217.GB6411@infradead.org> <20160915120159.2o5lb7rvkjndzayh@grep.be> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20160915120159.2o5lb7rvkjndzayh@grep.be> User-Agent: Mutt/1.6.1 (2016-04-27) X-SRS-Rewrite: SMTP reverse-path rewritten from by bombadil.infradead.org. See http://www.infradead.org/rpr.html Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Sep 15, 2016 at 02:01:59PM +0200, Wouter Verhelst wrote: > Yes. There was some discussion on that part, and we decided that setting > the flag doesn't hurt, but the spec also clarifies that using it on READ > does nothing, semantically. > > > The problem is that there are clients in the wild which do set it on > READ, so it's just a matter of "be liberal in what you accept". Note that FUA on READ in SCSI and NVMe does have a meaning - it requires you to bypass any sort of cache on the target. I think it's an wrong defintion because it mandates implementation details that aren't observable by the initiator, but it's still the spec wording and nbd diverges from it. That's not nessecarily a bad thing, but a caveat to look out for.