From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933395AbcIOLjZ (ORCPT ); Thu, 15 Sep 2016 07:39:25 -0400 Received: from bombadil.infradead.org ([198.137.202.9]:37761 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1763607AbcIOLjW (ORCPT ); Thu, 15 Sep 2016 07:39:22 -0400 Date: Thu, 15 Sep 2016 04:39:18 -0700 From: Christoph Hellwig To: Alex Bligh Cc: Wouter Verhelst , Josef Bacik , linux-block@vger.kernel.org, Markus Pargmann , kernel-team@fb.com, "nbd-general@lists.sourceforge.net" , "linux-kernel@vger.kernel.org" , Eric Blake Subject: Re: [Nbd] [RESEND][PATCH 0/5] nbd improvements Message-ID: <20160915113918.GB23259@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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <27B346AF-F144-4770-BE38-446A66E71326@alex.org.uk> 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 12:09:28PM +0100, Alex Bligh wrote: > A more general point is that with multiple queues requests > may be processed in a different order even by those servers that > currently process the requests in strict order, or in something > similar to strict order. The server is permitted by the spec > (save as mandated by NBD_CMD_FLUSH and NBD_CMD_FLAG_FUA) to > process commands out of order anyway, but I suspect this has > to date been little tested. The Linux kernel does not assume any synchroniztion between block I/O commands. So any sort of synchronization a protocol does is complete overkill for us.