From patchwork Mon Dec 12 20:49:13 2016 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Wouter Verhelst X-Patchwork-Id: 705143 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Received: from lists.gnu.org (lists.gnu.org [208.118.235.17]) (using TLSv1 with cipher AES256-SHA (256/256 bits)) (No client certificate requested) by ozlabs.org (Postfix) with ESMTPS id 3tcw375jW2z9sdn for ; Tue, 13 Dec 2016 07:50:43 +1100 (AEDT) Received: from localhost ([::1]:33564 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1cGXYX-0001TW-Tu for incoming@patchwork.ozlabs.org; Mon, 12 Dec 2016 15:50:41 -0500 Received: from eggs.gnu.org ([2001:4830:134:3::10]:49354) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1cGXXP-0000ln-7A for qemu-devel@nongnu.org; Mon, 12 Dec 2016 15:49:32 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1cGXXK-0004CT-3k for qemu-devel@nongnu.org; Mon, 12 Dec 2016 15:49:31 -0500 Received: from [2a01:4f8:140:52e5::2] (port=35793 helo=latin.grep.be) by eggs.gnu.org with esmtps (TLS1.0:RSA_AES_128_CBC_SHA1:16) (Exim 4.71) (envelope-from ) id 1cGXXJ-0004B1-Ti for qemu-devel@nongnu.org; Mon, 12 Dec 2016 15:49:26 -0500 Received: from d54c66cc7.access.telenet.be ([84.198.108.199] helo=gangtai.grep.be) by latin.grep.be with esmtpsa (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.84_2) (envelope-from ) id 1cGXXD-0004K4-0H; Mon, 12 Dec 2016 21:49:19 +0100 Received: from wouter by gangtai.grep.be with local (Exim 4.88) (envelope-from ) id 1cGXX7-0003pv-Js; Mon, 12 Dec 2016 21:49:13 +0100 Date: Mon, 12 Dec 2016 21:49:13 +0100 From: Wouter Verhelst To: Eric Blake Message-ID: <20161212204913.oaatvexhnndyhhwa@grep.be> References: <20161212182119.dceppkzqb7gftsl5@grep.be> <20161212202615.llsqhojp2xztfao3@grep.be> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20161212202615.llsqhojp2xztfao3@grep.be> X-Speed: Gates' Law: Every 18 months, the speed of software halves. Organization: none User-Agent: NeoMutt/20161126 (1.7.1) X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 2a01:4f8:140:52e5::2 Subject: Re: [Qemu-devel] [Nbd] [PATCH v4] doc: Add NBD_CMD_BLOCK_STATUS extension X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: "nbd-general@lists.sourceforge.net" , Kevin Wolf , Vladimir Sementsov-Ogievskiy , "qemu-devel@nongnu.org" , Pavel Borzenkov , "Stefan stefanha@redhat. com" , "Denis V. Lunev" , Markus Pargmann , Paolo Bonzini , John Snow Errors-To: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org Sender: "Qemu-devel" On Mon, Dec 12, 2016 at 09:26:15PM +0100, Wouter Verhelst wrote: > > Do we still want to require servers to always send 16 extents (when not > > limited to exactly 1), or is it better to just state that as long as the > > server sends at least one extent (so that the client can make progress), > > then the server can shorten the reply if it is resource-intensive to > > provide details over the entire client request? > > Hrm, I wanted to drop that (I did drop another reference to that thing, > I though), but apparently I forgot. ...and I still did. I don't think it's worth sending another full diff from extension-structured-reply for that, but here's the diff from v5: diff --git a/doc/proto.md b/doc/proto.md index 526f71a..1d6db4b 100644 --- a/doc/proto.md +++ b/doc/proto.md @@ -1242,9 +1242,11 @@ interpret the "length" bytes of payload. Even if the client did not use the `NBD_CMD_FLAG_REQ_ONE` flag in its request, the server MAY return less descriptors in the reply than would be required to fully specify the whole range of requested - information to the client, if the number of descriptors would be - over 16 otherwise and looking up the information would be too - resource-intensive for the server. + information to the client, if looking up the information would be + too resource-intensive for the server, so long as at least one + extent is returned. Servers should however be aware that most + clients implementations will then simply ask for the next extent + instead. Regards,