Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755866Ab3I3Pth (ORCPT ); Mon, 30 Sep 2013 11:49:37 -0400 Received: from mx1.redhat.com ([209.132.183.28]:40226 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755073Ab3I3Ptg (ORCPT ); Mon, 30 Sep 2013 11:49:36 -0400 Message-ID: <52498F68.8050200@redhat.com> Date: Mon, 30 Sep 2013 09:49:12 -0500 From: Ric Wheeler User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130805 Thunderbird/17.0.8 MIME-Version: 1.0 To: Miklos Szeredi CC: "J. Bruce Fields" , "Myklebust, Trond" , Zach Brown , Anna Schumaker , Kernel Mailing List , Linux-Fsdevel , "linux-nfs@vger.kernel.org" , "Schumaker, Bryan" , "Martin K. Petersen" , Jens Axboe , Mark Fasheh , Joel Becker , Eric Wong Subject: Re: [RFC] extending splice for copy offloading References: <20130925210742.GG30372@lenny.home.zabbo.net> <20130926185508.GO30372@lenny.home.zabbo.net> <5244A68F.906@redhat.com> <20130927200550.GA22640@fieldses.org> <20130927205013.GZ30372@lenny.home.zabbo.net> <4FA345DA4F4AE44899BD2B03EEEC2FA9467EF2D7@SACEXCMBX04-PRD.hq.netapp.com> <52474839.2080201@redhat.com> <20130930143432.GG16579@fieldses.org> <52499026.3090802@redhat.com> <52498AA8.2090204@redhat.com> <52498DB6.7060901@redhat.com> In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1322 Lines: 33 On 09/30/2013 10:46 AM, Miklos Szeredi wrote: > On Mon, Sep 30, 2013 at 4:41 PM, Ric Wheeler wrote: >> The way the array based offload (and some software side reflink works) is >> not a byte by byte copy. We cannot assume that a valid count can be returned >> or that such a count would be an indication of a sequential segment of good >> data. The whole thing would normally have to be reissued. >> >> To make that a true assumption, you would have to mandate that in each of >> the specifications (and sw targets)... > You're missing my point. > > - user issues SIZE_MAX splice request > - fs issues *64M* (or whatever) request to offload > - when that completes *fully* then we return 64M to userspace > - if it completes partially, then we return an error to userspace > > Again, wouldn't that work? > > Thanks, > Miklos Yes, if you send a copy offload command and it works, you can assume that it worked fully. It would be pretty interesting if that were not true :) If it fails, we cannot assume anything about partial completion. Ric -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/