From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752126Ab2KSLi2 (ORCPT ); Mon, 19 Nov 2012 06:38:28 -0500 Received: from mail-pa0-f46.google.com ([209.85.220.46]:34922 "EHLO mail-pa0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750808Ab2KSLi0 (ORCPT ); Mon, 19 Nov 2012 06:38:26 -0500 Message-ID: <50AA1A2A.2070504@redhat.com> Date: Mon, 19 Nov 2012 12:38:18 +0100 From: Paolo Bonzini User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:16.0) Gecko/20121016 Thunderbird/16.0.1 MIME-Version: 1.0 To: "Elliott, Robert (Server Storage)" CC: Christoph Hellwig , "Nicholas A. Bellinger" , Christoph Hellwig , target-devel , linux-scsi , linux-kernel , "Martin K. Petersen" Subject: Re: [PATCH 3/3] target/iblock: Add WRITE_SAME w/ UNMAP=0 emulation support References: <1352405238-23267-1-git-send-email-nab@linux-iscsi.org> <1352405238-23267-4-git-send-email-nab@linux-iscsi.org> <20121115110432.GD28956@infradead.org> <1353007786.4447.29.camel@haakon2.linux-iscsi.org> <20121115193235.GA5714@lst.de> <94D0CD8314A33A4D9D801C0FE68B40294CCF8D45@G9W0745.americas.hpqcorp.net> In-Reply-To: <94D0CD8314A33A4D9D801C0FE68B40294CCF8D45@G9W0745.americas.hpqcorp.net> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Il 15/11/2012 21:01, Elliott, Robert (Server Storage) ha scritto: > WRITE SAME always has a payload, regardless of the UNMAP bit value. > > For WRITE SAME with UNMAP=0, it's extremely important; that's how > what to write is specified. > > For WRITE SAME with UNMAP=1, the device server is required to check > that the payload matches the data that is returned for unmapped LBAs. > lf LBPRZ=1 (read zeros for unmapped LBAs), that means checking that > the payload has all zeros. In sbc3r33, this rule is tucked away in > model section 4.7.3.4.3, not the command section 5.41. Does that mean that LBPRZ=0, LPBWS=1 is practically an invalid combination? Because there's no real way for the device server to perform the check successfully. Paolo > I would like to change that rule (it's a nuisance and a performance > burden), but that's the current rule going into SBC-3 letter ballot. > > Changing WRITE SAME with UNMAP=1 to ignore the payload would provide > essentially the same functionality as changing the UNMAP command to > be mandatory, not just a hint; both approaches have been discussed.