From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1768962Ab2KOUbT (ORCPT ); Thu, 15 Nov 2012 15:31:19 -0500 Received: from mail.linux-iscsi.org ([67.23.28.174]:35484 "EHLO linux-iscsi.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1768923Ab2KOUbR (ORCPT ); Thu, 15 Nov 2012 15:31:17 -0500 Subject: RE: [PATCH 3/3] target/iblock: Add WRITE_SAME w/ UNMAP=0 emulation support From: "Nicholas A. Bellinger" To: "Elliott, Robert (Server Storage)" Cc: Christoph Hellwig , Christoph Hellwig , target-devel , linux-scsi , linux-kernel , "Martin K. Petersen" In-Reply-To: <94D0CD8314A33A4D9D801C0FE68B40294CCF8D45@G9W0745.americas.hpqcorp.net> 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> Content-Type: text/plain; charset="UTF-8" Date: Thu, 15 Nov 2012 12:31:15 -0800 Message-ID: <1353011475.4447.31.camel@haakon2.linux-iscsi.org> Mime-Version: 1.0 X-Mailer: Evolution 2.30.3 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Robert, On Thu, 2012-11-15 at 20:01 +0000, Elliott, Robert (Server Storage) wrote: > 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. > > 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. > Thanks for the heads up here.. I'm making the slight change to the -v2 patch series that just went out to always check the max_write_same_len value for both WRITE_SAME w/ UNMAP=[1,0] cases. Thank you, --nab