Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751367AbaALMoA (ORCPT ); Sun, 12 Jan 2014 07:44:00 -0500 Received: from userp1040.oracle.com ([156.151.31.81]:34500 "EHLO userp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751224AbaALMnz (ORCPT ); Sun, 12 Jan 2014 07:43:55 -0500 To: Sagi Grimberg Cc: "Martin K. Petersen" , "Nicholas A. Bellinger" , target-devel , linux-scsi , linux-kernel , Christoph Hellwig , Hannes Reinecke , Sagi Grimberg , Or Gerlitz , Nicholas Bellinger Subject: Re: [PATCH 09/14] target/configfs: Expose protection device attributes From: "Martin K. Petersen" Organization: Oracle Corporation References: <1389212157-14540-1-git-send-email-nab@daterainc.com> <1389212157-14540-10-git-send-email-nab@daterainc.com> <52D28807.2000004@dev.mellanox.co.il> Date: Sun, 12 Jan 2014 07:43:38 -0500 In-Reply-To: <52D28807.2000004@dev.mellanox.co.il> (Sagi Grimberg's message of "Sun, 12 Jan 2014 14:18:15 +0200") Message-ID: User-Agent: Gnus/5.130005 (Ma Gnus v0.5) Emacs/24.2 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain X-Source-IP: ucsinet22.oracle.com [156.151.31.94] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org >>>>> "Sagi" == Sagi Grimberg writes: >> The IP checksum is only supported by DIX between OS and initiator, >> not by the target. I guess we could signal to the initiator via a >> vendor-private VPD that IP checksum is supported directly. But now >> what we have hardware-accelerated T10 CRC I don't think it's a big >> deal. Sagi> shouldn't it stick around if it is not deprecated yet, the Sagi> transport is required to support ip-csum->CRC conversion anyhow. SBC mandates that the guard tag on the wire and on the target device be the T10 CRC. The IP checksum is a DIX-optimization for application-HBA exchanges. The only place you should support the IP checksum is in the initiator. Note that you could conceivably do a T10 CRC to IP checksum conversion on writes received by the target and store the IP checksum on disk. And then convert back to T10 CRC when the data is eventually read. But it makes no sense to do that given that you will have to do the T10 CRC calculation regardless. Even if the backing store is DIX-capable and supports the IP checksum. -- Martin K. Petersen Oracle Linux Engineering -- 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/