Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751368AbaALLtn (ORCPT ); Sun, 12 Jan 2014 06:49:43 -0500 Received: from mail-ee0-f48.google.com ([74.125.83.48]:55894 "EHLO mail-ee0-f48.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751198AbaALLtl (ORCPT ); Sun, 12 Jan 2014 06:49:41 -0500 Message-ID: <52D28150.8090908@dev.mellanox.co.il> Date: Sun, 12 Jan 2014 13:49:36 +0200 From: Sagi Grimberg User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:24.0) Gecko/20100101 Thunderbird/24.2.0 MIME-Version: 1.0 To: "Martin K. Petersen" , Andy Grover CC: "Nicholas A. Bellinger" , Sagi Grimberg , "Nicholas A. Bellinger" , target-devel , linux-scsi , linux-kernel , Christoph Hellwig , Hannes Reinecke , Or Gerlitz Subject: Re: [PATCH 07/14] target/sbc: Add P_TYPE + PROT_EN bits to READ_CAPACITY_16 References: <1389212157-14540-1-git-send-email-nab@daterainc.com> <1389212157-14540-8-git-send-email-nab@daterainc.com> <52CE78EB.60108@mellanox.com> <1389334891.5567.373.camel@haakon3.risingtidesystems.com> <52D04F1A.2000808@redhat.com> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 1/10/2014 10:46 PM, Martin K. Petersen wrote: >>>>>> "Andy" == Andy Grover writes: > Andy> Yes, don't you need FORMAT UNIT because protection information is > Andy> going to mean the pi-enabled lun will need to report less blocks? > > Modern disk drives won't shrink when you reformat them with PI. This is > a result of an IDEMA agreement about LBA counts. > > And if you create a 10GB PI LUN on an array you'll get 10GB for data. > > Andy> The ramdisk backstore changes in this series allocate extra space > Andy> for PI info, but my understanding was that especially for > Andy> emulation with block and fileio backstores, everything needs to go > Andy> in the same amount of space. > > For both file and block I'd recommend we store the PI in a separate > block device or file unless the backing device is PI-capable. > > Andy> Furthermore, if we want PI info stored along with the blocks, then > Andy> block and fileio backstore formats are no longer going to be 1:1 > Andy> -- requiring offset calculations, non-aligned read-modify-write, > Andy> and all that unpleasantness to be handled? > > I only think interleaved makes sense if you're passing the PI through > instead of emulating. > I agree, I implemented interleaved mode just as a proof of concept that our HW can perform offload in that manner. I assume we can stick with non-interleaved, although it can be added as a user option. Sagi. -- 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/