From mboxrd@z Thu Jan 1 00:00:00 1970 From: Mauricio Faria de Oliveira Subject: Re: [PATCH] scsi: do not requeue requests unaligned with device sector size Date: Wed, 21 Dec 2016 21:11:09 -0200 Message-ID: References: <1482199347-9128-1-git-send-email-mauricfo@linux.vnet.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org To: "Martin K. Petersen" , Christoph Hellwig , Hannes Reinecke Cc: jejb@linux.vnet.ibm.com, linux-scsi@vger.kernel.org, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, gpiccoli@linux.vnet.ibm.com List-Id: linux-scsi@vger.kernel.org On 12/21/2016 05:50 AM, Christoph Hellwig wrote: > How do you even get an unaligned residual count? Except for SES > processor devices (which will only issue BLOCK_PC commands) this is > not allowed by SPC: > > "The residual count shall be reported in bytes if the peripheral device > type in the destination target descriptor is 03h (i.e., processor device), > and in destination device blocks for all other device type codes. On 12/21/2016 06:09 AM, Hannes Reinecke wrote: > Which actually would be pretty much my objection, too. > > This would only be applicable for 512e drives, where we _might_ end up > with a residual smaller than the physical sector size. > But that should be handled by firmware; after all, that's what the 'e' > implies, right? On 12/21/2016 12:01 PM, Martin K. Petersen wrote: > I agree with Christoph and Hannes. Some of this falls into the gray area > that's outside of the T10 spec (HBA programming interface guarantees) > but it seems like a deficiency in the HBA to report a byte count that's > not a multiple of the logical block size. A block can't be partially > written. Either it made it or it didn't. Regardless of how the I/O is > being broken up into frames at the transport level and at which offset > the transfer was interrupted. Christoph, Hannes, Martin, Thank you all for your comments and pointers to the documentation/spec. I'll carry it on with the HBA and storage folks. cheers, -- Mauricio Faria de Oliveira IBM Linux Technology Center