From mboxrd@z Thu Jan 1 00:00:00 1970 From: FUJITA Tomonori Subject: Re: [PATCH 03/11] block: add rq->resid_len Date: Wed, 13 May 2009 00:00:47 +0900 Message-ID: <20090513000150H.fujita.tomonori@lab.ntt.co.jp> References: <4A080C9D.9000109@panasas.com> <20090511235852Z.fujita.tomonori@lab.ntt.co.jp> <4A093A34.3020101@panasas.com> Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit Return-path: Received: from sh.osrg.net ([192.16.179.4]:39965 "EHLO sh.osrg.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752229AbZELPFe (ORCPT ); Tue, 12 May 2009 11:05:34 -0400 In-Reply-To: <4A093A34.3020101@panasas.com> Sender: linux-ide-owner@vger.kernel.org List-Id: linux-ide@vger.kernel.org To: bharrosh@panasas.com Cc: fujita.tomonori@lab.ntt.co.jp, tj@kernel.org, axboe@kernel.dk, linux-kernel@vger.kernel.org, jeff@garzik.org, linux-ide@vger.kernel.org, James.Bottomley@HansenPartnership.com, linux-scsi@vger.kernel.org, bzolnier@gmail.com, petkovbb@googlemail.com, sshtylyov@ru.mvista.com, mike.miller@hp.com, Eric.Moore@lsi.com, stern@rowland.harvard.edu, zaitcev@redhat.com, Geert.Uytterhoeven@sonycom.com, sfr@canb.auug.org.au, grant.likely@secretlab.ca, paul.clements@steeleye.com, tim@cyberelk.net, jeremy@xensource.com, adrian@mcmen.demon.co.uk, oakad@yahoo.com, dwmw2@infradead.org, schwidefsky@de.ibm.com, ballabio_dario@emc.com, davem@davemloft.net, rusty@rustcorp.com.au, Markus.Lidel@shadowconnect.com, dgilbert@interlog.com, djwong@us.ibm.com On Tue, 12 May 2009 11:58:28 +0300 Boaz Harrosh wrote: > On 05/11/2009 05:59 PM, FUJITA Tomonori wrote: > > On Mon, 11 May 2009 14:31:41 +0300 > > Boaz Harrosh wrote: > > > >>>>> diff --git a/drivers/scsi/libsas/sas_expander.c b/drivers/scsi/libsas/sas_expander.c > >>>>> index 3da02e4..6605ec9 100644 > >>>>> --- a/drivers/scsi/libsas/sas_expander.c > >>>>> +++ b/drivers/scsi/libsas/sas_expander.c > >>>>> @@ -1936,12 +1936,8 @@ int sas_smp_handler(struct Scsi_Host *shost, struct sas_rphy *rphy, > >>>>> bio_data(rsp->bio), rsp->data_len); > >>>>> if (ret > 0) { > >>>>> /* positive number is the untransferred residual */ > >>>>> - rsp->data_len = ret; > >>>>> - req->data_len = 0; > >>>>> + rsp->resid_len = ret; > >>>>> ret = 0; > >>>>> - } else if (ret == 0) { > >>>>> - rsp->data_len = 0; > >>>>> - req->data_len = 0; > >>>>> } > >>>>> > >>>>> return ret; > >>>> This is actually a bug fix, as well as a strait conversion > >>> Can you elaborate a bit about the bug fix part? > >>> > >> Nothing big really, just that before (according to the comment), the theoretical > >> negative case would be full-residual. and now it is zero (untouched). > >> > >> I know that in iscsi a negative residual is possible which means over-flow. That is: > >> the target had more data to give then the buffer had space for. (which is not an error at all) > > > > Hmm, iSCSI? This code is for SAS management Protocol. > > > > I gave that as an example of what the scsi standard says about negative > residual count return from the target. If SAS as sepecific and different > meaning to negative residual, it should be noted and handled. Please read the code first. If sas_smp_handler() returns a negative value, a lld doesn't transfer anything. The original code used full-residual. The original code is fine. Your 'this is a bug fix' claim is wrong. We need to revert the original behavior though.