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 00:16:39 +0900 Message-ID: <20090513001756P.fujita.tomonori@lab.ntt.co.jp> References: <20090511235852Z.fujita.tomonori@lab.ntt.co.jp> <4A093A34.3020101@panasas.com> <20090513000150H.fujita.tomonori@lab.ntt.co.jp> 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]:49645 "EHLO sh.osrg.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755972AbZELPVS (ORCPT ); Tue, 12 May 2009 11:21:18 -0400 In-Reply-To: <20090513000150H.fujita.tomonori@lab.ntt.co.jp> Sender: linux-ide-owner@vger.kernel.org List-Id: linux-ide@vger.kernel.org To: bharrosh@panasas.com Cc: 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 Wed, 13 May 2009 00:00:47 +0900 FUJITA Tomonori wrote: > 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 Oops, smp_execute_task() > 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. Note that you could claim that we should handle residual here when you find SAS_DATA_OVERRUN in smp_execute_task(). I guess that it means INVALID_REQUEST_FRAME_LENGTH; the driver sent the data and doesn't get anything. So we could do better about residual for the error but I didn't know about the lld spec and I kept the code that the vendor submitted.