From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ram Pai Subject: Re: [PATCH v2] mpt3sas: Force request partial completion alignment Date: Thu, 26 Jan 2017 09:02:34 -0800 Message-ID: <20170126170234.GD5657@ram.oc3035372033.ibm.com> References: <1485272838-23180-1-git-send-email-gpiccoli@linux.vnet.ibm.com> <5889FA49.4030802@linux.vnet.ibm.com> Reply-To: Ram Pai Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]:46852 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752479AbdAZRCw (ORCPT ); Thu, 26 Jan 2017 12:02:52 -0500 Received: from pps.filterd (m0098404.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.20/8.16.0.20) with SMTP id v0QGwbOl010684 for ; Thu, 26 Jan 2017 12:02:47 -0500 Received: from e18.ny.us.ibm.com (e18.ny.us.ibm.com [129.33.205.208]) by mx0a-001b2d01.pphosted.com with ESMTP id 287jhk81mr-1 (version=TLSv1.2 cipher=AES256-SHA bits=256 verify=NOT) for ; Thu, 26 Jan 2017 12:02:46 -0500 Received: from localhost by e18.ny.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Thu, 26 Jan 2017 12:02:45 -0500 Content-Disposition: inline In-Reply-To: <5889FA49.4030802@linux.vnet.ibm.com> Sender: linux-scsi-owner@vger.kernel.org List-Id: linux-scsi@vger.kernel.org To: "Guilherme G. Piccoli" Cc: "Martin K. Petersen" , linux-scsi@vger.kernel.org, MPT-FusionLinux.pdl@broadcom.com, sathya.prakash@broadcom.com, chaitra.basappa@broadcom.com, suganath-prabu.subramani@broadcom.com, sreekanth.reddy@broadcom.com, brking@linux.vnet.ibm.com, mauricfo@linux.vnet.ibm.com On Thu, Jan 26, 2017 at 11:31:53AM -0200, Guilherme G. Piccoli wrote: > On 01/25/2017 09:46 PM, Martin K. Petersen wrote: > >>>>>> "Guilherme" == Guilherme G Piccoli writes: > > > > Hi Guilherme, > > Hi Martin, thanks for the review! > > > > > > diff --git a/drivers/scsi/mpt3sas/mpt3sas_scsih.c b/drivers/scsi/mpt3sas/mpt3sas_scsih.c > > index 75f3fce..e52c942 100644 > > --- a/drivers/scsi/mpt3sas/mpt3sas_scsih.c > > +++ b/drivers/scsi/mpt3sas/mpt3sas_scsih.c > > @@ -4657,6 +4657,8 @@ _scsih_io_done(struct MPT3SAS_ADAPTER *ioc, u16 smid, u8 msix_index, u32 reply) > > struct MPT3SAS_DEVICE *sas_device_priv_data; > > u32 response_code = 0; > > unsigned long flags; > > + unsigned int sector_sz; > > + struct request *req; > > > > mpi_reply = mpt3sas_base_get_reply_virt_addr(ioc, reply); > > scmd = _scsih_scsi_lookup_get_clear(ioc, smid); > > @@ -4715,6 +4717,21 @@ _scsih_io_done(struct MPT3SAS_ADAPTER *ioc, u16 smid, u8 msix_index, u32 reply) > > } > > > > xfer_cnt = le32_to_cpu(mpi_reply->TransferCount); > > + > > + /* In case of bogus fw or device, we could end up having > > + * unaligned partial completion. We can force alignment here, > > + * then scsi-ml does not need to handle this misbehavior. > > + */ > > + sector_sz = scmd->device->sector_size; > > + req = scmd->request; > > + if (unlikely(sector_sz && req && (req->cmd_type == REQ_TYPE_FS) && > > + (xfer_cnt % sector_sz))) { > > > > Maybe a bit zealous on the sanity checking... > > A bit...? heheh > Too much I'd say. Since this is dealing with a bogus FW scenario, I > found more safe to check everything...of course we can remove checks if > it's sure req isn't NULL ever. The sector_sz check is avoiding > degenerate cases, since our division below. > > > > > > + sdev_printk(KERN_INFO, scmd->device, > > + "unaligned partial completion avoided (xfer_cnt=%u, sector_sz=%u)\n", > > + xfer_cnt, sector_sz); > > + xfer_cnt = (xfer_cnt / sector_sz) * sector_sz; > > > > Not so keen on divisions. xfer_cnt = round_down(xfer_cnt, sector_sz), maybe? > > > > Martin, I might be completely wrong here (please correct me if this is > the case), but isn't C standard integer division a truncation that acts > like a round down? I checked (what I think is) the specification of C > language (ISO/IEC 9899:1999), and it seems the division proposed by Ram > Pai is accurate in this case. Also, both variables are unsigned. Guilherme, Its better to use round_down() instead of division. Among other things it saves a few nanoseconds. RP