From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Guilherme G. Piccoli" Subject: Re: [PATCH v2] mpt3sas: Force request partial completion alignment Date: Thu, 26 Jan 2017 11:31:53 -0200 Message-ID: <5889FA49.4030802@linux.vnet.ibm.com> References: <1485272838-23180-1-git-send-email-gpiccoli@linux.vnet.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Return-path: Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]:46364 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752049AbdAZNcF (ORCPT ); Thu, 26 Jan 2017 08:32:05 -0500 Received: from pps.filterd (m0098409.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.20/8.16.0.20) with SMTP id v0QDT45D097461 for ; Thu, 26 Jan 2017 08:32:04 -0500 Received: from e24smtp01.br.ibm.com (e24smtp01.br.ibm.com [32.104.18.85]) by mx0a-001b2d01.pphosted.com with ESMTP id 286xt4ssue-1 (version=TLSv1.2 cipher=AES256-SHA bits=256 verify=NOT) for ; Thu, 26 Jan 2017 08:32:04 -0500 Received: from localhost by e24smtp01.br.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Thu, 26 Jan 2017 11:32:01 -0200 Received: from d24relay04.br.ibm.com (d24relay04.br.ibm.com [9.18.232.146]) by d24dlp01.br.ibm.com (Postfix) with ESMTP id B68733520068 for ; Thu, 26 Jan 2017 08:31:26 -0500 (EST) Received: from d24av05.br.ibm.com (d24av05.br.ibm.com [9.18.232.44]) by d24relay04.br.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id v0QDVx8j21626908 for ; Thu, 26 Jan 2017 11:31:59 -0200 Received: from d24av05.br.ibm.com (localhost [127.0.0.1]) by d24av05.br.ibm.com (8.14.4/8.14.4/NCO v10.0 AVout) with ESMTP id v0QDVwx6007527 for ; Thu, 26 Jan 2017 11:31:59 -0200 In-Reply-To: Sender: linux-scsi-owner@vger.kernel.org List-Id: linux-scsi@vger.kernel.org To: "Martin K. Petersen" Cc: 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, linuxram@us.ibm.com 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. Let me know your thoughts. Thanks, Guilherme