On 01/26/2017 03:02 PM, Ram Pai wrote: > 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 <gpicc...@linux.vnet.ibm.com> >>>>>>>> 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.
Thanks Ram and Martin for the suggestion and explanation. I just sent a V3. Cheers, Guilherme > > RP > -- To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html