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 <gpiccoli@xxxxxxxxxxxxxxxxxx> 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
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