Re: [PATCH v2] mpt3sas: Force request partial completion alignment

[Sreekanth Reddy <sreekanth.reddy@broadcom.com>]

On Tue, Jan 24, 2017 at 9:17 PM, Guilherme G. Piccoli
<gpiccoli@linux.vnet.ibm.com> wrote:
> From: Ram Pai <linuxram@us.ibm.com>
>
> The firmware or device, possibly under a heavy I/O load, can return
> on a partial unaligned boundary. Scsi-ml expects these requests to be
> completed on an alignment boundary. Scsi-ml blindly requeues the I/O
> without checking the alignment boundary of the I/O request for the
> remaining bytes. This leads to errors, since devices cannot perform
> non-aligned read/write operations.
>
> This patch fixes the issue in the driver. It aligns unaligned
> completions of FS requests, by truncating them to the nearest
> alignment boundary.
>
> Reported-by: Mauricio Faria De Oliveira <mauricfo@linux.vnet.ibm.com>
> Signed-off-by: Guilherme G. Piccoli <gpiccoli@linux.vnet.ibm.com>
> Signed-off-by: Ram Pai <linuxram@us.ibm.com>
> ---
> v1->v2:
>   * Improved printk, by showing some variables too [suggested by Sreekanth].

This patch looks good. Please consider this patch as

Acked-by: Sreekanth Reddy <Sreekanth.Reddy@broadcom.com>

>
>  drivers/scsi/mpt3sas/mpt3sas_scsih.c | 17 +++++++++++++++++
>  1 file changed, 17 insertions(+)
>
> 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))) {
> +               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;
> +       }
> +
>         scsi_set_resid(scmd, scsi_bufflen(scmd) - xfer_cnt);
>         if (ioc_status & MPI2_IOCSTATUS_FLAG_LOG_INFO_AVAILABLE)
>                 log_info =  le32_to_cpu(mpi_reply->IOCLogInfo);
> --
> 2.1.0
>