On Tue, 2008-01-22 at 15:32 -0500, Jeff Garzik wrote:
> James Bottomley wrote:
> > Actually, I don't think it's a smaller I/O issue. The SMART protocol
> > specifically mandates that the transfers for SMART READ DATA and SMART
> > READ LOG shall be 512 bytes). However, the pio transfer routine does
> > seem to be assuming sector alignment as well, which will be where your
> > problems are coming from. I think we need to specify sector minimum
> > alignment for ata (but not atapi, which has its own non sector size pio
> > routine). How about the attached?
> >
> > We have to do this for all ATA devices, because they'll likely all
> > support SMART, and SMART is defined to be a PIO command.
> >
> > James
> >
> > ---
> >
> > diff --git a/drivers/ata/libata-scsi.c b/drivers/ata/libata-scsi.c
> > index 4bb268b..bc5cf6b 100644
> > --- a/drivers/ata/libata-scsi.c
> > +++ b/drivers/ata/libata-scsi.c
> > @@ -824,9 +824,6 @@ static void ata_scsi_sdev_config(struct scsi_device *sdev)
> > * requests.
> > */
> > sdev->max_device_blocked = 1;
> > -
> > - /* set the min alignment */
> > - blk_queue_update_dma_alignment(sdev->request_queue, ATA_DMA_PAD_SZ - 1);
> > }
> >
> > static void ata_scsi_dev_config(struct scsi_device *sdev,
> > @@ -842,7 +839,14 @@ static void ata_scsi_dev_config(struct scsi_device *sdev,
> > if (dev->class == ATA_DEV_ATAPI) {
> > struct request_queue *q = sdev->request_queue;
> > blk_queue_max_hw_segments(q, q->max_hw_segments - 1);
> > - }
> > +
> > + /* set the min alignment */
> > + blk_queue_update_dma_alignment(sdev->request_queue,
> > + ATA_DMA_PAD_SZ - 1);
> > + } else
> > + /* ATA devices must be sector aligned */
> > + blk_queue_update_dma_alignment(sdev->request_queue,
> > + ATA_SECT_SIZE - 1);
> >
> > if (dev->flags & ATA_DFLAG_AN)
> > set_bit(SDEV_EVT_MEDIA_CHANGE, sdev->supported_events);
>
>
> ACK
>
> Unlike ATAPI, ATA is indeed all 512-byte alignment transfers (_not_
> sector size, which may or may not be 512 bytes)
>
> Does this apply to libata? libata + jejb dma alignment patch?
>
> What tree...
It's scsi-misc-2.6; the blk_queue_update_dma_alignment() API doesn't
exist in mainline (yet).
James
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