On Tue, 22 Jan 2008, James Bottomley wrote: > > --- 2.6.24-rc8-mm1/drivers/ata/libata-scsi.c 2008-01-17 16:49:47.000000000 +0000 > > +++ linux/drivers/ata/libata-scsi.c 2008-01-22 15:45:40.000000000 +0000 > > @@ -826,7 +826,7 @@ static void ata_scsi_sdev_config(struct > > sdev->max_device_blocked = 1; > > > > /* set the min alignment */ > > - blk_queue_update_dma_alignment(sdev->request_queue, ATA_DMA_PAD_SZ - 1); > > + blk_queue_update_dma_alignment(sdev->request_queue, ATA_SECT_SIZE - 1); > > } > > > > static void ata_scsi_dev_config(struct scsi_device *sdev, > > Unfortunately, that's likely not the entire hot fix ... the implication > is that we have some mapping error in the way we do direct SG_IO. Quite possibly, I'm not sure. > What the fix you propose does is make it far more likely that block will > copy, perform I/O then uncopy (almost certain, since most smartd data > transfers are well under ATA_SECT_SIZE, which is 512). However, > implicating a generic path like this implies that we would get the same > problem for SCSI commands as well, so the correct hot fix is below. I've not noticed any problems from the normal activity of the system, only from smartd's sg_ioctl. My impression was that it's a libata issue, because it's going through ata_pio_sector, which does ap->ops->data_xfer(qc->dev, buf + offset, qc->sect_size, do_write); referring to sect_size, without considering the possibility of any smaller I/O size. (Me, I don't even know why it's going PIO rather than DMA: I'm assuming smartd does things that way, but there's no limit to my ignorance here.) > However, I'd like to see if we can track the problem through the SG_IO > direct path ... how many adjacent page bytes are corrupt? Just a few or > a large number (I'm wondering if it's an off by one or off by alignment > type bug)? I've assumed it's just the one next page: because ata_pio_sector is doing a data_xfer of sect_size ATA_SECT_SIZE 512 to an offset above 0xe00 in the smartd stack page. The time I actually saw corruption rather than an oops at startup, it was in a tmpfs swap vector page running 64-bit kernel, and I didn't examine any further pages (just checked the page before and matched it up to smartd's stack, already suspecting that). I don't believe it's an off-by-one at your SCSI end. Hugh - To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
