On Tuesday 17 February 2009, FUJITA Tomonori wrote:
> Looks like that libata misuses dma_unmap_sg though I'm not familiar
> with libata so I might completely misunderstand something.
>
> =
> From: FUJITA Tomonori <fujita.tomonori@xxxxxxxxxxxxx>
> Subject: [PATCH] fix dma_unmap_sg misuse
>
> DMA-mapping.txt says:
>
> To unmap a scatterlist, just call:
>
> pci_unmap_sg(pdev, sglist, nents, direction);
>
> Again, make sure DMA activity has already finished.
>
> PLEASE NOTE: The 'nents' argument to the pci_unmap_sg call must be
> the _same_ one you passed into the pci_map_sg call,
> it should _NOT_ be the 'count' value _returned_ from the
> pci_map_sg call.
This is correct and other subsystems (SCSI, IDE) are compliant with it.
> Signed-off-by: FUJITA Tomonori <fujita.tomonori@xxxxxxxxxxxxx>
Acked-by: Bartlomiej Zolnierkiewicz <bzolnier@xxxxxxxxx>
> ---
> drivers/ata/libata-core.c | 4 ++--
> include/linux/libata.h | 1 +
> 2 files changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/ata/libata-core.c b/drivers/ata/libata-core.c
> index 9fbf059..5e324ce 100644
> --- a/drivers/ata/libata-core.c
> +++ b/drivers/ata/libata-core.c
> @@ -4612,7 +4612,7 @@ void ata_sg_clean(struct ata_queued_cmd *qc)
> VPRINTK("unmapping %u sg elements\n", qc->n_elem);
>
> if (qc->n_elem)
> - dma_unmap_sg(ap->dev, sg, qc->n_elem, dir);
> + dma_unmap_sg(ap->dev, sg, qc->orig_n_elem, dir);
>
> qc->flags &= ~ATA_QCFLAG_DMAMAP;
> qc->sg = NULL;
> @@ -4727,7 +4727,7 @@ static int ata_sg_setup(struct ata_queued_cmd *qc)
> return -1;
>
> DPRINTK("%d sg elements mapped\n", n_elem);
> -
> + qc->orig_n_elem = qc->n_elem;
> qc->n_elem = n_elem;
> qc->flags |= ATA_QCFLAG_DMAMAP;
>
> diff --git a/include/linux/libata.h b/include/linux/libata.h
> index 5577ea8..2de827d 100644
> --- a/include/linux/libata.h
> +++ b/include/linux/libata.h
> @@ -530,6 +530,7 @@ struct ata_queued_cmd {
> unsigned long flags; /* ATA_QCFLAG_xxx */
> unsigned int tag;
> unsigned int n_elem;
> + unsigned int orig_n_elem;
>
> int dma_dir;
--
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