libata: fix dma_unmap_sg misuse

libata passes the returned value of dma_map_sg() to
dma_unmap_sg(),which is the misuse of dma_unmap_sg().

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.

Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Acked-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>
Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>

1 files changed, 2 insertions, 2 deletions

diff --git a/drivers/ata/libata-core.c b/drivers/ata/libata-core.c
index 9fbf0595f3d4..5e324cea3019 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;