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;
 
diff --git a/include/linux/libata.h b/include/linux/libata.h
index dd818c7decd7..fbf064e13ad5 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;