Index: sys/compat/linuxkpi/common/include/linux/scatterlist.h
===================================================================
--- sys/compat/linuxkpi/common/include/linux/scatterlist.h
+++ sys/compat/linuxkpi/common/include/linux/scatterlist.h
@@ -44,7 +44,6 @@
 	unsigned int offset;
 	unsigned int length;
 	dma_addr_t dma_address;
-	unsigned int dma_length;
 };
 
 CTASSERT((sizeof(struct scatterlist) & SG_PAGE_LINK_MASK) == 0);
@@ -79,7 +78,7 @@
 	((struct scatterlist *) ((sg)->page_link & ~SG_PAGE_LINK_MASK))
 
 #define	sg_dma_address(sg)	(sg)->dma_address
-#define	sg_dma_len(sg)		(sg)->dma_length
+#define	sg_dma_len(sg)		(sg)->length
 
 #define	for_each_sg_page(sgl, iter, nents, pgoffset)			\
 	for (_sg_iter_init(sgl, iter, nents, pgoffset);			\
Index: sys/compat/linuxkpi/common/src/linux_pci.c
===================================================================
--- sys/compat/linuxkpi/common/src/linux_pci.c
+++ sys/compat/linuxkpi/common/src/linux_pci.c
@@ -492,6 +492,7 @@
 {
 	struct linux_dma_priv *priv;
 	struct linux_dma_obj *obj;
+	struct linux_dma_obj *old;
 	int error, nseg;
 	bus_dma_segment_t seg;
 
@@ -518,6 +519,16 @@
 	KASSERT(++nseg == 1, ("More than one segment (nseg=%d)", nseg));
 	obj->dma_addr = seg.ds_addr;
 
+	/* check if there is an existing mapping and remove it */
+	old = LINUX_DMA_PCTRIE_LOOKUP(&priv->ptree, obj->dma_addr);
+	if (old != NULL) {
+		LINUX_DMA_PCTRIE_REMOVE(&priv->ptree, obj->dma_addr);
+		bus_dmamap_unload(priv->dmat, old->dmamap);
+		bus_dmamap_destroy(priv->dmat, old->dmamap);
+		uma_zfree(linux_dma_obj_zone, old);
+	}
+
+	/* insert new mapping */
 	error = LINUX_DMA_PCTRIE_INSERT(&priv->ptree, obj);
 	if (error != 0) {
 		bus_dmamap_unload(priv->dmat, obj->dmamap);
@@ -558,10 +569,9 @@
 {
 	struct linux_dma_priv *priv;
 	struct linux_dma_obj *obj;
-	struct scatterlist *dma_sg, *sg;
-	int dma_nents, error, nseg;
-	size_t seg_len;
-	vm_paddr_t seg_phys, prev_phys_end;
+	struct linux_dma_obj *old;
+	struct scatterlist *sg;
+	int error, i, nseg;
 	bus_dma_segment_t seg;
 
 	priv = dev->dma_priv;
@@ -575,24 +585,10 @@
 		return (0);
 	}
 
-	sg = sgl;
-	dma_sg = sg;
-	dma_nents = 0;
-
-	while (nents > 0) {
-		seg_phys = sg_phys(sg);
-		seg_len = sg->length;
-		while (--nents > 0) {
-			prev_phys_end = sg_phys(sg) + sg->length;
-			sg = sg_next(sg);
-			if (prev_phys_end != sg_phys(sg))
-				break;
-			seg_len += sg->length;
-		}
-
+	for_each_sg(sgl, sg, nents, i) {
 		nseg = -1;
 		if (_bus_dmamap_load_phys(priv->dmat, obj->dmamap,
-		    seg_phys, seg_len, BUS_DMA_NOWAIT,
+		    sg_phys(sg), sg->length, BUS_DMA_NOWAIT,
 		    &seg, &nseg) != 0) {
 			bus_dmamap_unload(priv->dmat, obj->dmamap);
 			bus_dmamap_destroy(priv->dmat, obj->dmamap);
@@ -601,16 +597,21 @@
 			return (0);
 		}
 		KASSERT(++nseg == 1, ("More than one segment (nseg=%d)", nseg));
+		sg_dma_address(sg) = seg.ds_addr;
+	}
 
-		sg_dma_address(dma_sg) = seg.ds_addr;
-		sg_dma_len(dma_sg) = seg.ds_len;
+	obj->dma_addr = sg_dma_address(sgl);
 
-		dma_sg = sg_next(dma_sg);
-		dma_nents++;
-        }
+	/* check if there is an existing mapping and remove it */
+	old = LINUX_DMA_PCTRIE_LOOKUP(&priv->ptree, obj->dma_addr);
+	if (old != NULL) {
+		LINUX_DMA_PCTRIE_REMOVE(&priv->ptree, obj->dma_addr);
+		bus_dmamap_unload(priv->dmat, old->dmamap);
+		bus_dmamap_destroy(priv->dmat, old->dmamap);
+		uma_zfree(linux_dma_obj_zone, old);
+	}
 
-	obj->dma_addr = sg_dma_address(sgl);
-
+	/* insert new mapping */
 	error = LINUX_DMA_PCTRIE_INSERT(&priv->ptree, obj);
 	if (error != 0) {
 		bus_dmamap_unload(priv->dmat, obj->dmamap);
@@ -620,7 +621,7 @@
 		return (0);
 	}
 	DMA_PRIV_UNLOCK(priv);
-	return (dma_nents);
+	return (nents);
 }
 
 void