swiotlb: sg chaining support

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

lib/swiotlb.c

@@ -677,16 +677,17 @@ swiotlb_sync_single_range_for_device(struct device *hwdev, dma_addr_t dev_addr,
  * same here.
  */
 int
-swiotlb_map_sg(struct device *hwdev, struct scatterlist *sg, int nelems,
+swiotlb_map_sg(struct device *hwdev, struct scatterlist *sgl, int nelems,
 	       int dir)
 {
+	struct scatterlist *sg;
 	void *addr;
 	dma_addr_t dev_addr;
 	int i;
 
 	BUG_ON(dir == DMA_NONE);
 
-	for (i = 0; i < nelems; i++, sg++) {
+	for_each_sg(sgl, sg, nelems, i) {
 		addr = SG_ENT_VIRT_ADDRESS(sg);
 		dev_addr = virt_to_bus(addr);
 		if (swiotlb_force || address_needs_mapping(hwdev, dev_addr)) {
@@ -696,7 +697,7 @@ swiotlb_map_sg(struct device *hwdev, struct scatterlist *sg, int nelems,
 				   to do proper error handling. */
 				swiotlb_full(hwdev, sg->length, dir, 0);
 				swiotlb_unmap_sg(hwdev, sg - i, i, dir);
-				sg[0].dma_length = 0;
+				sgl[0].dma_length = 0;
 				return 0;
 			}
 			sg->dma_address = virt_to_bus(map);
@@ -712,19 +713,21 @@ swiotlb_map_sg(struct device *hwdev, struct scatterlist *sg, int nelems,
  * concerning calls here are the same as for swiotlb_unmap_single() above.
  */
 void
-swiotlb_unmap_sg(struct device *hwdev, struct scatterlist *sg, int nelems,
+swiotlb_unmap_sg(struct device *hwdev, struct scatterlist *sgl, int nelems,
 		 int dir)
 {
+	struct scatterlist *sg;
 	int i;
 
 	BUG_ON(dir == DMA_NONE);
 
-	for (i = 0; i < nelems; i++, sg++)
+	for_each_sg(sgl, sg, nelems, i) {
 		if (sg->dma_address != SG_ENT_PHYS_ADDRESS(sg))
 			unmap_single(hwdev, bus_to_virt(sg->dma_address),
 				     sg->dma_length, dir);
 		else if (dir == DMA_FROM_DEVICE)
 			dma_mark_clean(SG_ENT_VIRT_ADDRESS(sg), sg->dma_length);
+	}
 }
 
 /*
@@ -735,19 +738,21 @@ swiotlb_unmap_sg(struct device *hwdev, struct scatterlist *sg, int nelems,
  * and usage.
  */
 static void
-swiotlb_sync_sg(struct device *hwdev, struct scatterlist *sg,
+swiotlb_sync_sg(struct device *hwdev, struct scatterlist *sgl,
 		int nelems, int dir, int target)
 {
+	struct scatterlist *sg;
 	int i;
 
 	BUG_ON(dir == DMA_NONE);
 
-	for (i = 0; i < nelems; i++, sg++)
+	for_each_sg(sgl, sg, nelems, i) {
 		if (sg->dma_address != SG_ENT_PHYS_ADDRESS(sg))
 			sync_single(hwdev, bus_to_virt(sg->dma_address),
 				    sg->dma_length, dir, target);
 		else if (dir == DMA_FROM_DEVICE)
 			dma_mark_clean(SG_ENT_VIRT_ADDRESS(sg), sg->dma_length);
+	}
 }
 
 void