swiotlb: move orig addr and size validation into swiotlb_bounce

Move the code to find and validate the original buffer address and size
from the callers into swiotlb_bounce.  This means a tiny bit of extra
work in the swiotlb_map path, but avoids code duplication and a leads to
a better code structure.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

kernel/dma/swiotlb.c

@@ -460,12 +460,25 @@ void __init swiotlb_exit(void)
 /*
  * Bounce: copy the swiotlb buffer from or back to the original dma location
  */
-static void swiotlb_bounce(phys_addr_t orig_addr, phys_addr_t tlb_addr,
-			   size_t size, enum dma_data_direction dir)
+static void swiotlb_bounce(struct device *dev, phys_addr_t tlb_addr, size_t size,
+			   enum dma_data_direction dir)
 {
+	int index = (tlb_addr - io_tlb_start) >> IO_TLB_SHIFT;
+	size_t alloc_size = io_tlb_alloc_size[index];
+	phys_addr_t orig_addr = io_tlb_orig_addr[index];
 	unsigned long pfn = PFN_DOWN(orig_addr);
 	unsigned char *vaddr = phys_to_virt(tlb_addr);
 
+	if (orig_addr == INVALID_PHYS_ADDR)
+		return;
+
+	if (size > alloc_size) {
+		dev_WARN_ONCE(dev, 1,
+			"Buffer overflow detected. Allocation size: %zu. Mapping size: %zu.\n",
+			alloc_size, size);
+		size = alloc_size;
+	}
+
 	if (PageHighMem(pfn_to_page(pfn))) {
 		/* The buffer does not have a mapping.  Map it in and copy */
 		unsigned int offset = orig_addr & ~PAGE_MASK;
@@ -644,21 +657,10 @@ phys_addr_t swiotlb_tbl_map_single(struct device *dev, phys_addr_t orig_addr,
 	tlb_addr = slot_addr(io_tlb_start, index) + offset;
 	if (!(attrs & DMA_ATTR_SKIP_CPU_SYNC) &&
 	    (dir == DMA_TO_DEVICE || dir == DMA_BIDIRECTIONAL))
-		swiotlb_bounce(orig_addr, tlb_addr, mapping_size, DMA_TO_DEVICE);
+		swiotlb_bounce(dev, tlb_addr, mapping_size, DMA_TO_DEVICE);
 	return tlb_addr;
 }
 
-static void validate_sync_size_and_truncate(struct device *hwdev, size_t alloc_size, size_t *size)
-{
-	if (*size > alloc_size) {
-		/* Warn and truncate mapping_size */
-		dev_WARN_ONCE(hwdev, 1,
-			"Attempt for buffer overflow. Original size: %zu. Mapping size: %zu.\n",
-			alloc_size, *size);
-		*size = alloc_size;
-	}
-}
-
 /*
  * tlb_addr is the physical address of the bounce buffer to unmap.
  */
@@ -669,19 +671,15 @@ void swiotlb_tbl_unmap_single(struct device *hwdev, phys_addr_t tlb_addr,
 	unsigned long flags;
 	unsigned int offset = swiotlb_align_offset(hwdev, tlb_addr);
 	int index = (tlb_addr - offset - io_tlb_start) >> IO_TLB_SHIFT;
-	phys_addr_t orig_addr = io_tlb_orig_addr[index];
-	size_t alloc_size = io_tlb_alloc_size[index];
-	int i, count, nslots = nr_slots(alloc_size + offset);
-
-	validate_sync_size_and_truncate(hwdev, alloc_size, &mapping_size);
+	int nslots = nr_slots(io_tlb_alloc_size[index] + offset);
+	int count, i;
 
 	/*
 	 * First, sync the memory before unmapping the entry
 	 */
-	if (orig_addr != INVALID_PHYS_ADDR &&
-	    !(attrs & DMA_ATTR_SKIP_CPU_SYNC) &&
-	    ((dir == DMA_FROM_DEVICE) || (dir == DMA_BIDIRECTIONAL)))
-		swiotlb_bounce(orig_addr, tlb_addr, mapping_size, DMA_FROM_DEVICE);
+	if (!(attrs & DMA_ATTR_SKIP_CPU_SYNC) &&
+	    (dir == DMA_FROM_DEVICE || dir == DMA_BIDIRECTIONAL))
+		swiotlb_bounce(hwdev, tlb_addr, mapping_size, DMA_FROM_DEVICE);
 
 	/*
 	 * Return the buffer to the free list by setting the corresponding
@@ -721,27 +719,16 @@ void swiotlb_tbl_sync_single(struct device *hwdev, phys_addr_t tlb_addr,
 			     size_t size, enum dma_data_direction dir,
 			     enum dma_sync_target target)
 {
-	int index = (tlb_addr - io_tlb_start) >> IO_TLB_SHIFT;
-	size_t alloc_size = io_tlb_alloc_size[index];
-	phys_addr_t orig_addr = io_tlb_orig_addr[index];
-
-	if (orig_addr == INVALID_PHYS_ADDR)
-		return;
-
-	validate_sync_size_and_truncate(hwdev, alloc_size, &size);
-
 	switch (target) {
 	case SYNC_FOR_CPU:
 		if (likely(dir == DMA_FROM_DEVICE || dir == DMA_BIDIRECTIONAL))
-			swiotlb_bounce(orig_addr, tlb_addr,
-				       size, DMA_FROM_DEVICE);
+			swiotlb_bounce(hwdev, tlb_addr, size, DMA_FROM_DEVICE);
 		else
 			BUG_ON(dir != DMA_TO_DEVICE);
 		break;
 	case SYNC_FOR_DEVICE:
 		if (likely(dir == DMA_TO_DEVICE || dir == DMA_BIDIRECTIONAL))
-			swiotlb_bounce(orig_addr, tlb_addr,
-				       size, DMA_TO_DEVICE);
+			swiotlb_bounce(hwdev, tlb_addr, size, DMA_TO_DEVICE);
 		else
 			BUG_ON(dir != DMA_FROM_DEVICE);
 		break;