swiotlb-xen: ensure we have a single callsite for xen_dma_map_page

Refactor the code a bit to make further changes easier.

Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

1 files changed, 16 insertions, 15 deletions

diff --git a/drivers/xen/swiotlb-xen.c b/drivers/xen/swiotlb-xen.c
index ba558094d0e6..64cb94dfedd4 100644
--- a/drivers/xen/swiotlb-xen.c
+++ b/drivers/xen/swiotlb-xen.c
@@ -388,13 +388,8 @@ static dma_addr_t xen_swiotlb_map_page(struct device *dev, struct page *page,
         if (dma_capable(dev, dev_addr, size) &&
             !range_straddles_page_boundary(phys, size) &&
                 !xen_arch_need_swiotlb(dev, phys, dev_addr) &&
-                (swiotlb_force != SWIOTLB_FORCE)) {
-                /* we are not interested in the dma_addr returned by
-                 * xen_dma_map_page, only in the potential cache flushes executed
-                 * by the function. */
-                xen_dma_map_page(dev, page, dev_addr, offset, size, dir, attrs);
-                return dev_addr;
-        }
+                swiotlb_force != SWIOTLB_FORCE)
+                goto done;
 
         /*
          * Oh well, have to allocate and map a bounce buffer.
@@ -407,19 +402,25 @@ static dma_addr_t xen_swiotlb_map_page(struct device *dev, struct page *page,
                 return DMA_MAPPING_ERROR;
 
         dev_addr = xen_phys_to_bus(map);
-        xen_dma_map_page(dev, pfn_to_page(map >> PAGE_SHIFT),
-                                        dev_addr, map & ~PAGE_MASK, size, dir, attrs);
 
         /*
          * Ensure that the address returned is DMA'ble
          */
-        if (dma_capable(dev, dev_addr, size))
-                return dev_addr;
-
-        attrs |= DMA_ATTR_SKIP_CPU_SYNC;
-        swiotlb_tbl_unmap_single(dev, map, size, dir, attrs);
+        if (unlikely(!dma_capable(dev, dev_addr, size))) {
+                swiotlb_tbl_unmap_single(dev, map, size, dir,
+                                attrs | DMA_ATTR_SKIP_CPU_SYNC);
+                return DMA_MAPPING_ERROR;
+        }
 
-        return DMA_MAPPING_ERROR;
+        page = pfn_to_page(map >> PAGE_SHIFT);
+        offset = map & ~PAGE_MASK;
+done:
+        /*
+         * we are not interested in the dma_addr returned by xen_dma_map_page,
+         * only in the potential cache flushes executed by the function.
+         */
+        xen_dma_map_page(dev, page, dev_addr, offset, size, dir, attrs);
+        return dev_addr;
 }
 
 /*