[Xen-devel] [PATCH 4/4] swiotlb-xen: ensure we have a single callsite for xen_dma_map_page

[Christoph Hellwig <hch@xxxxxx>]

Refactor the code a bit to make further changes easier.

Signed-off-by: Christoph Hellwig <hch@xxxxxx>
---
 drivers/xen/swiotlb-xen.c | 31 ++++++++++++++++---------------
 1 file changed, 16 insertions(+), 15 deletions(-)

diff --git a/drivers/xen/swiotlb-xen.c b/drivers/xen/swiotlb-xen.c
index 9a951504dc12..5dcb06fe9667 100644
--- a/drivers/xen/swiotlb-xen.c
+++ b/drivers/xen/swiotlb-xen.c
@@ -391,13 +391,8 @@ 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.
@@ -410,19 +405,25 @@ 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;
 }
 
 /*
-- 
2.20.1


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