iommu/dma: Merge the CMA and alloc_pages allocation paths

Instead of having a separate code path for the non-blocking alloc_pages
and CMA allocations paths merge them into one.  There is a slight
behavior change here in that we try the page allocator if CMA fails.
This matches what dma-direct and other iommu drivers do and will be
needed to use the dma-iommu code on architectures without DMA remapping
later on.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Joerg Roedel <jroedel@suse.de>

drivers/iommu/dma-iommu.c

@@ -974,7 +974,7 @@ static void *iommu_dma_alloc(struct device *dev, size_t size,
 	bool coherent = dev_is_dma_coherent(dev);
 	int ioprot = dma_info_to_prot(DMA_BIDIRECTIONAL, coherent, attrs);
 	size_t iosize = size;
-	struct page *page;
+	struct page *page = NULL;
 	void *addr;
 
 	size = PAGE_ALIGN(size);
@@ -984,35 +984,26 @@ static void *iommu_dma_alloc(struct device *dev, size_t size,
 	    !(attrs & DMA_ATTR_FORCE_CONTIGUOUS))
 		return iommu_dma_alloc_remap(dev, iosize, handle, gfp, attrs);
 
-	if (!gfpflags_allow_blocking(gfp)) {
-		/*
-		 * In atomic context we can't remap anything, so we'll only
-		 * get the virtually contiguous buffer we need by way of a
-		 * physically contiguous allocation.
-		 */
-		if (coherent) {
-			page = alloc_pages(gfp, get_order(size));
-			addr = page ? page_address(page) : NULL;
-		} else {
+	if (!gfpflags_allow_blocking(gfp) && !coherent) {
 		addr = dma_alloc_from_pool(size, &page, gfp);
-		}
 		if (!addr)
 			return NULL;
 
 		*handle = __iommu_dma_map(dev, page_to_phys(page), iosize,
 					  ioprot);
 		if (*handle == DMA_MAPPING_ERROR) {
-			if (coherent)
-				__free_pages(page, get_order(size));
-			else
 			dma_free_from_pool(addr, size);
 			return NULL;
 		}
 		return addr;
 	}
 
+	if (gfpflags_allow_blocking(gfp))
 		page = dma_alloc_from_contiguous(dev, size >> PAGE_SHIFT,
-					 get_order(size), gfp & __GFP_NOWARN);
+						 get_order(size),
+						 gfp & __GFP_NOWARN);
+	if (!page)
+		page = alloc_pages(gfp, get_order(size));
 	if (!page)
 		return NULL;
 
@@ -1038,7 +1029,8 @@ static void *iommu_dma_alloc(struct device *dev, size_t size,
 out_unmap:
 	__iommu_dma_unmap(dev, *handle, iosize);
 out_free_pages:
-	dma_release_from_contiguous(dev, page, size >> PAGE_SHIFT);
+	if (!dma_release_from_contiguous(dev, page, size >> PAGE_SHIFT))
+		__free_pages(page, get_order(size));
 	return NULL;
 }