iommu/dma: Refactor iommu_dma_alloc, part 2

All the logic in iommu_dma_alloc that deals with page allocation from
the CMA or page allocators can be split into a self-contained helper,
and we can than map the result of that or the atomic pool allocation
with the iommu later.  This also allows reusing __iommu_dma_free to
tear down the allocations and MMU mappings when the IOMMU mapping
fails.

Based on a patch from Robin Murphy.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Joerg Roedel <jroedel@suse.de>

drivers/iommu/dma-iommu.c

@@ -972,35 +972,14 @@ static void iommu_dma_free(struct device *dev, size_t size, void *cpu_addr,
 	__iommu_dma_free(dev, size, cpu_addr);
 }
 
-static void *iommu_dma_alloc(struct device *dev, size_t size,
-		dma_addr_t *handle, gfp_t gfp, unsigned long attrs)
+static void *iommu_dma_alloc_pages(struct device *dev, size_t size,
+		struct page **pagep, gfp_t gfp, unsigned long attrs)
 {
 	bool coherent = dev_is_dma_coherent(dev);
-	int ioprot = dma_info_to_prot(DMA_BIDIRECTIONAL, coherent, attrs);
 	size_t alloc_size = PAGE_ALIGN(size);
 	struct page *page = NULL;
 	void *cpu_addr;
 
-	gfp |= __GFP_ZERO;
-
-	if (gfpflags_allow_blocking(gfp) &&
-	    !(attrs & DMA_ATTR_FORCE_CONTIGUOUS))
-		return iommu_dma_alloc_remap(dev, size, handle, gfp, attrs);
-
-	if (!gfpflags_allow_blocking(gfp) && !coherent) {
-		cpu_addr = dma_alloc_from_pool(alloc_size, &page, gfp);
-		if (!cpu_addr)
-			return NULL;
-
-		*handle = __iommu_dma_map(dev, page_to_phys(page), size,
-					  ioprot);
-		if (*handle == DMA_MAPPING_ERROR) {
-			dma_free_from_pool(cpu_addr, alloc_size);
-			return NULL;
-		}
-		return cpu_addr;
-	}
-
 	if (gfpflags_allow_blocking(gfp))
 		page = dma_alloc_from_contiguous(dev, alloc_size >> PAGE_SHIFT,
 						 get_order(alloc_size),
@@ -1010,33 +989,59 @@ static void *iommu_dma_alloc(struct device *dev, size_t size,
 	if (!page)
 		return NULL;
 
-	*handle = __iommu_dma_map(dev, page_to_phys(page), size, ioprot);
-	if (*handle == DMA_MAPPING_ERROR)
-		goto out_free_pages;
-
 	if (!coherent || PageHighMem(page)) {
 		pgprot_t prot = arch_dma_mmap_pgprot(dev, PAGE_KERNEL, attrs);
 
 		cpu_addr = dma_common_contiguous_remap(page, alloc_size,
 				VM_USERMAP, prot, __builtin_return_address(0));
 		if (!cpu_addr)
-			goto out_unmap;
+			goto out_free_pages;
 
 		if (!coherent)
 			arch_dma_prep_coherent(page, size);
 	} else {
 		cpu_addr = page_address(page);
 	}
+
+	*pagep = page;
 	memset(cpu_addr, 0, alloc_size);
 	return cpu_addr;
-out_unmap:
-	__iommu_dma_unmap(dev, *handle, size);
 out_free_pages:
 	if (!dma_release_from_contiguous(dev, page, alloc_size >> PAGE_SHIFT))
 		__free_pages(page, get_order(alloc_size));
 	return NULL;
 }
 
+static void *iommu_dma_alloc(struct device *dev, size_t size,
+		dma_addr_t *handle, gfp_t gfp, unsigned long attrs)
+{
+	bool coherent = dev_is_dma_coherent(dev);
+	int ioprot = dma_info_to_prot(DMA_BIDIRECTIONAL, coherent, attrs);
+	struct page *page = NULL;
+	void *cpu_addr;
+
+	gfp |= __GFP_ZERO;
+
+	if (gfpflags_allow_blocking(gfp) &&
+	    !(attrs & DMA_ATTR_FORCE_CONTIGUOUS))
+		return iommu_dma_alloc_remap(dev, size, handle, gfp, attrs);
+
+	if (!gfpflags_allow_blocking(gfp) && !coherent)
+		cpu_addr = dma_alloc_from_pool(PAGE_ALIGN(size), &page, gfp);
+	else
+		cpu_addr = iommu_dma_alloc_pages(dev, size, &page, gfp, attrs);
+	if (!cpu_addr)
+		return NULL;
+
+	*handle = __iommu_dma_map(dev, page_to_phys(page), size, ioprot);
+	if (*handle == DMA_MAPPING_ERROR) {
+		__iommu_dma_free(dev, size, cpu_addr);
+		return NULL;
+	}
+
+	return cpu_addr;
+}
+
 static int __iommu_dma_mmap_pfn(struct vm_area_struct *vma,
 			      unsigned long pfn, size_t size)
 {