x86: fix nommu_alloc_coherent allocation with NULL device argument

We need to use __GFP_DMA for NULL device argument (fallback_dev) with
pci-nommu. It's a hack for ISA (and some old code) so we need to use
GFP_DMA.
Signed-off-by: NFUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Acked-by: NJoerg Roedel <joerg.roedel@amd.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

arch/x86/kernel/pci-nommu.c

@@ -80,7 +80,6 @@ nommu_alloc_coherent(struct device *hwdev, size_t size,
 	int node;
 	struct page *page;
 
-	gfp &= ~(__GFP_DMA | __GFP_HIGHMEM | __GFP_DMA32);
 	gfp |= __GFP_ZERO;
 
 	dma_mask = hwdev->coherent_dma_mask;
@@ -93,7 +92,7 @@ nommu_alloc_coherent(struct device *hwdev, size_t size,
 	node = dev_to_node(hwdev);
 
 #ifdef CONFIG_X86_64
-	if (dma_mask <= DMA_32BIT_MASK)
+	if (dma_mask <= DMA_32BIT_MASK && !(gfp & GFP_DMA))
 		gfp |= GFP_DMA32;
 #endif
 

include/asm-x86/dma-mapping.h

@@ -246,6 +246,8 @@ dma_alloc_coherent(struct device *dev, size_t size, dma_addr_t *dma_handle,
 	struct dma_mapping_ops *ops = get_dma_ops(dev);
 	void *memory;
 
+	gfp &= ~(__GFP_DMA | __GFP_HIGHMEM | __GFP_DMA32);
+
 	if (dma_alloc_from_coherent(dev, size, dma_handle, &memory))
 		return memory;