arch/x86/kernel/pci-dma.c: fix dma_generic_alloc_coherent() when CONFIG_DMA_CMA is enabled

dma_generic_alloc_coherent() firstly attempts to allocate by
dma_alloc_from_contiguous() if CONFIG_DMA_CMA is enabled.  But the
memory region allocated by it may not fit within the device's DMA mask.
This change makes it fall back to usual alloc_pages_node() allocation
for such cases.
Signed-off-by: NAkinobu Mita <akinobu.mita@gmail.com>
Cc: Marek Szyprowski <m.szyprowski@samsung.com>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: Don Dutile <ddutile@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Andi Kleen <andi@firstfloor.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

arch/x86/kernel/pci-dma.c

@@ -101,8 +101,13 @@ void *dma_generic_alloc_coherent(struct device *dev, size_t size,
 again:
 	page = NULL;
 	/* CMA can be used only in the context which permits sleeping */
-	if (flag & __GFP_WAIT)
+	if (flag & __GFP_WAIT) {
 		page = dma_alloc_from_contiguous(dev, count, get_order(size));
+		if (page && page_to_phys(page) + size > dma_mask) {
+			dma_release_from_contiguous(dev, page, count);
+			page = NULL;
+		}
+	}
 	/* fallback */
 	if (!page)
 		page = alloc_pages_node(dev_to_node(dev), flag, get_order(size));