[PATCH v2 22/22] ARM: dma-mapping: Drop GFP_COMP for DMA memory allocations

[Hiroshi Doyu]

arm_iommu_alloc_attrs wants to split pages after allocation in order
to reduce the memory footprint. This does not work well with GFP_COMP
pages, so drop this flag before allocation.

(ref: ea2e7057c0234cfb8b09467d8f137760d371fc72)

Signed-off-by: Hiroshi Doyu <hdoyu at nvidia.com>
---
 arch/arm/mm/dma-mapping.c |    7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/arch/arm/mm/dma-mapping.c b/arch/arm/mm/dma-mapping.c
index 7f9b179..cad35a3 100644
--- a/arch/arm/mm/dma-mapping.c
+++ b/arch/arm/mm/dma-mapping.c
@@ -1322,6 +1322,13 @@ static void *arm_iommu_alloc_attrs(struct device *dev, size_t size,
 	struct page **pages;
 	void *addr = NULL;
 
+	/* Following is a work-around (a.k.a. hack) to prevent pages
+	 * with __GFP_COMP being passed to split_page() which cannot
+	 * handle them.  The real problem is that this flag probably
+	 * should be 0 on ARM as it is not supported on this
+	 * platform--see CONFIG_HUGETLB_PAGE. */
+	gfp &= ~(__GFP_COMP);
+
 	*handle = DMA_ERROR_CODE;
 	size = PAGE_ALIGN(size);
 
-- 
1.7.9.5