Commit ffcb7545 authored by Christoph Hellwig's avatar Christoph Hellwig
Browse files

dma-mapping: reject __GFP_COMP in dma_alloc_attrs 



DMA allocations can never be turned back into a page pointer, so
requesting compound pages doesn't make sense and it can't even be
supported at all by various backends.

Reject __GFP_COMP with a warning in dma_alloc_attrs, and stop clearing
the flag in the arm dma ops and dma-iommu.

Signed-off-by: default avatarChristoph Hellwig <hch@lst.de>
Acked-by: default avatarMarek Szyprowski <m.szyprowski@samsung.com>
parent 3306877a

arch/arm/mm/dma-mapping.c

+0 −17
Original line number Diff line number Diff line
@@ -564,14 +564,6 @@ static void *__dma_alloc(struct device *dev, size_t size, dma_addr_t *handle, 
	if (mask < 0xffffffffULL)

		gfp |= GFP_DMA;



	/*

	 * 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_HUGETLBFS.

	 */

	gfp &= ~(__GFP_COMP);

	args.gfp = gfp;



	*handle = DMA_MAPPING_ERROR;
@@ -1093,15 +1085,6 @@ static void *arm_iommu_alloc_attrs(struct device *dev, size_t size, 
		return __iommu_alloc_simple(dev, size, gfp, handle,

					    coherent_flag, attrs);



	/*

	 * 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_HUGETLBFS.

	 */

	gfp &= ~(__GFP_COMP);



	pages = __iommu_alloc_buffer(dev, size, gfp, attrs, coherent_flag);

	if (!pages)

		return NULL;

drivers/iommu/dma-iommu.c

+0 −3
Original line number Diff line number Diff line
@@ -744,9 +744,6 @@ static struct page **__iommu_dma_alloc_pages(struct device *dev, 
	/* IOMMU can map any pages, so himem can also be used here */

	gfp |= __GFP_NOWARN | __GFP_HIGHMEM;



	/* It makes no sense to muck about with huge pages */

	gfp &= ~__GFP_COMP;



	while (count) {

		struct page *page = NULL;

		unsigned int order_size;

kernel/dma/mapping.c

+8 −0
Original line number Diff line number Diff line
@@ -498,6 +498,14 @@ void *dma_alloc_attrs(struct device *dev, size_t size, dma_addr_t *dma_handle, 


	WARN_ON_ONCE(!dev->coherent_dma_mask);



	/*

	 * DMA allocations can never be turned back into a page pointer, so

	 * requesting compound pages doesn't make sense (and can't even be

	 * supported at all by various backends).

	 */

	if (WARN_ON_ONCE(flag & __GFP_COMP))

		return NULL;



	if (dma_alloc_from_dev_coherent(dev, size, dma_handle, &cpu_addr))

		return cpu_addr;