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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: Christoph Hellwig <hch@lst.de>
Acked-by: Marek Szyprowski <m.szyprowski@samsung.com>
This commit is contained in:
Christoph Hellwig 2022-11-09 08:37:17 +01:00
parent 3306877aff
commit ffcb754584
3 changed files with 8 additions and 20 deletions
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17
arch/arm/mm/dma-mapping.c
View File

@ -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;

3
drivers/iommu/dma-iommu.c
View File

@ -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;

8
kernel/dma/mapping.c
View File

@ -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;