[PATCH] ARM: dma-mapping: always clear allocated buffers

[PATCH] ARM: dma-mapping: always clear allocated buffers

[YueHaibing]

Sean Wang report dma_zalloc_coherent doesn't work as expect on his
armv7,the allocated mem is not zeroed.The reason is __alloc_from_pool
doesn't honor __GFP_ZERO.

Like commit 6829e274a623 ("arm64: dma-mapping: always clear allocated buffers")
does,always clear allocated buffers to fix this.

Reported-by: Sean Wang <sean.wang@mediatek.com>
Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Reviewed-by: zhong jiang <zhongjiang@huawei.com>
---
 arch/arm/mm/dma-mapping.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/arm/mm/dma-mapping.c b/arch/arm/mm/dma-mapping.c
index 6656647..cf5882f 100644
--- a/arch/arm/mm/dma-mapping.c
+++ b/arch/arm/mm/dma-mapping.c
@@ -564,6 +564,7 @@ static void *__alloc_from_pool(size_t size, struct page **ret_page)
 
 		*ret_page = phys_to_page(phys);
 		ptr = (void *)val;
+		memset(ptr, 0, size);
 	}
 
 	return ptr;
-- 
2.7.0

Re: [PATCH] ARM: dma-mapping: always clear allocated buffers

[Christoph Hellwig]

On Tue, Jul 24, 2018 at 10:04:35PM +0800, YueHaibing wrote:
> Sean Wang report dma_zalloc_coherent doesn't work as expect on his
> armv7,the allocated mem is not zeroed.The reason is __alloc_from_pool
> doesn't honor __GFP_ZERO.

Please explain the "why" a little more.  All the explanations are in
the referenced arm64 commit and should be mentioned here as well.

Re: [PATCH] ARM: dma-mapping: always clear allocated buffers

[YueHaibing]

On 2018/7/25 2:09, Christoph Hellwig wrote:
> On Tue, Jul 24, 2018 at 10:04:35PM +0800, YueHaibing wrote:
>> Sean Wang report dma_zalloc_coherent doesn't work as expect on his
>> armv7,the allocated mem is not zeroed.The reason is __alloc_from_pool
>> doesn't honor __GFP_ZERO.
> 
> Please explain the "why" a little more.  All the explanations are in
> the referenced arm64 commit and should be mentioned here as well.

ok, will send v2.

> 
> .
>