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[PATCH v2] MIPS: fix DMA contiguous allocation

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  [PATCH v2] MIPS: fix DMA contiguous allocation Qais Yousef <qais.yousef@imgtec.com> - 2015-12-09 16:00 +0100
    Re: [PATCH v2] MIPS: fix DMA contiguous allocation Mel Gorman <mgorman@techsingularity.net> - 2015-12-09 16:10 +0100

#1287541 — [PATCH v2] MIPS: fix DMA contiguous allocation

Recent changes to how GFP_ATOMIC is defined seems to have broken the condition
to use mips_alloc_from_contiguous() in mips_dma_alloc_coherent().

I couldn't bottom out the exact change but I think it's this one

d0164adc89f6 (mm, page_alloc: distinguish between being unable to sleep,
unwilling to sleep and avoiding waking kswapd)

From what I see GFP_ATOMIC has multiple bits set and the check for !(gfp
& GFP_ATOMIC) isn't enough.

The reason behind this condition is to check whether we can potentially do
a sleeping memory allocation. Use gfpflags_allow_blocking() instead which
should be more robust.

Signed-off-by: Qais Yousef <qais.yousef@imgtec.com>
---
 arch/mips/mm/dma-default.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/mips/mm/dma-default.c b/arch/mips/mm/dma-default.c
index d8117be729a2..730d394ce5f0 100644
--- a/arch/mips/mm/dma-default.c
+++ b/arch/mips/mm/dma-default.c
@@ -145,7 +145,7 @@ static void *mips_dma_alloc_coherent(struct device *dev, size_t size,
 
 	gfp = massage_gfp_flags(dev, gfp);
 
-	if (IS_ENABLED(CONFIG_DMA_CMA) && !(gfp & GFP_ATOMIC))
+	if (IS_ENABLED(CONFIG_DMA_CMA) && gfpflags_allow_blocking(gfp))
 		page = dma_alloc_from_contiguous(dev,
 					count, get_order(size));
 	if (!page)
-- 
2.1.0

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#1287548

On Wed, Dec 09, 2015 at 02:54:05PM +0000, Qais Yousef wrote:
> Recent changes to how GFP_ATOMIC is defined seems to have broken the condition
> to use mips_alloc_from_contiguous() in mips_dma_alloc_coherent().
> 
> I couldn't bottom out the exact change but I think it's this one
> 
> d0164adc89f6 (mm, page_alloc: distinguish between being unable to sleep,
> unwilling to sleep and avoiding waking kswapd)
> 
> From what I see GFP_ATOMIC has multiple bits set and the check for !(gfp
> & GFP_ATOMIC) isn't enough.
> 
> The reason behind this condition is to check whether we can potentially do
> a sleeping memory allocation. Use gfpflags_allow_blocking() instead which
> should be more robust.
> 
> Signed-off-by: Qais Yousef <qais.yousef@imgtec.com>

Acked-by: Mel Gorman <mgorman@techsingularity.net>

-- 
Mel Gorman
SUSE Labs
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