Re: [PATCH] MIPS: Fix DMA contiguous allocation

From: Sergei Shtylyov
Date: Tue Dec 08 2015 - 07:12:56 EST


On 12/8/2015 1:18 PM, 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. To verify if the flag is atomic we need to make
sure that (gfp & GFP_ATOMIC) == GFP_ATOMIC to verify that all bits rquired to

Required.

satisfy GFP_ATOMIC condition are set.

Signed-off-by: Qais Yousef <qais.yousef@xxxxxxxxxx>
---
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..d6b8a1445a3a 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) && ((gfp & GFP_ATOMIC) != GFP_ATOMIC))

() around != not necessary.

[...]

MBR, Sergei

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