2015-12-09 14:54:20

by Qais Yousef

Subject: [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 <[email protected]>
---
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

2015-12-09 15:03:12

by Mel Gorman

Subject: Re: [PATCH v2] MIPS: fix DMA contiguous allocation

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 <[email protected]>

Acked-by: Mel Gorman <[email protected]>

--
Mel Gorman
SUSE Labs