From: Andrew Morton <akpm@linux-foundation.org>
To: Qais Yousef <qais.yousef@imgtec.com>
Cc: linux-mips@linux-mips.org, linux-mm@kvack.org,
linux-kernel@vger.kernel.org, ralf@linux-mips.org,
mgorman@techsingularity.net
Subject: Re: [PATCH] MIPS: Fix DMA contiguous allocation
Date: Tue, 8 Dec 2015 14:19:39 -0800 [thread overview]
Message-ID: <20151208141939.d0edbb72b3c15844c5ac25ea@linux-foundation.org> (raw)
In-Reply-To: <1449569930-2118-1-git-send-email-qais.yousef@imgtec.com>
On Tue, 8 Dec 2015 10:18:50 +0000 Qais Yousef <qais.yousef@imgtec.com> 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
> satisfy GFP_ATOMIC condition are set.
>
> ...
>
> --- 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))
> page = dma_alloc_from_contiguous(dev,
> count, get_order(size));
> if (!page)
hm. It seems that the code is asking "can I do a potentially-sleeping
memory allocation"?
The way to do that under the new regime is
if (IS_ENABLED(CONFIG_DMA_CMA) && gfpflags_allow_blocking(gfp))
Mel, can you please confirm?
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next prev parent reply other threads:[~2015-12-08 22:19 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-12-08 10:18 [PATCH] MIPS: Fix DMA contiguous allocation Qais Yousef
2015-12-08 12:12 ` Sergei Shtylyov
2015-12-08 22:19 ` Andrew Morton [this message]
2015-12-09 11:36 ` Mel Gorman
2015-12-09 14:32 ` Qais Yousef
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